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How to clear the canvas without interrupting animations?

I am visualising flight paths with D3 and Canvas. In short, I have data for each flight's origin and destination
as well as the airport coordinates. The ideal end state is to have an indiviudal circle representing a plane moving
along each flight path from origin to destination. The current state is that each circle gets visualised along the path,
yet the removal of the previous circle along the line does not work as clearRect gets called nearly constantly.
Current state:
Ideal state (achieved with SVG):
The Concept
Conceptually, an SVG path for each flight is produced in memory using D3's custom interpolation with path.getTotalLength() and path.getPointAtLength() to move the circle along the path.
The interpolator returns the points along the path at any given time of the transition. A simple drawing function takes these points and draws the circle.
Key functions
The visualisation gets kicked off with:
od_pairs.forEach(function(el, i) {
fly(el[0], el[1]); // for example: fly('LHR', 'JFK')
});
The fly() function creates the SVG path in memory and a D3 selection of a circle (the 'plane') - also in memory.
function fly(origin, destination) {
var pathElement = document.createElementNS(d3.namespaces.svg, 'path');
var routeInMemory = d3.select(pathElement)
.datum({
type: 'LineString',
coordinates: [airportMap[origin], airportMap[destination]]
})
.attr('d', path);
var plane = custom.append('plane');
transition(plane, routeInMemory.node());
}
The plane gets transitioned along the path by the custom interpolater in the delta() function:
function transition(plane, route) {
var l = route.getTotalLength();
plane.transition()
.duration(l * 50)
.attrTween('pointCoordinates', delta(plane, route))
// .on('end', function() { transition(plane, route); });
}
function delta(plane, path) {
var l = path.getTotalLength();
return function(i) {
return function(t) {
var p = path.getPointAtLength(t * l);
draw([p.x, p.y]);
};
};
}
... which calls the simple draw() function
function draw(coords) {
// contextPlane.clearRect(0, 0, width, height); << how to tame this?
contextPlane.beginPath();
contextPlane.arc(coords[0], coords[1], 1, 0, 2*Math.PI);
contextPlane.fillStyle = 'tomato';
contextPlane.fill();
}
This results in an extending 'path' of circles as the circles get drawn yet not removed as shown in the first gif above.
Full code here: http://blockbuilder.org/larsvers/8e25c39921ca746df0c8995cce20d1a6
My question is, how can I achieve to draw only a single, current circle while the previous circle gets removed without interrupting other circles being drawn on the same canvas?
Some failed attempts:
The natural answer is of course context.clearRect(), however, as there's a time delay (roughly a milisecond+) for each circle to be drawn as it needs to get through the function pipeline clearRect gets fired almost constantly.
I tried to tame the perpetual clearing of the canvas by calling clearRect only at certain intervals (Date.now() % 10 === 0 or the like) but that leads to no good either.
Another thought was to calculate the previous circle's position and remove the area specifically with a small and specific clearRect definition within each draw() function.
Any pointers very much appreciated.

Handling small dirty regions, especially if there is overlap between objects quickly becomes very computationally heavy.
As a general rule, a average Laptop/desktop can easily handle 800 animated objects if the computation to calculate position is simple.
This means that the simple way to animate is to clear the canvas and redraw every frame. Saves a lot of complex code that offers no advantage over the simple clear and redraw.
const doFor = (count,callback) => {var i=0;while(i < count){callback(i++)}};
function createIcon(drawFunc){
const icon = document.createElement("canvas");
icon.width = icon.height = 10;
drawFunc(icon.getContext("2d"));
return icon;
}
function drawPlane(ctx){
const cx = ctx.canvas.width / 2;
const cy = ctx.canvas.height / 2;
ctx.beginPath();
ctx.strokeStyle = ctx.fillStyle = "red";
ctx.lineWidth = cx / 2;
ctx.lineJoin = "round";
ctx.lineCap = "round";
ctx.moveTo(cx/2,cy)
ctx.lineTo(cx * 1.5,cy);
ctx.moveTo(cx,cy/2)
ctx.lineTo(cx,cy*1.5)
ctx.stroke();
ctx.lineWidth = cx / 4;
ctx.moveTo(cx * 1.7,cy * 0.6)
ctx.lineTo(cx * 1.7,cy*1.4)
ctx.stroke();
}
const planes = {
items : [],
icon : createIcon(drawPlane),
clear(){
planes.items.length = 0;
},
add(x,y){
planes.items.push({
x,y,
ax : 0, // the direction of the x axis of this plane
ay : 0,
dir : Math.random() * Math.PI * 2,
speed : Math.random() * 0.2 + 0.1,
dirV : (Math.random() - 0.5) * 0.01, // change in direction
})
},
update(){
var i,p;
for(i = 0; i < planes.items.length; i ++){
p = planes.items[i];
p.dir += p.dirV;
p.ax = Math.cos(p.dir);
p.ay = Math.sin(p.dir);
p.x += p.ax * p.speed;
p.y += p.ay * p.speed;
}
},
draw(){
var i,p;
const w = canvas.width;
const h = canvas.height;
for(i = 0; i < planes.items.length; i ++){
p = planes.items[i];
var x = ((p.x % w) + w) % w;
var y = ((p.y % h) + h) % h;
ctx.setTransform(-p.ax,-p.ay,p.ay,-p.ax,x,y);
ctx.drawImage(planes.icon,-planes.icon.width / 2,-planes.icon.height / 2);
}
}
}
const ctx = canvas.getContext("2d");
function mainLoop(){
if(canvas.width !== innerWidth || canvas.height !== innerHeight){
canvas.width = innerWidth;
canvas.height = innerHeight;
planes.clear();
doFor(800,()=>{ planes.add(Math.random() * canvas.width, Math.random() * canvas.height) })
}
ctx.setTransform(1,0,0,1,0,0);
// clear or render a background map
ctx.clearRect(0,0,canvas.width,canvas.height);
planes.update();
planes.draw();
requestAnimationFrame(mainLoop)
}
requestAnimationFrame(mainLoop)
canvas {
position : absolute;
top : 0px;
left : 0px;
}
<canvas id=canvas></canvas>
800 animated points
As pointed out in the comments some machines may be able to draw a circle if one colour and all as one path slightly quicker (not all machines). The point of rendering an image is that it is invariant to the image complexity. Image rendering is dependent on the image size but colour and alpha setting per pixel have no effect on rendering speed. Thus I have changed the circle to show the direction of each point via a little plane icon.
Path follow example
I have added a way point object to each plane that in the demo has a random set of way points added. I called it path (could have used a better name) and a unique path is created for each plane.
The demo is to just show how you can incorporate the D3.js interpolation into the plane update function. The plane.update now calls the path.getPos(time) which returns true if the plane has arrived. If so the plane is remove. Else the new plane coordinates are used (stored in the path object for that plane) to set the position and direction.
Warning the code for path does little to no vetting and thus can easily be made to throw an error. It is assumed that you write the path interface to the D3.js functionality you want.
const doFor = (count,callback) => {var i=0;while(i < count){callback(i++)}};
function createIcon(drawFunc){
const icon = document.createElement("canvas");
icon.width = icon.height = 10;
drawFunc(icon.getContext("2d"));
return icon;
}
function drawPlane(ctx){
const cx = ctx.canvas.width / 2;
const cy = ctx.canvas.height / 2;
ctx.beginPath();
ctx.strokeStyle = ctx.fillStyle = "red";
ctx.lineWidth = cx / 2;
ctx.lineJoin = "round";
ctx.lineCap = "round";
ctx.moveTo(cx/2,cy)
ctx.lineTo(cx * 1.5,cy);
ctx.moveTo(cx,cy/2)
ctx.lineTo(cx,cy*1.5)
ctx.stroke();
ctx.lineWidth = cx / 4;
ctx.moveTo(cx * 1.7,cy * 0.6)
ctx.lineTo(cx * 1.7,cy*1.4)
ctx.stroke();
}
const path = {
wayPoints : null, // holds way points
nextTarget : null, // holds next target waypoint
current : null, // hold previously passed way point
x : 0, // current pos x
y : 0, // current pos y
addWayPoint(x,y,time){
this.wayPoints.push({x,y,time});
},
start(){
if(this.wayPoints.length > 1){
this.current = this.wayPoints.shift();
this.nextTarget = this.wayPoints.shift();
}
},
getNextTarget(){
this.current = this.nextTarget;
if(this.wayPoints.length === 0){ // no more way points
return;
}
this.nextTarget = this.wayPoints.shift(); // get the next target
},
getPos(time){
while(this.nextTarget.time < time && this.wayPoints.length > 0){
this.getNextTarget(); // get targets untill the next target is ahead in time
}
if(this.nextTarget.time < time){
return true; // has arrivecd at target
}
// get time normalised ove time between current and next
var timeN = (time - this.current.time) / (this.nextTarget.time - this.current.time);
this.x = timeN * (this.nextTarget.x - this.current.x) + this.current.x;
this.y = timeN * (this.nextTarget.y - this.current.y) + this.current.y;
return false; // has not arrived
}
}
const planes = {
items : [],
icon : createIcon(drawPlane),
clear(){
planes.items.length = 0;
},
add(x,y){
var p;
planes.items.push(p = {
x,y,
ax : 0, // the direction of the x axis of this plane
ay : 0,
path : Object.assign({},path,{wayPoints : []}),
})
return p; // return the plane
},
update(time){
var i,p;
for(i = 0; i < planes.items.length; i ++){
p = planes.items[i];
if(p.path.getPos(time)){ // target reached
planes.items.splice(i--,1); // remove
}else{
p.dir = Math.atan2(p.y - p.path.y, p.x - p.path.x) + Math.PI; // add 180 because i drew plane wrong way around.
p.ax = Math.cos(p.dir);
p.ay = Math.sin(p.dir);
p.x = p.path.x;
p.y = p.path.y;
}
}
},
draw(){
var i,p;
const w = canvas.width;
const h = canvas.height;
for(i = 0; i < planes.items.length; i ++){
p = planes.items[i];
var x = ((p.x % w) + w) % w;
var y = ((p.y % h) + h) % h;
ctx.setTransform(-p.ax,-p.ay,p.ay,-p.ax,x,y);
ctx.drawImage(planes.icon,-planes.icon.width / 2,-planes.icon.height / 2);
}
}
}
const ctx = canvas.getContext("2d");
function mainLoop(time){
if(canvas.width !== innerWidth || canvas.height !== innerHeight){
canvas.width = innerWidth;
canvas.height = innerHeight;
planes.clear();
doFor(810,()=>{
var p = planes.add(Math.random() * canvas.width, Math.random() * canvas.height);
// now add random number of way points
var timeP = time;
// info to create a random path
var dir = Math.random() * Math.PI * 2;
var x = p.x;
var y = p.y;
doFor(Math.floor(Math.random() * 80 + 12),()=>{
var dist = Math.random() * 5 + 4;
x += Math.cos(dir) * dist;
y += Math.sin(dir) * dist;
dir += (Math.random()-0.5)*0.3;
timeP += Math.random() * 1000 + 500;
p.path.addWayPoint(x,y,timeP);
});
// last waypoin at center of canvas.
p.path.addWayPoint(canvas.width / 2,canvas.height / 2,timeP + 5000);
p.path.start();
})
}
ctx.setTransform(1,0,0,1,0,0);
// clear or render a background map
ctx.clearRect(0,0,canvas.width,canvas.height);
planes.update(time);
planes.draw();
requestAnimationFrame(mainLoop)
}
requestAnimationFrame(mainLoop)
canvas {
position : absolute;
top : 0px;
left : 0px;
}
<canvas id=canvas></canvas>
800 animated points

#Blindman67 is correct, clear and redraw everything, every frame.
I'm here just to say that when dealing with such primitive shapes as arc without too many color variations, it's actually better to use the arc method than drawImage().
The idea is to wrap all your shapes in a single path declaration, using
ctx.beginPath(); // start path declaration
for(i; i<shapes.length; i++){ // loop through our points
ctx.moveTo(pt.x + pt.radius, pt.y); // default is lineTo and we don't want it
// Note the '+ radius', arc starts at 3 o'clock
ctx.arc(pt.x, pt.y, pt.radius, 0, Math.PI*2);
}
ctx.fill(); // a single fill()
This is faster than drawImage, but the main caveat is that it works only for single-colored set of shapes.
I've made an complex plotting app, where I do draw a lot (20K+) of entities, with animated positions. So what I do, is to store two sets of points, one un-sorted (actually sorted by radius), and one
sorted by color. I then do use the sorted-by-color one in my animations loop, and when the animation is complete, I draw only the final frame with the sorted-by-radius (after I filtered the non visible entities). I achieve 60fps on most devices. When I tried with drawImage, I was stuck at about 10fps for 5K points.
Here is a modified version of Blindman67's good answer's snippet, using this single-path approach.
/* All credits to SO user Blindman67 */
const doFor = (count,callback) => {var i=0;while(i < count){callback(i++)}};
const planes = {
items : [],
clear(){
planes.items.length = 0;
},
add(x,y){
planes.items.push({
x,y,
rad: 2,
dir : Math.random() * Math.PI * 2,
speed : Math.random() * 0.2 + 0.1,
dirV : (Math.random() - 0.5) * 0.01, // change in direction
})
},
update(){
var i,p;
for(i = 0; i < planes.items.length; i ++){
p = planes.items[i];
p.dir += p.dirV;
p.x += Math.cos(p.dir) * p.speed;
p.y += Math.sin(p.dir) * p.speed;
}
},
draw(){
var i,p;
const w = canvas.width;
const h = canvas.height;
ctx.beginPath();
ctx.fillStyle = 'red';
for(i = 0; i < planes.items.length; i ++){
p = planes.items[i];
var x = ((p.x % w) + w) % w;
var y = ((p.y % h) + h) % h;
ctx.moveTo(x + p.rad, y)
ctx.arc(x, y, p.rad, 0, Math.PI*2);
}
ctx.fill();
}
}
const ctx = canvas.getContext("2d");
function mainLoop(){
if(canvas.width !== innerWidth || canvas.height !== innerHeight){
canvas.width = innerWidth;
canvas.height = innerHeight;
planes.clear();
doFor(8000,()=>{ planes.add(Math.random() * canvas.width, Math.random() * canvas.height) })
}
ctx.setTransform(1,0,0,1,0,0);
// clear or render a background map
ctx.clearRect(0,0,canvas.width,canvas.height);
planes.update();
planes.draw();
requestAnimationFrame(mainLoop)
}
requestAnimationFrame(mainLoop)
canvas {
position : absolute;
top : 0px;
left : 0px;
z-index: -1;
}
<canvas id=canvas></canvas>
8000 animated points
Not directly related but in case you've got part of your drawings that don't update at the same rate as the rest (e.g if you want to highlight an area of your map...) then you might also consider separating your drawings in different layers, on offscreen canvases. This way you'd have one canvas for the planes, that you'd clear every frame, and other canvas for other layers that you would update at different rate. But that's an other story.

Calculating angular velocity after a collision

I've got the linear component of collision resolution down relatively well, but I can't quite figure out how to do the same for the angular one. From what I've read, it's something like... torque = point of collision x linear velocity. (cross product) I tried to incorporate an example I found into my code but I actually don't see any rotation at all when objects collide. The other fiddle works perfectly with a rudimentary implementation of the seperating axis theorem and the angular velocity calculations. Here's what I've come up with...
Property definitions (orientation, angular velocity, and angular acceleration):
rotation: 0,
angularVelocity: 0,
angularAcceleration: 0
Calculating the angular velocity in the collision response:
var pivotA = this.vector(bodyA.x, bodyA.y);
bodyA.angularVelocity = 1 * 0.2 * (bodyA.angularVelocity / Math.abs(bodyA.angularVelocity)) * pivotA.subtract(isCircle ? pivotA.add(bodyA.radius) : {
x: pivotA.x + boundsA.width,
y: pivotA.y + boundsA.height
}).vCross(bodyA.velocity);
var pivotB = this.vector(bodyB.x, bodyB.y);
bodyB.angularVelocity = 1 * 0.2 * (bodyB.angularVelocity / Math.abs(bodyB.angularVelocity)) * pivotB.subtract(isCircle ? pivotB.add(bodyB.radius) : {
x: pivotB.x + boundsB.width,
y: pivotB.y + boundsB.height
}).vCross(bodyB.velocity);
Updating the orientation in the update loop:
var torque = 0;
torque += core.objects[o].angularVelocity * -1;
core.objects[o].angularAcceleration = torque / core.objects[o].momentOfInertia();
core.objects[o].angularVelocity += core.objects[o].angularAcceleration;
core.objects[o].rotation += core.objects[o].angularVelocity;
I would post the code that I have for calculating the moments of inertia but there's a seperate one for every object so that would be a bit... lengthy. Nonetheless, here's the one for a circle as an example:
return this.mass * this.radius * this.radius / 2;
Just to show the result, here's my fiddle. As shown, objects do not rotate on collision. (not exactly visible with the circles, but it should work for the zero and seven)
What am I doing wrong?
EDIT: Reason they weren't rotating at all was because of an error with groups in the response function -- it rotates now, just not correctly. However, I've commented that out for now as it messes things up.
Also, I've tried another method for rotation. Here's the code in the response:
_bodyA.angularVelocity = direction.vCross(_bodyA.velocity) / (isCircle ? _bodyA.radius : boundsA.width);
_bodyB.angularVelocity = direction.vCross(_bodyB.velocity) / (isCircle ? _bodyB.radius : boundsB.width);
Note that direction refers to the "collision normal".

Angular and linear acceleration due to force vector
Angular and directional accelerations due to an applied force are two components of the same thing and can not be separated. To get one you need to solve for both.
Define the calculations
From simple physics and standing on shoulders we know the following.
F is force (equivalent to inertia)
Fv is linear force
Fa is angular force
a is acceleration could be linear or rotational depending on where it is used
v is velocity. For angular situations it is the tangential component only
m is mass
r is radius
For linear forces
F = m * v
From which we derive
m = F / v
v = F / m
For rotational force (v is tangential velocity)
F = r * r * m * (v / r) and simplify F = r * m * v
From which we derive
m = F / ( r * v )
v = F / ( r * m )
r = F / ( v * m )
Because the forces we apply are instantaneous we can interchange a acceleration and v velocity to give all the following formulas
Linear
F = m * a
m = F / a
a = F / m
Rotational
F = r * m * a
m = F / ( r * a )
a = F / ( r * m )
r = F / ( a * m )
As we are only interested in the change in velocity for both linear and rotation solutions
a1 = F / m
a2 = F / ( r * m )
Where a1 is acceleration in pixels per frame2 and a2 is acceleration in radians per frame2 ( the frame squared just denotes it is acceleration)
From 1D to 2D
Because this is a 2D solution and all above are 1D we need to use vectors. I for this problem use two forms of the 2D vector. Polar that has a magnitude (length, distance, the like...) and direction. Cartesian which has x and y. What a vector represents depends on how it is used.
The following functions are used as helpers in the solution. They are written in ES6 so for non compliant browsers you will have to adapt them, though I would not ever suggest you use these as they are written for convenience, they are very inefficient and do a lot of redundant calculations.
Converts a vector from polar to cartesian returning a new one
function polarToCart(pVec, retV = {x : 0, y : 0}) {
retV.x = Math.cos(pVec.dir) * pVec.mag;
retV.y = Math.sin(pVec.dir) * pVec.mag;
return retV;
}
Converts a vector from cartesian to polar returning a new one
function cartToPolar(vec, retV = {dir : 0, mag : 0}) {
retV.dir = Math.atan2(vec.y, vec.x);
retV.mag = Math.hypot(vec.x, vec.y);
return retV;
}
Creates a polar vector
function polar(mag = 1, dir = 0) {
return validatePolar({dir : dir,mag : mag});
}
Create a vector as a cartesian
function vector(x = 1, y = 0) {
return {x : x, y : y};
}
True is the arg vec is a vector in polar form
function isPolar(vec) {
if (vec.mag !== undefined && vec.dir !== undefined) {return true;}
return false;
}
Returns true if arg vec is a vector in cartesian form
function isCart(vec) {
if (vec.x !== undefined && vec.y !== undefined) {return true;}
return false;
}
Returns a new vector in polar form also ensures that vec.mag is positive
function asPolar(vec){
if(isCart(vec)){ return cartToPolar(vec); }
if(vec.mag < 0){
vec.mag = - vec.mag;
vec.dir += PI;
}
return { dir : vec.dir, mag : vec.mag };
}
Copy and converts an unknown vec to cart if not already
function asCart(vec){
if(isPolar(vec)){ return polarToCart(vec); }
return { x : vec.x, y : vec.y};
}
Calculations can result in a negative magnitude though this is valid for some calculations this results in the incorrect vector (reversed) this simply validates that the polar vector has a positive magnitude it does not change the vector just the sign and direction
function validatePolar(vec) {
if (isPolar(vec)) {
if (vec.mag < 0) {
vec.mag = - vec.mag;
vec.dir += PI;
}
}
return vec;
}
The Box
Now we can define an object that we can use to play with. A simple box that has position, size, mass, orientation, velocity and rotation
function createBox(x,y,w,h){
var box = {
x : x, // pos
y : y,
r : 0.1, // its rotation AKA orientation or direction in radians
h : h, // its height
w : w, // its width
dx : 0, // delta x in pixels per frame 1/60th second
dy : 0, // delta y
dr : 0.0, // deltat rotation in radians per frame 1/60th second
mass : w * h, // mass in things
update :function(){
this.x += this.dx;
this.y += this.dy;
this.r += this.dr;
},
}
return box;
}
Applying a force to an object
So now we can redefine some terms
F (force) is a vector force the magnitude is the force and it has a direction
var force = polar(100,0); // create a force 100 units to the right (0 radians)
The force is meaningless without a position where it is applied.
Position is a vector that just holds and x and y location
var location = vector(canvas.width/2, canvas.height/2); // defines a point in the middle of the canvas
Directional vector holds the direction and distance between to positional vectors
var l1 = vector(canvas.width/2, canvas.height/2); // defines a point in the middle of the canvas
var l2 = vector(100,100);
var direction = asPolar(vector(l2.x - l1.x, l2.y - l1.y)); // get the direction as polar vector
direction now has the direction from canvas center to point (100,100) and the distance.
The last thing we need to do is extract the components from a force vector along a directional vector. When you apply a force to an object the force is split into two, one is the force along the line to the object center and adds to the object acceleration, the other force is at 90deg to the line to the object center (the tangent) and that is the force that changes rotation.
To get the two components you get the difference in direction between the force vector and the directional vector from where the force is applied to the object center.
var force = polar(100,0); // the force
var forceLoc = vector(50,50); // the location the force is applied
var direction2Center = asPolar(vector(box.x - forceLoc.x, box.y - forceLoc.y)); // get the direction as polar vector
var pheta = direction2Center - force.dir; // get the angle between the force and object center
Now that you have that angle pheta the force can be split into its rotational and linear components with trig.
var F = force.mag; // get the force magnitude
var Fv = Math.cos(pheta) * F; // get the linear force
var Fa = Math.sin(pheta) * F; // get the angular force
Now the forces can be converted back to accelerations for linear a = F/m and angular a = F/(m*r)
accelV = Fv / box.mass; // linear acceleration in pixels
accelA = Fa / (box.mass * direction2Center.mag); // angular acceleration in radians
You then convert the linear force back to a vector that has a direction to the center of the object
var forceV = polar(Fv, direction2Center);
Convert is back to the cartesian so we can add it to the object deltaX and deltaY
forceV = asCart(forceV);
And add the acceleration to the box
box.dx += forceV.x;
box.dy += forceV.y;
Rotational acceleration is just one dimensional so just add it to the delta rotation of the box
box.dr += accelA;
And that is it.
Function to apply force to Box
The function if attached to the box will apply a force vector at a location to the box.
Attach to the box like so
box.applyForce = applyForce; // bind function to the box;
You can then call the function via the box
box.applyForce(force, locationOfForce);
function applyForce(force, loc){ // force is a vector, loc is a coordinate
var toCenter = asPolar(vector(this.x - loc.x, this.y - loc.y)); // get the vector to the center
var pheta = toCenter.dir - force.dir; // get the angle between the force and the line to center
var Fv = Math.cos(pheta) * force.mag; // Split the force into the velocity force along the line to the center
var Fa = Math.sin(pheta) * force.mag; // and the angular force at the tangent to the line to the center
var accel = asPolar(toCenter); // copy the direction to center
accel.mag = Fv / this.mass; // now use F = m * a in the form a = F/m to get acceleration
var deltaV = asCart(accel); // convert acceleration to cartesian
this.dx += deltaV.x // update the box delta V
this.dy += deltaV.y //
var accelA = Fa / (toCenter.mag * this.mass); // for the angular component get the rotation
// acceleration from F=m*a*r in the
// form a = F/(m*r)
this.dr += accelA;// now add that to the box delta r
}
The Demo
The demo is only about the function applyForce the stuff to do with gravity and bouncing are only very bad approximations and should not be used for any physic type of stuff as they do not conserve energy.
Click and drag to apply a force to the object in the direction that the mouse is moved.
const PI90 = Math.PI / 2;
const PI = Math.PI;
const PI2 = Math.PI * 2;
const INSET = 10; // playfeild inset
const ARROW_SIZE = 6
const SCALE_VEC = 10;
const SCALE_FORCE = 0.15;
const LINE_W = 2;
const LIFE = 12;
const FONT_SIZE = 20;
const FONT = "Arial Black";
const WALL_NORMS = [PI90,PI,-PI90,0]; // dirction of the wall normals
var box = createBox(200, 200, 50, 100);
box.applyForce = applyForce; // Add this function to the box
// render / update function
var mouse = (function(){
function preventDefault(e) { e.preventDefault(); }
var i;
var mouse = {
x : 0, y : 0,buttonRaw : 0,
bm : [1, 2, 4, 6, 5, 3], // masks for setting and clearing button raw bits;
mouseEvents : "mousemove,mousedown,mouseup".split(",")
};
function mouseMove(e) {
var t = e.type, m = mouse;
m.x = e.offsetX; m.y = e.offsetY;
if (m.x === undefined) { m.x = e.clientX; m.y = e.clientY; }
if (t === "mousedown") { m.buttonRaw |= m.bm[e.which-1];
} else if (t === "mouseup") { m.buttonRaw &= m.bm[e.which + 2];}
e.preventDefault();
}
mouse.start = function(element = document){
if(mouse.element !== undefined){ mouse.removeMouse();}
mouse.element = element;
mouse.mouseEvents.forEach(n => { element.addEventListener(n, mouseMove); } );
}
mouse.remove = function(){
if(mouse.element !== undefined){
mouse.mouseEvents.forEach(n => { mouse.element.removeEventListener(n, mouseMove); } );
mouse.element = undefined;
}
}
return mouse;
})();
var canvas,ctx;
function createCanvas(){
canvas = document.createElement("canvas");
canvas.style.position = "absolute";
canvas.style.left = "0px";
canvas.style.top = "0px";
canvas.style.zIndex = 1000;
document.body.appendChild(canvas);
}
function resizeCanvas(){
if(canvas === undefined){
createCanvas();
}
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
ctx = canvas.getContext("2d");
if(box){
box.w = canvas.width * 0.10;
box.h = box.w * 2;
box.mass = box.w * box.h;
}
}
window.addEventListener("resize",resizeCanvas);
resizeCanvas();
mouse.start(canvas)
var tempVecs = [];
function addTempVec(v,vec,col,life = LIFE,scale = SCALE_VEC){tempVecs.push({v:v,vec:vec,col:col,scale:scale,life:life,sLife:life});}
function drawTempVecs(){
for(var i = 0; i < tempVecs.length; i ++ ){
var t = tempVecs[i]; t.life -= 1;
if(t.life <= 0){tempVecs.splice(i, 1); i--; continue}
ctx.globalAlpha = (t.life / t.sLife)*0.25;
drawVec(t.v, t.vec ,t.col, t.scale)
}
}
function drawVec(v,vec,col,scale = SCALE_VEC){
vec = asPolar(vec)
ctx.setTransform(1,0,0,1,v.x,v.y);
var d = vec.dir;
var m = vec.mag;
ctx.rotate(d);
ctx.beginPath();
ctx.lineWidth = LINE_W;
ctx.strokeStyle = col;
ctx.moveTo(0,0);
ctx.lineTo(m * scale,0);
ctx.moveTo(m * scale-ARROW_SIZE,-ARROW_SIZE);
ctx.lineTo(m * scale,0);
ctx.lineTo(m * scale-ARROW_SIZE,ARROW_SIZE);
ctx.stroke();
}
function drawText(text,x,y,font,size,col){
ctx.font = size + "px "+font;
ctx.textAlign = "center";
ctx.textBaseline = "middle";
ctx.setTransform(1,0,0,1,x,y);
ctx.globalAlpha = 1;
ctx.fillStyle = col;
ctx.fillText(text,0,0);
}
function createBox(x,y,w,h){
var box = {
x : x, // pos
y : y,
r : 0.1, // its rotation AKA orientation or direction in radians
h : h, // its height, and I will assume that its depth is always equal to its height
w : w, // its width
dx : 0, // delta x in pixels per frame 1/60th second
dy : 0, // delta y
dr : 0.0, // deltat rotation in radians per frame 1/60th second
getDesc : function(){
var vel = Math.hypot(this.dx ,this.dy);
var radius = Math.hypot(this.w,this.h)/2
var rVel = Math.abs(this.dr * radius);
var str = "V " + (vel*60).toFixed(0) + "pps ";
str += Math.abs(this.dr * 60 * 60).toFixed(0) + "rpm ";
str += "Va " + (rVel*60).toFixed(0) + "pps ";
return str;
},
mass : function(){ return (this.w * this.h * this.h)/1000; }, // mass in K things
draw : function(){
ctx.globalAlpha = 1;
ctx.setTransform(1,0,0,1,this.x,this.y);
ctx.rotate(this.r);
ctx.fillStyle = "#444";
ctx.fillRect(-this.w/2, -this.h/2, this.w, this.h)
ctx.strokeRect(-this.w/2, -this.h/2, this.w, this.h)
},
update :function(){
this.x += this.dx;
this.y += this.dy;
this.dy += 0.061; // alittle gravity
this.r += this.dr;
},
getPoint : function(which){
var dx,dy,x,y,xx,yy,velocityA,velocityT,velocity;
dx = Math.cos(this.r);
dy = Math.sin(this.r);
switch(which){
case 0:
x = -this.w /2;
y = -this.h /2;
break;
case 1:
x = this.w /2;
y = -this.h /2;
break;
case 2:
x = this.w /2;
y = this.h /2;
break;
case 3:
x = -this.w /2;
y = this.h /2;
break;
case 4:
x = this.x;
y = this.y;
}
var xx,yy;
xx = x * dx + y * -dy;
yy = x * dy + y * dx;
var details = asPolar(vector(xx, yy))
xx += this.x;
yy += this.y;
velocityA = polar(details.mag * this.dr, details.dir + PI90);
velocityT = vectorAdd(velocity = vector(this.dx, this.dy), velocityA);
return {
velocity : velocity, // only directional
velocityT : velocityT, // total
velocityA : velocityA, // angular only
pos : vector(xx, yy),
radius : details.mag,
}
},
}
box.mass = box.mass(); // Mass remains the same so just set it with its function
return box;
}
// calculations can result in a negative magnitude though this is valide for some
// calculations this results in the incorrect vector (reversed)
// this simply validates that the polat vector has a positive magnitude
// it does not change the vector just the sign and direction
function validatePolar(vec){
if(isPolar(vec)){
if(vec.mag < 0){
vec.mag = - vec.mag;
vec.dir += PI;
}
}
return vec;
}
// converts a vector from polar to cartesian returning a new one
function polarToCart(pVec, retV = {x : 0, y : 0}){
retV.x = Math.cos(pVec.dir) * pVec.mag;
retV.y = Math.sin(pVec.dir) * pVec.mag;
return retV;
}
// converts a vector from cartesian to polar returning a new one
function cartToPolar(vec, retV = {dir : 0, mag : 0}){
retV.dir = Math.atan2(vec.y,vec.x);
retV.mag = Math.hypot(vec.x,vec.y);
return retV;
}
function polar (mag = 1, dir = 0) { return validatePolar({dir : dir, mag : mag}); } // create a polar vector
function vector (x= 1, y= 0) { return {x: x, y: y}; } // create a cartesian vector
function isPolar (vec) { if(vec.mag !== undefined && vec.dir !== undefined) { return true; } return false; }// returns true if polar
function isCart (vec) { if(vec.x !== undefined && vec.y !== undefined) { return true; } return false; }// returns true if cartesian
// copy and converts an unknown vec to polar if not already
function asPolar(vec){
if(isCart(vec)){ return cartToPolar(vec); }
if(vec.mag < 0){
vec.mag = - vec.mag;
vec.dir += PI;
}
return { dir : vec.dir, mag : vec.mag };
}
// copy and converts an unknown vec to cart if not already
function asCart(vec){
if(isPolar(vec)){ return polarToCart(vec); }
return { x : vec.x, y : vec.y};
}
// normalise makes a vector a unit length and returns it as a cartesian
function normalise(vec){
var vp = asPolar(vec);
vap.mag = 1;
return asCart(vp);
}
function vectorAdd(vec1, vec2){
var v1 = asCart(vec1);
var v2 = asCart(vec2);
return vector(v1.x + v2.x, v1.y + v2.y);
}
// This splits the vector (polar or cartesian) into the components along dir and the tangent to that dir
function vectorComponentsForDir(vec,dir){
var v = asPolar(vec); // as polar
var pheta = v.dir - dir;
var Fv = Math.cos(pheta) * v.mag;
var Fa = Math.sin(pheta) * v.mag;
var d1 = dir;
var d2 = dir + PI90;
if(Fv < 0){
d1 += PI;
Fv = -Fv;
}
if(Fa < 0){
d2 += PI;
Fa = -Fa;
}
return {
along : polar(Fv,d1),
tangent : polar(Fa,d2)
};
}
function doCollision(pointDetails, wallIndex){
var vv = asPolar(pointDetails.velocity); // Cartesian V make sure the velocity is in cartesian form
var va = asPolar(pointDetails.velocityA); // Angular V make sure the velocity is in cartesian form
var vvc = vectorComponentsForDir(vv, WALL_NORMS[wallIndex])
var vac = vectorComponentsForDir(va, WALL_NORMS[wallIndex])
vvc.along.mag *= 1.18; // Elastic collision requiers that the two equal forces from the wall
vac.along.mag *= 1.18; // against the box and the box against the wall be summed.
// As the wall can not move the result is that the force is twice
// the force the box applies to the wall (Yes and currently force is in
// velocity form untill the next line)
vvc.along.mag *= box.mass; // convert to force
//vac.along.mag/= pointDetails.radius
vac.along.mag *= box.mass
vvc.along.dir += PI; // force is in the oppisite direction so turn it 180
vac.along.dir += PI; // force is in the oppisite direction so turn it 180
// split the force into components based on the wall normal. One along the norm the
// other along the wall
vvc.tangent.mag *= 0.18; // add friction along the wall
vac.tangent.mag *= 0.18;
vvc.tangent.mag *= box.mass //
vac.tangent.mag *= box.mass
vvc.tangent.dir += PI; // force is in the oppisite direction so turn it 180
vac.tangent.dir += PI; // force is in the oppisite direction so turn it 180
// apply the force out from the wall
box.applyForce(vvc.along, pointDetails.pos)
// apply the force along the wall
box.applyForce(vvc.tangent, pointDetails.pos)
// apply the force out from the wall
box.applyForce(vac.along, pointDetails.pos)
// apply the force along the wall
box.applyForce(vac.tangent, pointDetails.pos)
//addTempVec(pointDetails.pos, vvc.tangent, "red", LIFE, 10)
//addTempVec(pointDetails.pos, vac.tangent, "red", LIFE, 10)
}
function applyForce(force, loc){ // force is a vector, loc is a coordinate
validatePolar(force); // make sure the force is a valid polar
// addTempVec(loc, force,"White", LIFE, SCALE_FORCE) // show the force
var l = asCart(loc); // make sure the location is in cartesian form
var toCenter = asPolar(vector(this.x - l.x, this.y - l.y));
var pheta = toCenter.dir - force.dir;
var Fv = Math.cos(pheta) * force.mag;
var Fa = Math.sin(pheta) * force.mag;
var accel = asPolar(toCenter); // copy the direction to center
accel.mag = Fv / this.mass; // now use F = m * a in the form a = F/m
var deltaV = asCart(accel); // convert it to cartesian
this.dx += deltaV.x // update the box delta V
this.dy += deltaV.y
var accelA = Fa / (toCenter.mag * this.mass); // for the angular component get the rotation
// acceleration
this.dr += accelA;// now add that to the box delta r
}
// make a box
ctx.globalAlpha = 1;
var lx,ly;
function update(){
// clearLog();
ctx.setTransform(1, 0, 0, 1, 0, 0);
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.setTransform(1, 0, 0, 1, 0, 0);
ctx.lineWidth = 1;
ctx.strokeStyle = "black";
ctx.fillStyle = "#888";
ctx.fillRect(INSET, INSET, canvas.width - INSET * 2, canvas.height - INSET * 2);
ctx.strokeRect(INSET, INSET, canvas.width - INSET * 2, canvas.height - INSET * 2);
ctx.lineWidth = 2;
ctx.strokeStyle = "black";
box.update();
box.draw();
if(mouse.buttonRaw & 1){
var force = asPolar(vector(mouse.x - lx, mouse.y - ly));
force.mag *= box.mass * 0.1;
box.applyForce(force,vector(mouse.x, mouse.y))
addTempVec(vector(mouse.x, mouse.y), asPolar(vector(mouse.x - lx, mouse.y - ly)), "Cyan", LIFE, 5);
}
lx = mouse.x;
ly = mouse.y;
for(i = 0; i < 4; i++){
var p = box.getPoint(i);
// only do one collision per frame or we will end up adding energy
if(p.pos.x < INSET){
box.x += (INSET) - p.pos.x;
doCollision(p,3)
}else
if( p.pos.x > canvas.width-INSET){
box.x += (canvas.width - INSET) - p.pos.x;
doCollision(p,1)
}else
if(p.pos.y < INSET){
box.y += (INSET) -p.pos.y;
doCollision(p,0)
}else
if( p.pos.y > canvas.height-INSET){
box.y += (canvas.height - INSET) -p.pos.y;
doCollision(p,2)
}
drawVec(p.pos,p.velocity,"blue")
}
drawTempVecs();
ctx.globalAlpha = 1;
drawText(box.getDesc(),canvas.width/2,FONT_SIZE,FONT,FONT_SIZE,"black");
drawText("Click drag to apply force to box",canvas.width/2,FONT_SIZE +17,FONT,14,"black");
requestAnimationFrame(update)
}
update();

Rotating Images & Pixel Collision Detection

I've got this game in this plunker.
When the swords are not rotating, it all works fine (you can check by uncommenting lines 221 and commenting out 222-223). When they are rotating like in the plunker above, the collision doesn't work well.
I guess that's because the "getImageData" remembers the old images, but I gather it's an expensive thing to recalculate over and over again.
Is there a better way to rotate my images and make this work? Or do I have to recalculate their pixel map?
Code of the culprit:
for (var i = 0; i < monsters.length; i++) {
var monster = monsters[i];
if (monster.ready) {
if (imageCompletelyOutsideCanvas(monster, monster.monsterImage)) {
monster.remove = true;
}
//else {
//ctx.drawImage(monster.monsterImage, monster.x, monster.y);
drawRotatedImage(monster.monsterImage, monster.x, monster.y, monster);
monster.rotateCounter += 0.05;
//}
}
}

Geometric solution
To do this via a quicker geometry solution.
The simplest solution is a line segment with circle intersection algorithm.
Line segment.
A line has a start and end described in a variety of ways. In this case we will use the start and end coordinates.
var line = {
x1 : ?,
y1 : ?,
x2 : ?,
y2 : ?,
}
Circle
The circle is described by its location and radius
var circle = {
x : ?,
y : ?,
r : ?,
}
Circle line segment Intersect
The following describes how I test for the circle line segment collision. I don't know if there is a better way (most likely there is) but this has served me well and is reliable with the caveat that line segments must have length and circles must have area. If you can not guarantee this then you must add checks in the code to ensure you don't get divide by zeros.
Thus to test if a line intercepts the circle we first find out how far the closest point on the line (Note a line is infinite in size while a line segment has a length, start and end)
// a quick convertion of vars to make it easier to read.
var x1 = line.x1;
var y1 = line.y1;
var x2 = line.x2;
var y2 = line.y2;
var cx = circle.x;
var cy = circle.y;
var r = circle.r;
The result of the test, will be true if there is a collision.
var result; // the result of the test
Convert the line to a vector.
var vx = x2 - x1; // convert line to vector
var vy = y2 - y1;
var d2 = (vx * vx + vy * vy); // get the length squared
Get the unit distance from the circle of the near point on the line. The unit distance is a number from 0, to 1 (inclusive) and represents the distance along the vector of a point. if the value is less than 0 then the point is before the vector, if greater then 1 the point is past the end.
I know this by memory and forget the concept. Its the dot product of the line vector and the vector from the start of the line segment to the circle center divided by the line vectors length squared.
// dot product of two vectors is v1.x * v2.x + v1.y * v2.y over v1 length squared
u = ((cx - x1) * vx + (cy - y1) * vy) / d2;
Now use the unit position to get the actual coordinate of the point on the line closest to the circle by adding to the line segment start position the line vector times the unit distance.
// get the closest point
var xx = x1 + vx * u;
var yy = y1 + vy * u;
Now we have a point on the line, we calculate the distance from the circle using pythagoras square root of the sum of the two sides squared.
// get the distance from the circle center
var d = Math.hypot(xx - cx, yy - cy);
Now if the line (not line segment) intersects the circle the distance will be equal or less than the circle radius. Otherwise the is no intercept.
if(d > r){ //is the distance greater than the radius
result = false; // no intercept
} else { // else we need some more calculations
To determine if the line segment has intercepted the circle we need to find the two points on the circle's circumference that the line has crossed. We have the radius and the distance the circle is from the line. As the distance from the line is always at right angles we have a right triangle with the hypot being the radius and one side being the distance found.
Work out the missing length of the triangle. UPDATE see improved version of the code from here at bottom of answer under "update" it uses unit lengths rather than normalise the line vector.
// ld for line distance is the square root of the hyp subtract side squared
var ld = Math.sqrt(r * r - d * d);
Now add that distance to the point we found on the line xx, yy to do that normalise the line vector (makes the line vector one unit long) by dividing the line vector by its length, and then to multiply it by the distance found above
var len = Math.sqrt(d2); // get the line vector length
var nx = (vx / len) * ld;
var ny = (vy / len) * ld;
Some people may see that I could have used the Unit length and skipped a few calculations. Yes but I can be bothered rewriting the demo so will leave it as is
Now to get the to intercept points by adding and subtracting the new vector to the point on the line that is closest to the circle
ix1 = xx + nx; // the point furthest alone the line
iy1 = xx + ny;
ix2 = xx - nx; // the point in the other direction
iy2 = xx - ny;
Now that we have these two points we can work out if they are in the line segment but calculating the unit distance they are on the original line vector, using the dot product divide the squared distance.
var u1 = ((ix1 - x1) * vx + (iy1 - y1) * vy) / d2;
var u2 = ((ix2 - x1) * vx + (iy1 - y1) * vy) / d2;
Now some simple tests to see if the unit postion of these points are on the line segment
if(u1 < 0){ // is the forward intercept befor the line segment start
result = false; // no intercept
}else
if(u2 > 1){ // is the rear intercept after the line end
result = false; // no intercept
} else {
// though the line segment may not have intercepted the circle
// circumference if we have got to here it must meet the conditions
// of touching some part of the circle.
result = true;
}
}
Demo
As always here is a demo showing the logic in action. The circle is centered on the mouse. There are a few test lines that will go red if the circle touches them. It will also show the point where the circle circumference does cross the line. The point will be red if in the line segment or green if outside. These points can be use to add effects or what not
I am lazy today so this is straight from my library. Note I will post the improved math when I get a chance.
Update
I have improved the algorithm by using unit length to calculate the circle circumference intersects, eliminating a lot of code. I have added it to the demo as well.
From the Point where the distance from the line is less than the circle radius
// get the unit distance to the intercepts
var ld = Math.sqrt(r * r - d * d) / Math.sqrt(d2);
// get that points unit distance along the line
var u1 = u + ld;
var u2 = u - ld;
if(u1 < 0){ // is the forward intercept befor the line
result = false; // no intercept
}else
if(u2 > 1){ // is the backward intercept past the end of the line
result = false; // no intercept
}else{
result = true;
}
}
var demo = function(){
// the function described in the answer with extra stuff for the demo
// at the bottom you will find the function being used to test circle intercepts.
/** GeomDependancies.js begin **/
// for speeding up calculations.
// usage may vary from descriptions. See function for any special usage notes
var data = {
x:0, // coordinate
y:0,
x1:0, // 2nd coordinate if needed
y1:0,
u:0, // unit length
i:0, // index
d:0, // distance
d2:0, // distance squared
l:0, // length
nx:0, // normal vector
ny:0,
result:false, // boolean result
}
// make sure hypot is suported
if(typeof Math.hypot !== "function"){
Math.hypot = function(x, y){ return Math.sqrt(x * x + y * y);};
}
/** GeomDependancies.js end **/
/** LineSegCircleIntercept.js begin **/
// use data properties
// result // intercept bool for intercept
// x, y // forward intercept point on line **
// x1, y1 // backward intercept point on line
// u // unit distance of intercept mid point
// d2 // line seg length squared
// d // distance of closest point on line from circle
// i // bit 0 on for forward intercept on segment
// // bit 1 on for backward intercept
// ** x = null id intercept points dont exist
var lineSegCircleIntercept = function(ret, x1, y1, x2, y2, cx, cy, r){
var vx, vy, u, u1, u2, d, ld, len, xx, yy;
vx = x2 - x1; // convert line to vector
vy = y2 - y1;
ret.d2 = (vx * vx + vy * vy);
// get the unit distance of the near point on the line
ret.u = u = ((cx - x1) * vx + (cy - y1) * vy) / ret.d2;
xx = x1 + vx * u; // get the closest point
yy = y1 + vy * u;
// get the distance from the circle center
ret.d = d = Math.hypot(xx - cx, yy - cy);
if(d <= r){ // line is inside circle
// get the distance to the two intercept points
ld = Math.sqrt(r * r - d * d) / Math.sqrt(ret.d2);
// get that points unit distance along the line
u1 = u + ld;
if(u1 < 0){ // is the forward intercept befor the line
ret.result = false; // no intercept
return ret;
}
u2 = u - ld;
if(u2 > 1){ // is the backward intercept past the end of the line
ret.result = false; // no intercept
return ret;
}
ret.i = 0;
if(u1 <= 1){
ret.i += 1;
// get the forward point line intercepts the circle
ret.x = x1 + vx * u1;
ret.y = y1 + vy * u1;
}else{
ret.x = x2;
ret.y = y2;
}
if(u2 >= 0){
ret.x1 = x1 + vx * u2;
ret.y1 = y1 + vy * u2;
ret.i += 2;
}else{
ret.x1 = x1;
ret.y1 = y1;
}
// tough the points of intercept may not be on the line seg
// the closest point to the must be on the line segment
ret.result = true;
return ret;
}
ret.x = null; // flag that no intercept found at all;
ret.result = false; // no intercept
return ret;
}
/** LineSegCircleIntercept.js end **/
// mouse and canvas functions for this demo.
/** fullScreenCanvas.js begin **/
var canvas = (function(){
var canvas = document.getElementById("canv");
if(canvas !== null){
document.body.removeChild(canvas);
}
// creates a blank image with 2d context
canvas = document.createElement("canvas");
canvas.id = "canv";
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
canvas.style.position = "absolute";
canvas.style.top = "0px";
canvas.style.left = "0px";
canvas.style.zIndex = 1000;
canvas.ctx = canvas.getContext("2d");
document.body.appendChild(canvas);
return canvas;
})();
var ctx = canvas.ctx;
/** fullScreenCanvas.js end **/
/** MouseFull.js begin **/
var canvasMouseCallBack = undefined; // if needed
var mouse = (function(){
var mouse = {
x : 0, y : 0, w : 0, alt : false, shift : false, ctrl : false,
interfaceId : 0, buttonLastRaw : 0, buttonRaw : 0,
over : false, // mouse is over the element
bm : [1, 2, 4, 6, 5, 3], // masks for setting and clearing button raw bits;
getInterfaceId : function () { return this.interfaceId++; }, // For UI functions
startMouse:undefined,
};
function mouseMove(e) {
var t = e.type, m = mouse;
m.x = e.offsetX; m.y = e.offsetY;
if (m.x === undefined) { m.x = e.clientX; m.y = e.clientY; }
m.alt = e.altKey;m.shift = e.shiftKey;m.ctrl = e.ctrlKey;
if (t === "mousedown") { m.buttonRaw |= m.bm[e.which-1];
} else if (t === "mouseup") { m.buttonRaw &= m.bm[e.which + 2];
} else if (t === "mouseout") { m.buttonRaw = 0; m.over = false;
} else if (t === "mouseover") { m.over = true;
} else if (t === "mousewheel") { m.w = e.wheelDelta;
} else if (t === "DOMMouseScroll") { m.w = -e.detail;}
if (canvasMouseCallBack) { canvasMouseCallBack(m.x, m.y); }
e.preventDefault();
}
function startMouse(element){
if(element === undefined){
element = document;
}
"mousemove,mousedown,mouseup,mouseout,mouseover,mousewheel,DOMMouseScroll".split(",").forEach(
function(n){element.addEventListener(n, mouseMove);});
element.addEventListener("contextmenu", function (e) {e.preventDefault();}, false);
}
mouse.mouseStart = startMouse;
return mouse;
})();
if(typeof canvas === "undefined"){
mouse.mouseStart(canvas);
}else{
mouse.mouseStart();
}
/** MouseFull.js end **/
// helper function
function drawCircle(ctx,x,y,r,col,col1,lWidth){
if(col1){
ctx.lineWidth = lWidth;
ctx.strokeStyle = col1;
}
if(col){
ctx.fillStyle = col;
}
ctx.beginPath();
ctx.arc( x, y, r, 0, Math.PI*2);
if(col){
ctx.fill();
}
if(col1){
ctx.stroke();
}
}
// helper function
function drawLine(ctx,x1,y1,x2,y2,col,lWidth){
ctx.lineWidth = lWidth;
ctx.strokeStyle = col;
ctx.beginPath();
ctx.moveTo(x1,y1);
ctx.lineTo(x2,y2);
ctx.stroke();
}
var h = canvas.height;
var w = canvas.width;
var unit = Math.ceil(Math.sqrt(Math.hypot(w, h)) / 32);
const U80 = unit * 80;
const U60 = unit * 60;
const U40 = unit * 40;
const U10 = unit * 10;
var lines = [
{x1 : U80, y1 : U80, x2 : w /2, y2 : h - U80},
{x1 : w - U80, y1 : U80, x2 : w /2, y2 : h - U80},
{x1 : w / 2 - U10, y1 : h / 2 - U40, x2 : w /2, y2 : h/2 + U10 * 2},
{x1 : w / 2 + U10, y1 : h / 2 - U40, x2 : w /2, y2 : h/2 + U10 * 2},
];
function update(){
var i, l;
ctx.clearRect(0, 0, w, h);
drawCircle(ctx, mouse.x, mouse.y, U60, undefined, "black", unit * 3);
drawCircle(ctx, mouse.x, mouse.y, U60, undefined, "yellow", unit * 2);
for(i = 0; i < lines.length; i ++){
l = lines[i]
drawLine(ctx, l.x1, l.y1, l.x2, l.y2, "black" , unit * 3)
drawLine(ctx, l.x1, l.y1, l.x2, l.y2, "yellow" , unit * 2)
// test the lineSegment circle
data = lineSegCircleIntercept(data, l.x1, l.y1, l.x2, l.y2, mouse.x, mouse.y, U60);
// if there is a result display the result
if(data.result){
drawLine(ctx, l.x1, l.y1, l.x2, l.y2, "red" , unit * 2)
if((data.i & 1) === 1){
drawCircle(ctx, data.x, data.y, unit * 4, "white", "red", unit );
}else{
drawCircle(ctx, data.x, data.y, unit * 2, "white", "green", unit );
}
if((data.i & 2) === 2){
drawCircle(ctx, data.x1, data.y1, unit * 4, "white", "red", unit );
}else{
drawCircle(ctx, data.x1, data.y1, unit * 2, "white", "green", unit );
}
}
}
requestAnimationFrame(update);
}
update();
}
// resize if needed by just starting again
window.addEventListener("resize",demo);
// start the demo
demo();

... and here's how to find the sword blade lines when the sword is moved & rotated
Start by finding the vertices of the original sword blade and saving them in an array.
var pts=[{x:28,y:42},{x:69,y:3},{x:83,y:1},{x:83,y:19},{x:42,y:57}];
When the sword rotates, each blade vertex point will rotate around the rotation point. In your case the rotation point is the center of the image.
Gray rect is the rectangular border of the image
Blue dot is one sword vertex (at the tip of the blade)
Green dot is at the center of the image (== the rotation point)
Green line is the distance from center-image to vertex
Blue circle is the path the blade tip will follow as it rotates 360 degrees
The green line will change its angle depending on the image's rotation.
You can calculate the position of the blade tip at any angle of rotation like this:
// [cx,cy] = the image centerpoint (== the rotation point)
// [vx,vy] = the coordinate position of the blade tip
// Calculate the distance and the angle between the 2 points
var dx=vx-cx;
var dy=vy-cy;
var distance=Math.sqrt(dx*dx+dy*dy);
var originalAngle=Math.atan2(dy,dx);
// rotationAngle = the angle the image has been rotated expressed in radians
var rotatedX = cx + distance * Math.cos(originalAngle + rotationAngle);
var rotatedY = cy + distance * Math.sin(originalAngle + rotationAngle);
Here's example code and a Demo that tracks blade vertices while being moved and rotated:
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var cw=canvas.width;
var ch=canvas.height;
function reOffset(){
var BB=canvas.getBoundingClientRect();
offsetX=BB.left;
offsetY=BB.top;
}
var offsetX,offsetY;
reOffset();
window.onscroll=function(e){ reOffset(); }
window.onresize=function(e){ reOffset(); }
var isDown=false;
var startX,startY;
var sword={
img:null,
rx:0,
ry:0,
angle:0,
pts:[{x:28,y:42},{x:69,y:3},{x:83,y:1},{x:83,y:19},{x:42,y:57}],
// precalculated properties -- for efficiency
radii:[],
angles:[],
halfWidth:0,
halfHeight:0,
//
initImg:function(img){
var PI2=Math.PI*2;
this.img=img;
this.halfWidth=img.width/2;
this.halfHeight=img.height/2;
for(var i=0;i<this.pts.length;i++){
var dx=this.halfWidth-this.pts[i].x;
var dy=this.halfHeight-this.pts[i].y;
this.radii[i]=Math.sqrt(dx*dx+dy*dy);
this.angles[i]=((Math.atan2(dy,dx)+PI2)%PI2)-Math.PI;
}
},
// draw sword with translation & rotation
draw:function(){
var img=this.img;
var rx=this.rx;
var ry=this.ry;
var angle=this.angle;
ctx.translate(rx,ry);
ctx.rotate(angle);
ctx.drawImage(img,-this.halfWidth,-this.halfHeight);
ctx.rotate(-angle);
ctx.translate(-rx,-ry);
},
// recalc this.pts after translation & rotation
calcTrxPts:function(){
var trxPts=[];
for(var i=0;i<this.pts.length;i++){
var r=this.radii[i];
var ptangle=this.angles[i]+this.angle;
trxPts[i]={
x:this.rx+r*Math.cos(ptangle),
y:this.ry+r*Math.sin(ptangle)
};
}
return(trxPts);
},
}
// load image & initialize sword object & draw scene
var img=new Image();
img.onload=function(){
// set initial sword properties
sword.initImg(img);
sword.rx=150;
sword.ry=75;
sword.angle=0; //(Math.PI/8);
// draw scene
drawAll();
// listen for mouse events
$("#canvas").mousedown(function(e){handleMouseDown(e);});
$("#canvas").mousemove(function(e){handleMouseMove(e);});
$("#canvas").mouseup(function(e){handleMouseUpOut(e);});
$("#canvas").mouseout(function(e){handleMouseUpOut(e);});
// listen for mousewheel events
$("#canvas").on('DOMMouseScroll mousewheel',function(e){
e.preventDefault();
e.stopPropagation();
var e=e || window.event; // old IE support
sign=((e.originalEvent.wheelDelta||e.originalEvent.detail*-1)>0)?1:-1;
sword.angle+=Math.PI/45*sign;
drawAll();
});
}
img.src = "data:image/png;base64,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";
/////////////////////
// helper functions
/////////////////////
function drawAll(){
ctx.clearRect(0,0,cw,ch);
sword.draw();
drawHitArea();
}
function drawHitArea(){
// lines
var trxPts=sword.calcTrxPts();
ctx.beginPath();
ctx.moveTo(trxPts[0].x,trxPts[0].y);
for(var i=1;i<trxPts.length;i++){
ctx.lineTo(trxPts[i].x,trxPts[i].y);
}
ctx.closePath();
ctx.strokeStyle='red';
ctx.stroke();
// dots
for(var i=0;i<trxPts.length;i++){
ctx.beginPath();
ctx.arc(trxPts[i].x,trxPts[i].y,3,0,Math.PI*2);
ctx.closePath();
ctx.fillStyle='blue';
ctx.fill();
}
}
function getClosestPointOnLineSegment(line,x,y) {
//
lerp=function(a,b,x){ return(a+x*(b-a)); };
var dx=line.x1-line.x0;
var dy=line.y1-line.y0;
var t=((x-line.x0)*dx+(y-line.y0)*dy)/(dx*dx+dy*dy);
var lineX=lerp(line.x0, line.x1, t);
var lineY=lerp(line.y0, line.y1, t);
return({x:lineX,y:lineY,isOnSegment:(t>=0 && t<=1)});
};
function handleMouseDown(e){
// tell the browser we're handling this event
e.preventDefault();
e.stopPropagation();
startX=parseInt(e.clientX-offsetX);
startY=parseInt(e.clientY-offsetY);
// Put your mousedown stuff here
isDown=true;
}
function handleMouseUpOut(e){
// tell the browser we're handling this event
e.preventDefault();
e.stopPropagation();
// clear the isDragging flag
isDown=false;
}
function handleMouseMove(e){
if(!isDown){return;}
// tell the browser we're handling this event
e.preventDefault();
e.stopPropagation();
// calc distance moved since last drag
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
var dx=mouseX-startX;
var dy=mouseY-startY;
startX=mouseX;
startY=mouseY;
// drag the sword to new position
sword.rx+=dx;
sword.ry+=dy;
drawAll();
}
body{ background-color: ivory; }
#canvas{border:1px solid red; }
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<h6>Drag sword and<br>Rotate sword using mousewheel inside canvas<br>Red "collision" lines follow swords translation & rotation.</h6>
<h5></h5>
<canvas id="canvas" width=300 height=300></canvas>

Adding perspective to fake 3D animation

I'm working on a canvas-based animation, and I'm trying to get a 3D effect in a 2D canvas.
So far, things are going well! I've got my "orbiting line of triangles" working very well:
var c = document.createElement('canvas');
c.width = c.height = 100;
document.body.appendChild(c);
var ctx = c.getContext("2d");
function Triangles() {
this.rotation = {
x: Math.random()*Math.PI*2,
y: Math.random()*Math.PI*2,
z: Math.random()*Math.PI*2
};
/* Uncomment this for testing perspective...
this.rotation = {
x: Math.PI/2,
y: 0,
z: 0
};
*/
}
Triangles.prototype.draw = function(t) {
this.rotation.z += t/1000;
var i, points;
for( i=0; i<15; i++) {
points = [
this.computeRotation(Math.cos(0.25*i),-Math.sin(0.25*i),0),
this.computeRotation(Math.cos(0.25*(i+1)),-Math.sin(0.25*(i+1)),-0.1),
this.computeRotation(Math.cos(0.25*(i+1)),-Math.sin(0.25*(i+1)),0.1)
];
ctx.fillStyle = "black";
ctx.beginPath();
ctx.moveTo(50+40*points[0][0],50+40*points[0][1]);
ctx.lineTo(50+40*points[1][0],50+40*points[1][1]);
ctx.lineTo(50+40*points[2][0],50+40*points[2][1]);
ctx.closePath();
ctx.fill();
}
};
Triangles.prototype.computeRotation = function(x,y,z) {
var rz, ry, rx;
rz = [
Math.cos(this.rotation.z) * x - Math.sin(this.rotation.z) * y,
Math.sin(this.rotation.z) * x + Math.cos(this.rotation.z) * y,
z
];
ry = [
Math.cos(this.rotation.y) * rz[0] + Math.sin(this.rotation.y) * rz[2],
rz[1],
-Math.sin(this.rotation.y) * rz[0] + Math.cos(this.rotation.y) * rz[2]
];
rx = [
ry[0],
Math.cos(this.rotation.x) * ry[1] - Math.sin(this.rotation.x) * ry[2],
Math.sin(this.rotation.x) * ry[1] + Math.cos(this.rotation.x) * ry[2]
];
return rx;
};
var tri = new Triangles();
requestAnimationFrame(function(start) {
function step(t) {
var delta = t-start;
ctx.clearRect(0,0,100,100)
tri.draw(delta);
start = t;
requestAnimationFrame(step);
}
step(start);
});
As you can see it's using rotation matrices for calculating the position of the points after their rotation, and I'm using this to draw the triangles using the output x and y coordinates.
I want to take this a step further by using the z coordinate and adding perspective to this animation, which will make the triangles slightly bigger when in the foreground, and smaller when in the background. However, I'm not sure how to go about doing this.
I guess this is more of a maths question than a programming one, sorry about that!

Define a focal length to control the amount of perspective. The greater the value the less the amount of perspective. Then
var fl = 200; // focal length;
var px = 100; // point in 3D space
var py = 200;
var pz = 500;
Then to get the screen X,Y
var sx = (px * fl) / pz;
var sy = (py * fl) / pz;
The resulting point is relative to the center of the veiw so you need to center it to the canvas.
sx += canvas.width/2;
sy += canvas.height/2;
That is a point.
It assumes that the point being viewed is in front of the view and further than the focal length from the focal point.

I've managed to figure out a basic solution, but I'm sure there's better ones, so if you have a more complete answer feel free to add it! But for now...
Since the coordinate system is already based around the origin with the viewpoint directly on the Z axis looking at the (x,y) plane, it's actually sufficient to just multiply the (x,y) coordinates by a value proportional to z. For example, x * (z+2)/2 will do just fine in this case
There's bound to be a more proper, general solution though!

Rotating canvas about axis problems

I am using canvas 3d to draw a 3d graph in which i can plot points such as (1,5,4), (-8,6,-2) etc.So i am able to draw in all positive and negative x,y and z axis.I also have rotation effect by using arrow keys.
Instructions for rotation:
The z-axis extends out from the center of the screen.
To rotate about the x-axis, press the up/down arrow keys.
To rotate about the y-axis, press the left/right arrow keys.
To rotate about the z-axis, press the ctrl+left/ctrl+down arrow keys.
I can plot the point by specifying points in the text field i provided.
Now the problem is that for example if i plot(5,5,2) it will plot properly.But if i rotate x axis first and then y axis then point will be plotted properly. The problem comes if i rotate y-axis first and then x-axis.the point will be wrongly plotted.
Easy method to find the problem i encountered:
This can be easily find out if you go on plotting the same point repeatedly.The point should be plotted above the same point so that only single point is visible.But in my case the same point( for ex(5,5,2) is drawn at different place in canvas while rotating.This problem only comes if i rotate y-axis first and then x-axis or if i rotate z axis first and then y-axis. So what is the mistake i have done in coding.I am new to this canvas 3d and java script.So please help.
<html>
<head>
<script src="http://code.jquery.com/jquery-latest.min.js"></script>
<title>Canvas Surface Rotation</title>
<style>
body {
text-align: center;
}
canvas {
border: 1px solid black;
}
</style>
<script>
var p1;
var p2;
var p3;
var p4;
var p5;
var p6;
var xangle=0;
var yangle=0;
var zangle=0;
var constants = {
canvasWidth: 600, // In pixels.
canvasHeight: 600, // In pixels.
leftArrow: 37,
upArrow: 38,
rightArrow: 39,
downArrow: 40,
xMin: -10, // These four max/min values define a square on the xy-plane that the surface will be plotted over.
xMax: 10,
yMin: -10,
yMax: 10,
xDelta: 0.06, // Make smaller for more surface points.
yDelta: 0.06, // Make smaller for more surface points.
colorMap: ["#000080"], // There are eleven possible "vertical" color values for the surface, based on the last row of http://www.cs.siena.edu/~lederman/truck/AdvanceDesignTrucks/html_color_chart.gif
pointWidth: 2, // The size of a rendered surface point (i.e., rectangle width and height) in pixels.
dTheta: 0.05, // The angle delta, in radians, by which to rotate the surface per key press.
surfaceScale: 24 // An empirically derived constant that makes the surface a good size for the given canvas size.
};
// These are constants too but I've removed them from the above constants literal to ease typing and improve clarity.
var X = 0;
var Y = 1;
var Z = 2;
// -----------------------------------------------------------------------------------------------------
var controlKeyPressed = false; // Shared between processKeyDown() and processKeyUp().
var surface = new Surface(); // A set of points (in vector format) representing the surface.
// -----------------------------------------------------------------------------------------------------
function point(x, y, z)
/*
Given a (x, y, z) surface point, returns the 3 x 1 vector form of the point.
*/
{
return [x, y, z]; // Return a 3 x 1 vector representing a traditional (x, y, z) surface point. This vector form eases matrix multiplication.
}
// -----------------------------------------------------------------------------------------------------
function Surface()
/*
A surface is a list of (x, y, z) points, in 3 x 1 vector format. This is a constructor function.
*/
{
this.points = [];
// An array of surface points in vector format. That is, each element of this array is a 3 x 1 array, as in [ [x1, y1, z1], [x2, y2, z2], [x3, y3, z3], ... ]
}
// -----------------------------------------------------------------------------------------------------
Surface.prototype.equation = function(x, y)
/*
Given the point (x, y), returns the associated z-coordinate based on the provided surface equation, of the form z = f(x, y).
*/
{
var d = Math.sqrt(x*x + y*y); // The distance d of the xy-point from the z-axis.
return 4*(Math.sin(d) / d); // Return the z-coordinate for the point (x, y, z).
}
// -----------------------------------------------------------------------------------------------------
Surface.prototype.generate = function()
/*
Creates a list of (x, y, z) points (in 3 x 1 vector format) representing the surface.
*/
{
var i = 0;
for (var x = constants.xMin; x <= constants.xMax; x += constants.xDelta)
{
for (var y = constants.yMin; y <= constants.yMax; y += constants.yDelta)
{
this.points[i] = point(x, y, this.equation(x, y)); // Store a surface point (in vector format) into the list of surface points.
++i;
}
}
}
// -----------------------------------------------------------------------------------------------------
Surface.prototype.color = function()
/*
The color of a surface point is a function of its z-coordinate height.
*/
{
var z; // The z-coordinate for a given surface point (x, y, z).
this.zMin = this.zMax = this.points[0][Z]; // A starting value. Note that zMin and zMax are custom properties that could possibly be useful if this code is extended later.
for (var i = 0; i < this.points.length; i++)
{
z = this.points[i][Z];
if (z < this.zMin) { this.zMin = z; }
if (z > this.zMax) { this.zMax = z; }
}
var zDelta = Math.abs(this.zMax - this.zMin) / constants.colorMap.length;
for (var i = 0; i < this.points.length; i++)
{
this.points[i].color = constants.colorMap[ Math.floor( (this.points[i][Z]-this.zMin)/zDelta ) ];
}
/* Note that the prior FOR loop is functionally equivalent to the follow (much less elegant) loop:
for (var i = 0; i < this.points.length; i++)
{
if (this.points[i][Z] <= this.zMin + zDelta) {this.points[i].color = "#060";}
else if (this.points[i][Z] <= this.zMin + 2*zDelta) {this.points[i].color = "#090";}
else if (this.points[i][Z] <= this.zMin + 3*zDelta) {this.points[i].color = "#0C0";}
else if (this.points[i][Z] <= this.zMin + 4*zDelta) {this.points[i].color = "#0F0";}
else if (this.points[i][Z] <= this.zMin + 5*zDelta) {this.points[i].color = "#9F0";}
else if (this.points[i][Z] <= this.zMin + 6*zDelta) {this.points[i].color = "#9C0";}
else if (this.points[i][Z] <= this.zMin + 7*zDelta) {this.points[i].color = "#990";}
else if (this.points[i][Z] <= this.zMin + 8*zDelta) {this.points[i].color = "#960";}
else if (this.points[i][Z] <= this.zMin + 9*zDelta) {this.points[i].color = "#930";}
else if (this.points[i][Z] <= this.zMin + 10*zDelta) {this.points[i].color = "#900";}
else {this.points[i].color = "#C00";}
}
*/
}
// -----------------------------------------------------------------------------------------------------
function update(){
document.querySelector("#xa").innerHTML = xangle;
document.querySelector("#ya").innerHTML = yangle;
document.querySelector("#za").innerHTML = zangle;
}
function appendCanvasElement()
/*
Creates and then appends the "myCanvas" canvas element to the DOM.
*/
{
var canvasElement = document.createElement('canvas');
canvasElement.width = constants.canvasWidth;
canvasElement.height = constants.canvasHeight;
canvasElement.id = "myCanvas";
canvasElement.getContext('2d').translate(constants.canvasWidth/2, constants.canvasHeight/2); // Translate the surface's origin to the center of the canvas.
document.body.appendChild(canvasElement); // Make the canvas element a child of the body element.
}
//------------------------------------------------------------------------------------------------------
Surface.prototype.sortByZIndex = function(A, B)
{
return A[Z] - B[Z]; // Determines if point A is behind, in front of, or at the same level as point B (with respect to the z-axis).
}
// -----------------------------------------------------------------------------------------------------
Surface.prototype.draw = function()
{
var myCanvas = document.getElementById("myCanvas"); // Required for Firefox.
var ctx = myCanvas.getContext("2d");
var res;
var xm;
// this.points = surface.points.sort(surface.sortByZIndex); // Sort the set of points based on relative z-axis position. If the points are visibly small, you can sort of get away with removing this step.
for (var i = 0; i < this.points.length; i++)
{
ctx.fillStyle = this.points[i].color;
ctx.fillRect(this.points[i][X] * constants.surfaceScale, this.points[i][Y] * constants.surfaceScale, constants.pointWidth, constants.pointWidth);
}
var c=document.getElementById("myCanvas");
var ctx=c.getContext("2d");
ctx.font="12px Arial";
ctx.fillStyle = "#000000";
ctx.fillText("X",this.points[p1][X] * constants.surfaceScale, this.points[p1][Y] * constants.surfaceScale);
var c=document.getElementById("myCanvas");
var ctx1=c.getContext("2d");
ctx1.font="12px Arial";
ctx1.fillText("Y",this.points[p2][X] * constants.surfaceScale, this.points[p2][Y] * constants.surfaceScale);
var c=document.getElementById("myCanvas");
var ctx1=c.getContext("2d");
ctx1.font="12px Arial";
ctx1.fillText("Z",this.points[p3][X] * constants.surfaceScale, this.points[p3][Y] * constants.surfaceScale);
var c=document.getElementById("myCanvas");
var ctx1=c.getContext("2d");
ctx1.font="12px Arial";
ctx1.fillText("-Y",this.points[p4][X] * constants.surfaceScale, this.points[p4][Y] * constants.surfaceScale);
var c=document.getElementById("myCanvas");
var ctx1=c.getContext("2d");
ctx1.font="12px Arial";
ctx1.fillText("-Z",this.points[p5][X] * constants.surfaceScale, this.points[p5][Y] * constants.surfaceScale);
var c=document.getElementById("myCanvas");
var ctx1=c.getContext("2d");
ctx1.font="12px Arial";
ctx1.fillText("-X",this.points[p6][X] * constants.surfaceScale, this.points[p6][Y] * constants.surfaceScale);
}
// -----------------------------------------------------------------------------------------------------
Surface.prototype.multi = function(R)
/*
Assumes that R is a 3 x 3 matrix and that this.points (i.e., P) is a 3 x n matrix. This method performs P = R * P.
*/
{
var Px = 0, Py = 0, Pz = 0; // Variables to hold temporary results.
var P = this.points; // P is a pointer to the set of surface points (i.e., the set of 3 x 1 vectors).
var sum; // The sum for each row/column matrix product.
for (var V = 0; V < P.length; V++) // For all 3 x 1 vectors in the point list.
{
Px = P[V][X], Py = P[V][Y], Pz = P[V][Z];
for (var Rrow = 0; Rrow < 3; Rrow++) // For each row in the R matrix.
{
sum = (R[Rrow][X] * Px) + (R[Rrow][Y] * Py) + (R[Rrow][Z] * Pz);
P[V][Rrow] = sum;
}
}
}
Surface.prototype.multipt = function(R)
/*
Assumes that R is a 3 x 3 matrix and that this.points (i.e., P) is a 3 x n matrix. This method performs P = R * P.
*/
{
var Px = 0, Py = 0, Pz = 0; // Variables to hold temporary results.
var P = this.points; // P is a pointer to the set of surface points (i.e., the set of 3 x 1 vectors).
var sum; // The sum for each row/column matrix product.
for (var V = P.length-1; V < P.length; V++) // For all 3 x 1 vectors in the point list.
{
Px = P[V][X], Py = P[V][Y], Pz = P[V][Z];
for (var Rrow = 0; Rrow < 3; Rrow++) // For each row in the R matrix.
{
sum = (R[Rrow][X] * Px) + (R[Rrow][Y] * Py) + (R[Rrow][Z] * Pz);
P[V][Rrow] = sum;
}
}
}
// -----------------------------------------------------------------------------------------------------
Surface.prototype.erase = function()
{
var myCanvas = document.getElementById("myCanvas"); // Required for Firefox.
var ctx = myCanvas.getContext("2d");
ctx.clearRect(-constants.canvasWidth/2, -constants.canvasHeight/2, myCanvas.width, myCanvas.height);
}
// -----------------------------------------------------------------------------------------------------
Surface.prototype.xRotate = function(sign)
/*
Assumes "sign" is either 1 or -1, which is used to rotate the surface "clockwise" or "counterclockwise".
*/
{
var Rx = [ [0, 0, 0],
[0, 0, 0],
[0, 0, 0] ]; // Create an initialized 3 x 3 rotation matrix.
Rx[0][0] = 1;
Rx[0][1] = 0; // Redundant but helps with clarity.
Rx[0][2] = 0;
Rx[1][0] = 0;
Rx[1][1] = Math.cos( sign*constants.dTheta );
Rx[1][2] = -Math.sin( sign*constants.dTheta );
Rx[2][0] = 0;
Rx[2][1] = Math.sin( sign*constants.dTheta );
Rx[2][2] = Math.cos( sign*constants.dTheta );
this.multi(Rx); // If P is the set of surface points, then this method performs the matrix multiplcation: Rx * P
this.erase(); // Note that one could use two canvases to speed things up, which also eliminates the need to erase.
this.draw();
}
// -----------------------------------------------------------------------------------------------------
Surface.prototype.yRotate = function(sign)
/*
Assumes "sign" is either 1 or -1, which is used to rotate the surface "clockwise" or "counterclockwise".
*/
{
var Ry = [ [0, 0, 0],
[0, 0, 0],
[0, 0, 0] ]; // Create an initialized 3 x 3 rotation matrix.
Ry[0][0] = Math.cos( sign*constants.dTheta );
Ry[0][1] = 0; // Redundant but helps with clarity.
Ry[0][2] = Math.sin( sign*constants.dTheta );
Ry[1][0] = 0;
Ry[1][1] = 1;
Ry[1][2] = 0;
Ry[2][0] = -Math.sin( sign*constants.dTheta );
Ry[2][1] = 0;
Ry[2][2] = Math.cos( sign*constants.dTheta );
this.multi(Ry); // If P is the set of surface points, then this method performs the matrix multiplcation: Rx * P
this.erase(); // Note that one could use two canvases to speed things up, which also eliminates the need to erase.
this.draw();
}
// -----------------------------------------------------------------------------------------------------
Surface.prototype.zRotate = function(sign)
/*
Assumes "sign" is either 1 or -1, which is used to rotate the surface "clockwise" or "counterclockwise".
*/
{
var Rz = [ [0, 0, 0],
[0, 0, 0],
[0, 0, 0] ]; // Create an initialized 3 x 3 rotation matrix.
Rz[0][0] = Math.cos( sign*constants.dTheta );
Rz[0][1] = -Math.sin( sign*constants.dTheta );
Rz[0][2] = 0; // Redundant but helps with clarity.
Rz[1][0] = Math.sin( sign*constants.dTheta );
Rz[1][1] = Math.cos( sign*constants.dTheta );
Rz[1][2] = 0;
Rz[2][0] = 0
Rz[2][1] = 0;
Rz[2][2] = 1;
this.multi(Rz); // If P is the set of surface points, then this method performs the matrix multiplcation: Rx * P
this.erase(); // Note that one could use two canvases to speed things up, which also eliminates the need to erase.
this.draw();
}
Surface.prototype.xRotatept = function()
{
var Rx = [ [0, 0, 0],
[0, 0, 0],
[0, 0, 0] ];
Rx[0][0] = 1;
Rx[0][1] = 0;
Rx[0][2] = 0;
Rx[1][0] = 0;
Rx[1][1] = Math.cos(xangle);
Rx[1][2] = -Math.sin(xangle);
Rx[2][0] = 0;
Rx[2][1] = Math.sin(xangle);
Rx[2][2] = Math.cos(xangle);
this.multipt(Rx);
this.erase();
this.draw();
}
Surface.prototype.yRotatept = function()
{
var Ry = [ [0, 0, 0],
[0, 0, 0],
[0, 0, 0] ];
Ry[0][0] = Math.cos(yangle);
Ry[0][1] = 0;
Ry[0][2] = Math.sin(yangle);
Ry[1][0] = 0;
Ry[1][1] = 1;
Ry[1][2] = 0;
Ry[2][0] = -Math.sin(yangle);
Ry[2][1] = 0;
Ry[2][2] = Math.cos(yangle);
this.multipt(Ry);
this.erase();
this.draw();
}
Surface.prototype.zRotatept = function()
{
var Rz = [ [0, 0, 0],
[0, 0, 0],
[0, 0, 0] ];
Rz[0][0] = Math.cos(zangle);
Rz[0][1] = -Math.sin(zangle);
Rz[0][2] = 0;
Rz[1][0] = Math.sin(zangle);
Rz[1][1] = Math.cos(zangle);
Rz[1][2] = 0;
Rz[2][0] = 0
Rz[2][1] = 0;
Rz[2][2] = 1;
this.multipt(Rz);
this.erase();
this.draw();
}
// -----------------------------------------------------------------------------------------------------
function processKeyDown(evt)
{
if (evt.ctrlKey)
{
switch (evt.keyCode)
{
case constants.upArrow:
// No operation other than preventing the default behavior of the arrow key.
evt.preventDefault(); // This prevents the default behavior of the arrow keys, which is to scroll the browser window when scroll bars are present. The user can still scroll the window with the mouse.
break;
case constants.downArrow:
// No operation other than preventing the default behavior of the arrow key.
evt.preventDefault();
break;
case constants.leftArrow:
// console.log("ctrl+leftArrow");
zangle=zangle-0.05;
update();
if(zangle<=-2*Math.PI)
{
zangle=0;
}
surface.zRotate(-1); // The sign determines if the surface rotates "clockwise" or "counterclockwise".
evt.preventDefault();
break;
case constants.rightArrow:
// console.log("ctrl+rightArrow");
zangle=zangle+0.05;
update();
if(zangle>=2*Math.PI)
{
zangle=0;
}
surface.zRotate(1);
evt.preventDefault();
break;
}
return; // When the control key is pressed, only the left and right arrows have meaning, no need to process any other key strokes (i.e., bail now).
}
// Assert: The control key is not pressed.
switch (evt.keyCode)
{
case constants.upArrow:
// console.log("upArrow");
xangle=xangle+0.05;
update();
if(xangle>=2*Math.PI)
{
xangle=0;
}
surface.xRotate(1);
evt.preventDefault();
break;
case constants.downArrow:
// console.log("downArrow");
xangle=xangle-0.05;
update();
if(xangle<=-2*Math.PI)
{
xangle=0;
}
surface.xRotate(-1);
evt.preventDefault();
break;
case constants.leftArrow:
// console.log("leftArrow");
yangle=yangle-0.05;
update();
if(yangle<=-2*Math.PI)
{
yangle=0;
}
surface.yRotate(-1);
evt.preventDefault();
break;
case constants.rightArrow:
// console.log("rightArrow");
yangle=yangle+0.05;
update();
if(yangle>=2*Math.PI)
{
yangle=0;
}
surface.yRotate(1);
evt.preventDefault();
break;
}
}
// -----------------------------------------------------------------------------------------------------
Surface.prototype.plot = function(x, y, z)
/*
add the point (x, y, z) (in 3 x 1 vector format) to the surface.
*/
{
this.points.push(point(x, y, z)); // Store a surface point
var x=0;
for (var x = constants.xMin; x <= constants.xMax; x += constants.xDelta)
{
this.points.push(point(x, 0, 0));
}
p6=1;
p1=this.points.length-1;
p4=this.points.length;
/*var y=-0.2
for (var x = constants.xMax+1; x <= constants.xMax+2; x += constants.xDelta)
{
this.points.push(point(x, y, 0));
y=y+0.002
}*/
/*for (var x = constants.xMax+1; x <= constants.xMax+2; x += constants.xDelta)
{
this.points.push(point(11, 0, 0))
}*/
for (var x = constants.xMin; x <= constants.xMax; x += constants.yDelta)
{
this.points.push(point(0, x, 0));
}
p2=this.points.length-1;
p5=this.points.length;
for (var x = constants.xMin; x <= constants.xMax; x += constants.yDelta)
{
this.points.push(point(0,0,x));
}
p3=this.points.length-1;
}
Surface.prototype.plot1 = function(x, y, z)
/*
add the point (x, y, z) (in 3 x 1 vector format) to the surface.
*/
{
this.points.push(point(x, y, z)); // Store a surface point
surface.xRotatept();
surface.yRotatept();
surface.zRotatept();
this.draw();
}
function onloadInit()
{
appendCanvasElement(); // Create and append the canvas element to the DOM.
surface.draw(); // Draw the surface on the canvas.
document.addEventListener('keydown', processKeyDown, false); // Used to detect if the control key has been pressed.
}
// -----------------------------------------------------------------------------------------------------
//surface.generate(); // Creates the set of points reprsenting the surface. Must be called before color().
surface.plot(0,0,0);
surface.color(); // Based on the min and max z-coordinate values, chooses colors for each point based on the point's z-ccordinate value (i.e., height).
window.addEventListener('load', onloadInit, false); // Perform processing that must occur after the page has fully loaded.
</script>
</head>
<body>
<table align="center">
<tr><td>
<h5 style="color:#606">Enter the value of (X,Y,Z)</h5>
<input type="text" value="5" class="num-input" width="50" size="2" id="x-input">
<input type="text" value="5" class="num-input" width="50" size="2" id="y-input">
<input type="text" value="2" class="num-input" width="50" size="2" id="z-input">
<input type="button" value="Plot Point" onClick="surface.plot1(document.getElementById('x-input').value,document.getElementById('y-input').value,document.getElementById('z-input').value); ">
</td></tr></table>
<table align="center"> <tr><td>
<span id="xa">0</span>deg<br>
<span id="ya">0</span>deg<br>
<span id="za">0</span>deg</td></tr></table>
</body>
</html>

The final output of rotations along multiple axis can vary depending on the order that you rotate the axis'. What you need to do is keep track of the total rotation along each axis (as three numbers, not using matrices). And each time you update a rotation value, apply all three total rotations to an identity matrix in the correct order (try x,y,z). Always use the same order. Then use this to transform your coordinates.

here is my opinion:
JAVASCRIPT
var canvas = document.getElementById("myCanvas");
var ctx2 = canvas.getContext("2d");
ctx2.fillStyle='#333';
ctx2.fillRect(50,50,100,100);
var ctx = canvas.getContext("2d");
ctx.fillStyle='red';
var deg = Math.PI/180;
ctx.save();
ctx.translate(100, 100);
ctx.rotate(45 * deg);
ctx.fillRect(-50,-50,100,100);
ctx.restore();
ctx2 is the old position and ctx is the new position of the shape. You have to translate the shape with the same x,y coordinates according to where you want position your shape. Then you have to enter values to ctx.fillRect(x,y,w,h);keep x and y as the -ve values (half of height and width to keep it on the diagonal to the canvas otherwise change to manipulate it). and h, w as your desired values.
DEMO