Related
Please check out this code :
(function() {
var cnv = document.getElementById('canvas');
if (cnv.getContext) {
var ctx = cnv.getContext('2d');
} else {
alert('God Damn it ...');
}
function initialize() {
window.addEventListener('resize', resizeCanvas, false);
resizeCanvas();
}
function draw() {
for (var i = 0; i < 25; i++) {
width = Math.random() * cnv.width;
height = Math.random() * cnv.height;
ctx.beginPath();
ctx.arc(width, height, 15, 0, Math.PI * 2);
ctx.strokeStyle = '#E1E1E1';
ctx.lineWidth = 1;
ctx.stroke();
}
}
function resizeCanvas() {
cnv.width = window.innerWidth;
cnv.height = window.innerHeight;
draw();
}
initialize();
})();
I have created 25 Circle shape with random position and I want to create an animation that scales up or down in a interval time. I know about setInterval but how should I call my shape to do something on it?
The first thing you will want to do is to have a place to store the position of your circles, since they are all going to be the same radius we can just store the x and y position. For that we can create a Circle function ("class") and have an array of circles:
var circles = []; // Array to store our circles
var minRadius = 1; // The smallest radius we can hit
var maxRadius = 100; // The largest radius we can hit
var currentRadius = 15;// The current radius of all our circles
var scaleBy = 1; // How the radius changes
var cnv = document.getElementById('canvas');
// ...
function initialize() {
window.addEventListener('resize', resizeCanvas, false);
resizeCanvas();
// Populating the array of circles to use when drawing
for (var i = 0; i < 25; i++) { // Make sure to do this after re-sizing the canvas
width = Math.random() * cnv.width;
height = Math.random() * cnv.height;
circles.push(new Circle(width, height));
}
}
// ...
function Circle(x, y){
this.x = x;
this.y = y;
}
Circle.prototype.draw = function(){
ctx.beginPath();
ctx.arc(this.x, this.y, currentRadius, 0, Math.PI * 2);
ctx.strokeStyle = '#E1E1E1';
ctx.lineWidth = 5;
ctx.stroke();
}
Now that you have some circles when you call draw you can iterate through the array and call circle.draw() for each circle element in your array:
function draw() {
// Clear the screen and draw the circles in our array
ctx.clearRect(0,0, cnv.width, cnv.height);
for (var i = 0; i < circles.length; i++) {
circles[i].draw();
}
}
One note is you will want to use ctx.clearRect(0,0, cnv.width, cnv.height) to clear the screen before drawing.
Finally you can now use setInterval to change the currentRadius (*While there is nothing wrong with setInterval I'd recommend using window.requestAnimationFrame for animation as it's a bit more smooth and efficient method). Then when you call draw it will draw the circles with the new value of currentRadius. In this example I'm going to have it start at 15. Then increase by 1 until it hits maxRadius, then we can flip the sign of scaleBy to start decreasing the radius to make them smaller. Finally when it his our minRadius you can flip the sign of scaleBy again to make it start scaling up again:
var timer = setInterval( function(){
// If we hit our min or max start scaling in the other direction
if(currentRadius > maxRadius || currentRadius < minRadius){
scaleBy *= -1;
}
currentRadius += scaleBy;
draw();
}, 50);
Below is a code snippet of the complete program:
(function() {
var circles = [];
var minRadius = 1;
var maxRadius = 100;
var currentRadius = 15;
var scaleBy = 1;
var cnv = document.getElementById('canvas');
if (cnv.getContext) {
var ctx = cnv.getContext('2d');
} else {
alert('God Damn it ...');
}
function initialize() {
window.addEventListener('resize', resizeCanvas, false);
resizeCanvas();
for (var i = 0; i < 25; i++) {
width = Math.random() * cnv.width;
height = Math.random() * cnv.height;
circles.push(new Circle(width, height));
}
}
function draw() {
ctx.clearRect(0,0, cnv.width, cnv.height);
for (var i = 0; i < circles.length; i++) {
circles[i].draw();
}
}
function resizeCanvas() {
cnv.width = window.innerWidth;
cnv.height = window.innerHeight;
}
function Circle(x, y){
this.x = x;
this.y = y;
}
Circle.prototype.draw = function(){
ctx.beginPath();
ctx.arc(this.x, this.y, currentRadius, 0, Math.PI * 2);
ctx.strokeStyle = '#E1E1E1';
ctx.lineWidth = 5;
ctx.stroke();
}
initialize();
var timer = setInterval( function(){
if(currentRadius > maxRadius || currentRadius < minRadius){
scaleBy *= -1;
}
currentRadius += scaleBy;
draw();
}, 50);
})();
<canvas id="canvas"></canvas>
I'm attempting to draw the rotating line in this canvas animation with trailing opacity but it's not working. I've seen this effect with rectangles and arcs but never with a line, so I'm not sure what I need to add.
function radians(degrees) {
return degrees * (Math.PI / 180);
}
var timer = 0;
function sonar() {
var canvas = document.getElementById('sonar');
if (canvas) {
var ctx = canvas.getContext('2d');
var cx = innerWidth / 2,
cy = innerHeight / 2;
canvas.width = innerWidth;
canvas.height = innerHeight;
//ctx.clearRect(0, 0, innerWidth, innerHeight);
ctx.fillStyle = 'rgba(255, 255, 255, 0.5)';
ctx.fillRect(0, 0, innerWidth, innerHeight);
var radii = [cy, cy - 30, innerHeight / 3.33, innerHeight / 6.67];
for (var a = 0; a < 4; a++) {
ctx.beginPath();
ctx.arc(cx, cy, radii[a], radians(0), radians(360), false);
ctx.strokeStyle = 'limegreen';
ctx.stroke();
ctx.closePath();
}
// draw grid lines
for (var i = 0; i < 12; i++) {
var x = cx + cy * Math.cos(radians(i * 30));
var y = cy + cy * Math.sin(radians(i * 30));
ctx.beginPath();
ctx.moveTo(cx, cy);
ctx.lineTo(x, y);
ctx.lineCap = 'round';
ctx.strokeStyle = 'rgba(50, 205, 50, 0.45)';
ctx.stroke();
ctx.closePath();
}
if (timer <= 360) {
timer++;
ctx.beginPath();
ctx.fillstyle = 'limegreen';
ctx.moveTo(cx, cy);
ctx.lineTo(cx + cy * Math.cos(radians(timer)), cy + cy * Math.sin(radians(timer)));
ctx.strokeStyle = 'limegreen';
ctx.stroke();
ctx.closePath();
} else {
timer = 0;
}
requestAnimationFrame(sonar);
}
}
sonar();
jsbin example
Here are two ways to do this: with a gradient and by adding translucent lines.
Sidenote, you should try and only redraw what you need to redraw. I separated the canvases and put one on top of the other so that we don't redraw the grid all the time.
function radians(degrees) {
return degrees * (Math.PI / 180);
}
var timer = 0;
function trail() {
var canvas = document.getElementById('trail');
var ctx = canvas.getContext('2d');
ctx.clearRect(0, 0, innerWidth, innerHeight);
var cx = innerWidth / 2,
cy = innerHeight / 2;
canvas.width = innerWidth;
canvas.height = innerHeight;
if (timer <= 360) {
timer++;
ctx.beginPath();
ctx.fillstyle = 'limegreen';
ctx.moveTo(cx, cy);
ctx.arc(cx,cy,cy,radians(timer-30),radians(timer));
ctx.lineTo(cx + cy * Math.cos(radians(timer)), cy + cy * Math.sin(radians(timer)));
var gradient = ctx.createLinearGradient(
cx+cy*Math.cos(radians(timer)), cy+cy*Math.sin(radians(timer)),
cx+cy*0.9*Math.cos(radians(timer-30)), cy+cy*0.9*Math.sin(radians(timer-30)));
gradient.addColorStop(0,'limegreen');
gradient.addColorStop(1,'transparent');
ctx.strokeStyle='transparent';
ctx.fillStyle = gradient;
ctx.fill();
ctx.beginPath();
var fade = 10;
for(var i =0;i<fade;i++)
{
ctx.moveTo(cx, cy);
ctx.lineTo(cx+cy*Math.cos(radians(180+timer-i*1.3)),cy+cy*Math.sin(radians(180+timer-i*1.3)));
ctx.strokeStyle ="rgba(50,205,50,0.1)";
ctx.lineWidth=5;
ctx.closePath();
ctx.stroke();
}
} else {
timer = 0;
}
requestAnimationFrame(trail);
}
function sonar() {
var canvas = document.getElementById('sonar');
if (canvas) {
var ctx = canvas.getContext('2d');
var cx = innerWidth / 2,
cy = innerHeight / 2;
canvas.width = innerWidth;
canvas.height = innerHeight;
//ctx.clearRect(0, 0, innerWidth, innerHeight);
var radii = [cy, cy - 30, innerHeight / 3.33, innerHeight / 6.67];
for (var a = 0; a < 4; a++) {
ctx.beginPath();
ctx.arc(cx, cy, radii[a], radians(0), radians(360), false);
ctx.strokeStyle = 'limegreen';
ctx.stroke();
ctx.closePath();
}
// draw grid lines
for (var i = 0; i < 12; i++) {
var x = cx + cy * Math.cos(radians(i * 30));
var y = cy + cy * Math.sin(radians(i * 30));
ctx.beginPath();
ctx.moveTo(cx, cy);
ctx.lineTo(x, y);
ctx.lineCap = 'round';
ctx.strokeStyle = 'rgba(50, 205, 50, 0.45)';
ctx.stroke();
ctx.closePath();
}
}
}
sonar();
trail();
canvas{
position: absolute;
}
<canvas id=sonar></canvas>
<canvas id=trail></canvas>
The problem is that to get this effect, you need to draw a triangle with a gradient along an arc, and you can't do that in a canvas. Gradients must be linear or radial.
The other option is to have an inner loop run each time you want to draw the sweeper, and go backwards from your sweeper line, drawing with slightly less opacity each time. But lets say you want your sweep to cover 15 degrees--obviously, if you have a 100% opacity line at d and a 5% opacity line at d - 15, that doesn't do the trick. So start filling in more lines, and more lines...you will have to draw so many lines to make it seem filled your performance would probably suffer.
My suggestion--you shouldn't have to redraw that on every frame. I would just make a PNG that looks like you want it to, and then place it and just rotate it around the center on each frame. No need to redraw it all the time then. That will be much faster than drawing a bunch of lines.
Canvas stack trails.
Below is a quick demo of how to use a stack of canvases to create a trailing effect.
You have a normal on screen canvas (this FX will not effect it) and then a stack of canvases for the trail FX. Each frame you move to the next canvas in the stack, first slightly clearing it then drawing to it what you want to trail. Then you render that canvas and the one just above it to the canvas.
A point to keep in mind is that the trails can also have a hugh range of FX, like blurring (just render each frame stack on itself slightly offset each time you render to it), zoom in and out trails. Trails on top or trails under. You can change the trail distance and much more.
It is overkill but over kill is fun.
The slider above the demo controls the trail length. Also the code need babel because I dont have time to write it for ES5.
Top slider is trail amount.One under that is trail distance. Trail dist does not transition well. Sorry about that.
//==============================================================================
// helper function
function $(query,q1){
if(q1 !== undefined){
if(typeof query === "string"){
var e = document.createElement(query);
if(typeof q1 !== "string"){
for(var i in q1){
e[i] = q1[i];
}
}else{
e.id = q1;
}
return e;
}
return [...query.querySelectorAll(q1)];
}
return [...document.querySelectorAll(query)];
}
function $$(element,e1){
if(e1 !== undefined){
if(typeof element === "string"){
$(element)[0].appendChild(e1);
return e1;
}
element.appendChild(e1);
return e1;
}
document.body.appendChild(element);
return element;
}
function $E(element,types,listener){
if(typeof types === "string"){
types = types.split(",");
}
element = $(element)[0];
types.forEach(t=>{
element.addEventListener(t,listener)
});
return element;
}
function R(I){
if(I === undefined){
return Math.random();
}
return Math.floor(Math.random()*I);
}
//==============================================================================
//==============================================================================
// answer code
// canvas size
const size = 512;
const trailDist = 10; // There is this many canvases so be careful
var trailDistCurrent = 10; // distance between trails
var clearAll = false;
// create a range slider for trail fade
$$($("input",{type:"range",width : size, min:0, max:100, step:0.1, value:50, id:"trail-amount",title:"Trail amount"}));
$("#trail-amount")[0].style.width = size + "px";
$E("#trail-amount","change,mousemove",function(e){fadeAmount = Math.pow(this.value / 100,2);});
// create a range slider trail distance
$$($("input",{type:"range",width : size, min:2, max:trailDist , step:1, value:trailDist , id:"trail-dist",title:"Trail seperation"}));
$("#trail-dist")[0].style.width = size + "px";
$E("#trail-dist","change,mousemove", function(e){
if(this.value !== trailDistCurrent){
trailDistCurrent= this.value;
clearAll = true;
}
});
$$($("br","")) // put canvas under the slider
// Main canvas
var canvas;
$$(canvas = $("canvas",{width:size,height:size})); // Not jquery. Just creates a canvas
// and adds canvas to the document
var ctx = canvas.getContext("2d");
// Trailing canvas
var trailCanvases=[];
var i =0; // create trail canvas
while(i++ < trailDist){trailCanvases.push($("canvas",{width:size,height:size}));}
var ctxT = trailCanvases.map(c=>c.getContext("2d")); // get context
var topCanvas = 0;
var fadeAmount = 0.5;
// Draw a shape
function drawShape(ctx,shape){
ctx.lineWidth = shape.width;
ctx.lineJoin = "round";
ctx.strokeStyle = shape.color;
ctx.setTransform(shape.scale,0,0,shape.scale,shape.x,shape.y);
ctx.rotate(shape.rot);
ctx.beginPath();
var i = 0;
ctx.moveTo(shape.shape[i++],shape.shape[i++]);
while(i < shape.shape.length){
ctx.lineTo(shape.shape[i++],shape.shape[i++]);
}
ctx.stroke();
}
// Create some random shapes
var shapes = (function(){
function createRandomShape(){
var s = [];
var len = Math.floor(Math.random()*5 +4)*2;
while(len--){
s[s.length] = (R() + R()) * 20 * (R() < 0.5 ? -1 : 1);
}
return s;
}
var ss = [];
var i = 10;
while(i--){
ss[ss.length] = createRandomShape();
}
ss[ss.length] = [0,0,300,0]; // create single line
return ss;
})();
// Create some random poits to move the shapes
var points = (function(){
function point(){
return {
color : "hsl("+R(360)+",100%,50%)",
shape : shapes[R(shapes.length)],
width : R(4)+1,
x : R(size),
y : R(size),
scaleMax : R()*0.2 + 1,
scale : 1,
s : 0,
rot : R()*Math.PI * 2,
dr : R()*0.2 -0.1,
dx : R()*2 - 1,
dy : R()*2 - 1,
ds : R() *0.02 + 0.01,
}
}
var line = shapes.pop();
var ss = [];
var i = 5;
while(i--){
ss[ss.length] = point();
}
var s = ss.pop();
s.color = "#0F0";
s.x = s.y = size /2;
s.dx = s.dy = s.ds = 0;
s.scaleMax = 0.5;
s.dr = 0.02;
s.shape = line;
s.width = 6;
ss.push(s);
return ss;
})();
var frameCount = 0; // used to do increamental fades for long trails
function update(){
// to fix the trail distance problem when fade is low and distance high
if(clearAll){
ctxT.forEach(c=>{
c.setTransform(1,0,0,1,0,0);
c.clearRect(0,0,size,size);
});
clearAll = false;
}
frameCount += 1;
// get the next canvas that the shapes are drawn to.
topCanvas += 1;
topCanvas %= trailDistCurrent;
var ctxTop = ctxT[topCanvas];
// clear the main canvas
ctx.setTransform(1,0,0,1,0,0); // reset transforms
// Fade the trail canvas
ctxTop.setTransform(1,0,0,1,0,0);
ctx.clearRect(0,0,size,size); // clear main canvas
// slowly blendout trailing layer
if(fadeAmount < 0.1){ // fading much less than this leaves perminant trails
// so at low levels just reduce how often the fade is done
if(((Math.floor(frameCount/trailDistCurrent)+topCanvas) % Math.ceil(1 / (fadeAmount * 10))) === 0 ){
ctxTop.globalAlpha = 0.1;
ctxTop.globalCompositeOperation = "destination-out";
ctxTop.fillRect(0,0,size,size);
}
}else{
ctxTop.globalAlpha = fadeAmount;
ctxTop.globalCompositeOperation = "destination-out";
ctxTop.fillRect(0,0,size,size);
}
ctxTop.globalCompositeOperation = "source-over";
ctxTop.globalAlpha = 1;
// draw shapes
for(var i = 0; i < points.length; i ++){
var p = points[i];
p.x += p.dx; // move the point
p.y += p.dy;
p.rot += p.dr;
p.s += p.ds;
p.dr += Math.sin(p.s) * 0.001;
p.scale = Math.sin(p.s) * p.scaleMax+1;
p.x = ((p.x % size) + size) % size;
p.y = ((p.y % size) + size) % size;
drawShape(ctxTop,p); // draw trailing layer (middle)
}
// draw the trail the most distance from the current position
ctx.drawImage(trailCanvases[(topCanvas + 1)%trailDistCurrent],0,0);
// do it all again.
requestAnimationFrame(update);
}
update();
I want to draw circular balls on an HTML canvas in a pyramid pattern.
Like this:
Fiddle where you can show me the algorithm:
https://jsfiddle.net/ofxmr17c/3/
var canvas = document.getElementById('canvas');
canvas.width = 400;
canvas.height = 400;
var ctx = canvas.getContext('2d');
var balls = [];
var ballsLength = 15;
var Ball = function() {
this.x = 0;
this.y = 0;
this.radius = 10;
};
Ball.prototype.draw = function(x, y) {
this.x = x;
this.y = y;
ctx.fillStyle = '#333';
ctx.beginPath();
ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2, true);
ctx.fill();
ctx.closePath();
};
init();
function init() {
for (var i = 0; i < ballsLength; i++) {
balls.push(new Ball());
}
render();
}
function render() {
for (var i = 1; i <= ballsLength; i++) {
if (i >= 1 && i <= 5) {
balls[i].draw(i * 20 + balls[i].radius, 20 + balls[i].radius);
}
if (i >= 6 && i <= 9) {
balls[i].draw(i * 20 + balls[i].radius, 20 + balls[i].radius * 2);
}
if (i >= 10 && i <= 12) {
balls[i].draw(i * 20 + balls[i].radius, 20 + balls[i].radius * 3);
}
if (i >= 13 && i <= 14) {
balls[i].draw(i * 20 + balls[i].radius, 20 + balls[i].radius * 4);
}
if (i == 15) {
balls[i].draw(i * 20 + balls[i].radius, 20 + balls[i].radius * 5);
}
}
window.requestAnimationFrame(render);
}
canvas {
border: 1px solid #333;
}
<canvas id="canvas"></canvas>
I have Ball class with x, y and radius variables:
var Ball = function() {
this.x = 0;
this.y = 0;
this.radius = 10;
};
Then I have method of the Ball class which draws the balls on the canvas:
Ball.prototype.draw = function(x, y) {
this.x = x;
this.y = y;
ctx.fillStyle = '#333';
ctx.beginPath();
ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2, true);
ctx.fill();
ctx.closePath();
};
I want to create method which will place any number of balls into a pyramid.
The live demo below shows how to pack an arbitrary number of balls into a pyramid using a bit of trigonometry. To change the amount of layers in the pyramid (and thus the number of balls), edit the NUM_ROWS variable.
This is how it looks when it's done:
Live Demo:
var canvas = document.getElementById('canvas');
canvas.width = 400;
canvas.height = 400;
var ctx = canvas.getContext('2d');
var balls = [];
var ballsLength = 15;
var Ball = function() {
this.x = 0;
this.y = 0;
this.radius = 10;
};
Ball.prototype.draw = function(x, y) {
this.x = x;
this.y = y;
ctx.fillStyle = '#333';
ctx.beginPath();
ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2, true);
ctx.fill();
ctx.closePath();
};
init();
function init() {
for (var i = 0; i < ballsLength; i++) {
balls.push(new Ball());
}
render();
}
function render() {
var NUM_ROWS = 5;
for (var i = 1; i <= NUM_ROWS; i++) {
for (var j = 0; j < i; j++) {
balls[i].draw(j * balls[0].radius * 2 + 150 - i * balls[0].radius, -(i * balls[0].radius * 2 * Math.sin(Math.PI / 3)) + 150);
}
}
//window.requestAnimationFrame(render);
}
canvas {
border: 1px solid #333;
}
<canvas id="canvas"></canvas>
JSFiddle Version: https://jsfiddle.net/ofxmr17c/6/
A billiard pyramid like this is always made with some known facts:
Each row always contains one more ball than the previous
It's an equilateral equal angled (sp? in english?) triangle which means next row always starts offset 60°
So we can make a vector (everything else in a billiard game would very much involve vectors so why not! :) ) for the direction of the next row's start point like so:
var deg60 = -60 / 180 * Math.PI; // -60°, up-right direction
var v = {
x: radius * Math.cos(deg60),
y: radius * Math.sin(deg60)
}
Then the algorithm would be (driven by total number of balls):
Start with a max limit of 1 for first row
Plot balls until max limit for row is reached
Then, add one to the max limit
Reset row count
Move position to beginning of last row + vector
Repeat until number of balls is reached
Result:
Example
var ctx = c.getContext("2d"),
radius = 9, // ball radius
deg = -60 / 180 * Math.PI, // direction of row start -60°
balls = 15, // number of balls to draw
drawn = 0, // count balls drawn on current row
rowLen = 1, // max length of current row (first=1)
x = 150, // start point
y = 140,
cx = 150, cy =140, // replicates start point + offsets
v = { // vector
x: radius * 2 * Math.cos(deg),
y: radius * 2 * Math.sin(deg)
},
i;
for(i = 0; i < balls; i++) {
drawBall(cx, cy); // draw ball
cx -= radius * 2; // move diameter of ball to left (in this case)
drawn++; // increase balls on row count
if (drawn === rowLen) { // reached max balls for row?
cx = x + v.x * rowLen; // increase one row
cy = y + v.y * rowLen;
drawn = 0; // reset ball count for row
rowLen++; // increase row limit
}
}
ctx.fillStyle = "#D70000";
ctx.fill();
function drawBall(x, y) {
ctx.moveTo(x + radius, y); ctx.arc(x, y, radius, 0, 6.28);
ctx.closePath();
}
<canvas id=c height=300></canvas>
If you want more flexibility in terms of rotation you can simply swap this line:
cx -= radius * 2;
with a vector perpendicular (calculation not shown) to the first vector so:
cx += pv.x;
cy += pv.y;
I'm trying to find a way to put as much hexagons in a circle as possible. So far the best result I have obtained is by generating hexagons from the center outward in a circular shape.
But I think my calculation to get the maximum hexagon circles is wrong, especially the part where I use the Math.ceil() and Math.Floor functions to round down/up some values.
When using Math.ceil(), hexagons are sometimes overlapping the circle.
When using Math.floor() on the other hand , it sometimes leaves too much space between the last circle of hexagons and the circle's border.
var c_el = document.getElementById("myCanvas");
var ctx = c_el.getContext("2d");
var canvas_width = c_el.clientWidth;
var canvas_height = c_el.clientHeight;
var PI=Math.PI;
var PI2=PI*2;
var hexCircle = {
r: 110, /// radius
pos: {
x: (canvas_width / 2),
y: (canvas_height / 2)
}
};
var hexagon = {
r: 20,
pos:{
x: 0,
y: 0
},
space: 1
};
drawHexCircle( hexCircle, hexagon );
function drawHexCircle(hc, hex ) {
drawCircle(hc);
var hcr = Math.ceil( Math.sqrt(3) * (hc.r / 2) );
var hr = Math.ceil( ( Math.sqrt(3) * (hex.r / 2) ) ) + hexagon.space; // hexRadius
var circles = Math.ceil( ( hcr / hr ) / 2 );
drawHex( hc.pos.x , hc.pos.y, hex.r ); //center hex ///
for (var i = 1; i<=circles; i++) {
for (var j = 0; j<6; j++) {
var currentX = hc.pos.x+Math.cos(j*PI2/6)*hr*2*i;
var currentY = hc.pos.y+Math.sin(j*PI2/6)*hr*2*i;
drawHex( currentX,currentY, hex.r );
for (var k = 1; k<i; k++) {
var newX = currentX + Math.cos((j*PI2/6+PI2/3))*hr*2*k;
var newY = currentY + Math.sin((j*PI2/6+PI2/3))*hr*2*k;
drawHex( newX,newY, hex.r );
}
}
}
}
function drawHex(x, y, r){
ctx.beginPath();
ctx.moveTo(x,y-r);
for (var i = 0; i<=6; i++) {
ctx.lineTo(x+Math.cos((i*PI2/6-PI2/4))*r,y+Math.sin((i*PI2/6-PI2/4))*r);
}
ctx.closePath();
ctx.stroke();
}
function drawCircle( circle ){
ctx.beginPath();
ctx.arc(circle.pos.x, circle.pos.y, circle.r, 0, 2 * Math.PI);
ctx.closePath();
ctx.stroke();
}
<canvas id="myCanvas" width="350" height="350" style="border:1px solid #d3d3d3;">
If all the points on the hexagon are within the circle, the hexagon is within the circle. I don't think there's a simpler way than doing the distance calculation.
I'm not sure how to select the optimal fill point, (but here's a js snippet proving that the middle isn't always it). It's possible that when you say "hexagon circle" you mean hexagon made out of hexagons, in which case the snippet proves nothing :)
I made the hexagon sides 2/11ths the radius of the circle and spaced them by 5% the side length.
var hex = {x:0, y:0, r:10};
var circle = {x:100, y:100, r:100};
var spacing = 1.05;
var SQRT_3 = Math.sqrt(3);
var hexagon_offsets = [
{x: 1/2, y: -SQRT_3 / 2},
{x: 1, y: 0},
{x: 1/2, y: SQRT_3 / 2},
{x: -1/2, y: SQRT_3 / 2},
{x: -1, y: 0},
{x: -1/2, y: -SQRT_3 / 2}
];
var bs = document.body.style;
var ds = document.documentElement.style;
bs.height = bs.width = ds.height = ds.width = "100%";
bs.border = bs.margin = bs.padding = 0;
var c = document.createElement("canvas");
c.style.display = "block";
c.addEventListener("mousemove", follow, false);
document.body.appendChild(c);
var ctx = c.getContext("2d");
window.addEventListener("resize", redraw);
redraw();
function follow(e) {
hex.x = e.clientX;
hex.y = e.clientY;
redraw();
}
function drawCircle() {
ctx.strokeStyle = "black";
ctx.beginPath();
ctx.arc(circle.x, circle.y, circle.r, 0, 2 * Math.PI, true);
ctx.closePath();
ctx.stroke();
}
function is_in_circle(p) {
return Math.pow(p.x - circle.x, 2) + Math.pow(p.y - circle.y, 2) < Math.pow(circle.r, 2);
}
function drawLine(a, b) {
var within = is_in_circle(a) && is_in_circle(b);
ctx.strokeStyle = within ? "green": "red";
ctx.beginPath();
ctx.moveTo(a.x, a.y);
ctx.lineTo(b.x, b.y);
ctx.closePath();
ctx.stroke();
return within;
}
function drawShape(shape) {
var within = true;
for (var i = 0; i < shape.length; i++) {
within = drawLine(shape[i % shape.length], shape[(i + 1) % shape.length]) && within;
}
if (!within) return false;
ctx.fillStyle = "green";
ctx.beginPath();
ctx.moveTo(shape[0].x, shape[0].y);
for (var i = 1; i <= shape.length; i++) {
ctx.lineTo(shape[i % shape.length].x, shape[i % shape.length].y);
}
ctx.closePath();
ctx.fill();
return true;
}
function calculate_hexagon(x, y, r) {
return hexagon_offsets.map(function (offset) {
return {x: x + r * offset.x, y: y + r * offset.y};
})
}
function drawHexGrid() {
var hex_count = 0;
var grid_space = calculate_hexagon(0, 0, hex.r * spacing);
var y = hex.y;
var x = hex.x;
while (y > 0) {
y += grid_space[0].y * 3;
x += grid_space[0].x * 3;
}
while (y < c.height) {
x %= grid_space[1].x * 3;
while (x < c.width) {
var hexagon = calculate_hexagon(x, y, hex.r);
if (drawShape(hexagon)) hex_count++;
x += 3 * grid_space[1].x;
}
y += grid_space[3].y;
x += grid_space[3].x;
x += 2 * grid_space[1].x;
}
return hex_count;
}
function redraw() {
c.width = window.innerWidth;
c.height = window.innerHeight;
circle.x = c.width / 2;
circle.y = c.height / 2;
circle.r = Math.min(circle.x, circle.y) * 0.9;
hex.r = circle.r * (20 / 110);
ctx.clearRect(0, 0, c.width, c.height);
var hex_count = drawHexGrid();
drawCircle();
ctx.fillStyle = "rgb(0, 0, 50)";
ctx.font = "40px serif";
ctx.fillText(hex_count + " hexes within circle", 20, 40);
}
I have this code:
ctx.beginPath();
ctx.moveTo(X1,Y1);
ctx.lineTo(X2,Y2);
ctx.lineTo(X3,Y3);
ctx.lineTo(X4,Y4);
ctx.closePath();
ctx.stroke();
Note:
There are four points (A,B,C,D).
Triangle can be formed if X1 !== X3
An Imaginary line is formed between the points to form a triangle shape
You'll have to choose which shape you will draw, here is an implementation drawing four possible ones :
var ctx = canvas.getContext('2d'),
activePoint,
dragging,
names='ABCD';
pointWidth = 10,
points=[];
function isBetween(p,f){
return (f-pointWidth/2 <= p && p <= f+pointWidth/2);
}
function draw(){
ctx.clearRect(0,0,canvas.width,canvas.height);
if(points.length===4)
drawTriangle();
drawPoints();
}
function drawPoints(){
ctx.strokeStyle="black"
ctx.fillStyle="black"
for(var i=0; i<points.length; i++){
ctx.beginPath();
ctx.arc(points[i].x, points[i].y, pointWidth, 0, 2*Math.PI);
ctx.stroke();
}
ctx.strokeStyle="purple"
ctx.beginPath();
for(var i=0; i<points.length-1; i++){
ctx.moveTo(points[i].x, points[i].y);
ctx.lineTo(points[(i+1)].x, points[(i+1)].y);
ctx.fillText(names[i],points[i].x, points[i].y-pointWidth);
}
ctx.stroke();
ctx.fillText(names[points.length-1],points[points.length-1].x, points[points.length-1].y-pointWidth);
}
function drawTriangle(){
var db = {x1:points[3].x, y1:points[3].y, x2:points[1].x, y2:points[1].y};
var l1 = drawLines(db);
var ca = {x1:points[2].x, y1:points[2].y, x2:points[0].x, y2:points[0].y};
var l2 = drawLines(ca);
var inter = getIntersect(l1, l2);
if(inter){
ctx.fillStyle="rgba(255,0,255,.25)";
ctx.beginPath();
ctx.lineTo(l1.x1, l1.y1);
ctx.lineTo(inter.x, inter.y);
ctx.lineTo(l2.x2, l2.y2);
ctx.closePath();
ctx.fill();
ctx.fillStyle="rgba(0,0,255,.25)";
ctx.beginPath();
ctx.lineTo(l2.x1, l2.y1);
ctx.lineTo(inter.x, inter.y);
ctx.lineTo(l1.x2, l1.y2);
ctx.closePath();
ctx.fill();
ctx.fillStyle="rgba(255,0,0,.25)";
ctx.beginPath();
ctx.lineTo(l1.x1, l1.y1);
ctx.lineTo(inter.x, inter.y);
ctx.lineTo(l2.x1, l2.y1);
ctx.closePath();
ctx.fill();
ctx.fillStyle="rgba(255,255,0,.25)";
ctx.beginPath();
ctx.lineTo(l2.x2, l2.y2);
ctx.lineTo(inter.x, inter.y);
ctx.lineTo(l1.x2, l1.y2);
ctx.closePath();
ctx.fill();
ctx.fillStyle= "red";
ctx.beginPath();
ctx.arc(inter.x, inter.y, pointWidth/3, 0, 2*Math.PI);
ctx.fill();
}
}
function drawLines(pt){
var segLength = Math.sqrt(Math.pow((pt.x1 - pt.x2), 2) + Math.pow((pt.y1 - pt.y2), 2)),
startDist = Math.max(canvas.width,canvas.height)*-2,
endDist = startDist*-1;
var rX1 = pt.x2 + (pt.x2 - pt.x1) / segLength * startDist;
var rY1 = pt.y2 + (pt.y2 - pt.y1) / segLength * startDist;
var rX2 = pt.x2 + (pt.x2 - pt.x1) / segLength * endDist;
var rY2 = pt.y2 + (pt.y2 - pt.y1) / segLength * endDist;
ctx.beginPath();
ctx.strokeStyle="green";
ctx.moveTo(rX1, rY1);
ctx.lineTo(rX2, rY2);
ctx.stroke();
return {x1:rX1, y1:rY1, x2:rX2, y2:rY2};
}
function getIntersect(l1, l2){
den = ((l2.y2 - l2.y1) * (l1.x2 - l1.x1)) - ((l2.x2 - l2.x1) * (l1.y2 - l1.y1));
if (den == 0) {
return false;
}
a = l1.y1 - l2.y1;
b = l1.x1 - l2.x1;
num1 = ((l2.x2 - l2.x1) * a) - ((l2.y2 - l2.y1) * b);
num2 = ((l1.x2 - l1.x1) * a) - ((l1.y2 - l1.y1) * b);
a = num1 / den;
b = num2 / den;
var x = l1.x1 + (a * (l1.x2 - l1.x1));
var y = l1.y1 + (a * (l1.y2 - l1.y1));
return {x:x,y:y};
}
canvas.onmousemove = function(e){
var rect = this.getBoundingClientRect();
var x = e.clientX-rect.left;
var y = e.clientY-rect.top;
if(!dragging){
for(var i=0; i< points.length; i++){
if(isBetween(x, points[i].x) && isBetween(y, points[i].y)){
this.style.cursor = 'pointer';
activePoint = points[i];
return;
}
}
this.style.cursor = 'default';
activePoint = null;
}
else{
activePoint.x=x; activePoint.y=y;
draw();
}
}
canvas.onmousedown = function(e){
if(points.length<4){
var rect = this.getBoundingClientRect();
var x = e.clientX-rect.left;
var y = e.clientY-rect.top;
points.push({x:x, y:y})
draw();
}
if(!activePoint) return;
dragging = true;
}
canvas.onmouseup = function(e){
dragging = false;
}
canvas{border: 1px solid red}
<canvas id="canvas" width="500" height="500"></canvas>
Basically what you need are:
1. Get the Infinity line of lines AC and BD.
2. Get the intersection point of lines AC and BD.(2nd point).
3. After saving the intersection point choose the infinity lines between A,B,C and D depending on your constraint then make an infinity out of it (3rd point).
4. Go back to your line to serve as a point 1