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Fill an Unknown Asymmetric Polygon with Pixel Manipulation (WebImage) in JS

Recently, I have been trying to create code to fill a polygon of any shape with color. I have gotten as far as being able to fill a shape that has lines of only one border size correctly, though I have found myself unable to do anything more than that. The problem is that the code does not know when to consider a line of pixels greater than that which it expects as a vertical or horizontal border of the shape. I am going through each pixel of the shape from left to right and checking if any of the pixels have any form of color by checking if the alpha value is 0 or not. Once it finds a pixel that does have an alpha value of anything other than 0, it moves forward a single pixel and then uses the even/odd technique to determine whether the point is inside part of the polygon or not (it makes an infinite line to the right and determines if the number of collisions with colored lines is odd, and if it is, the point is inside the polygon). In general, we consider a single, lone pixel to count as a single line, and we consider a horizontal line of more than one pixel to be two lines because of how often horizontal lines will be part of a border or not. Take the following scenario:
Here, the red dot is the point (pixel) we begin testing from. If we did not consider that horizontal line in the middle to be two points (as is shown by the red lines and x's), we would only have two points of intersection and therefore would not fill the pixel despite the fact that we most definitely do want to fill that pixel. As stated earlier, however, this brings up another problem with a different scenario:
In this case, if we do count a horizontal line of more than one pixel to be two separate lines, we end up not filling any areas with borders that are thicker than the expected thickness. For your reference, the function to handle this is as follows:
//imgData is essentially a WebImage object (explained more below) and r, g, and b are the color values for the fill color
function fillWithColor(imgData, r, g, b) {
//Boolean determining whether we should color the given pixel(s) or not
var doColor = false;
//Booleans determining whether the last pixel found in the entire image was colored
var blackLast = false;
//Booleans determining whether the last 1 or 2 pixels found after a given pixel were colored
var foundBlackPrev, foundBlackPrev2 = false;
//The number of colored pixels found
var blackCount = 0;
//Loop through the entire canvas
for(var y = 0; y < imgData.height; y += IMG_SCALE) {
for(var x = 0; x < imgData.width; x += IMG_SCALE) {
//Test if given pixel is colored
if(getAlpha(imgData, x, y) != 0) {
//If the last pixel was black, begin coloring
if(!blackLast) {
blackLast = true;
doColor = true;
}
} else {
//If the current pixel is not colored, but the last one was, find all colored lines to the right
if(blackLast){
for(var i = x; i < imgData.width; i += IMG_SCALE) {
//If the pixel is colored...
if(getAlpha(imgData, i, y) != 0) {
//If no colored pixel was found before, add to the count
if(!foundBlackPrev){
blackCount++;
foundBlackPrev = true;
} else {
//Otherwise, at least 2 colored pixels have been found in a row
foundBlackPrev2 = true;
}
} else {
//If two or more colored pixels were found in a row, add to the count
if(foundBlackPrev2) {
blackCount++;
}
//Reset the booleans
foundBlackPrev2 = foundBlackPrev = false;
}
}
}
//If the count is odd, we start coloring
if(blackCount & 1) {
blackCount = 0;
doColor = true;
} else {
//If the last pixel in the entire image was black, we stop coloring
if(blackLast) {
doColor = false;
}
}
//Reset the boolean
blackLast = false;
//If we are to be coloring the pixel, color it
if(doColor) {
//Color the pixel
for(var j = 0; j < IMG_SCALE; j++) {
for(var k = 0; k < IMG_SCALE; k++) {
//This is the same as calling setRed, setGreen, setBlue and setAlpha functions from the WebImage API all at once (parameters in order are WebImage object equivalent, x position of pixel, y position of pixel, red value, green value, blue value, and alpha value)
setRGB(imgData, x + j, y + k, r, g, b, 255);
}
}
}
}
}
}
//Update the image (essentially the same as removing all elements from the given area and calling add on the image)
clearCanvas();
putImageData(imgData, 0, 0, imgData.width, imgData.height);
//Return the modified data
return imgData;
}
Where...
imgData is the collection of all of the pixels in the given area (essentially a WebImage object)
IMG_SCALE is the integer value by which the image has been scaled up (which gives us the scale of the pixels as well). In this example, it is equal to 4 because the image is scaled up to 192x256 (from 48x64). This means that every "pixel" you see in the image is actually comprised of a 4x4 block of identically-colored pixels.
So, what I'm really looking for here is a way to determine whether a given colored pixel that comes after another is part of a horizontal border or if it is just another piece comprising the thickness of a vertical border. In addition, if I have the wrong approach to this problem in general, I would greatly appreciate any suggestions as to how to do this more efficiently. Thank you.

I understand the problem and I think you would do better if you would switch your strategy here. We know the following:
the point of start is inside the shape
the color should be filled for every pixel inside the shape
So, we could always push the neighbors of the current point into a queue to be processed and be careful to avoid processing the same points twice, this way traversing all the useful pixels and including them into the coloring plan. The function below is untested.
function fillColor(pattern, startingPoint, color, boundaryColor) {
let visitQueue = [];
let output = {};
if (startingPoint.x - 1 >= 0) visitQueue.push({startingPoint.x - 1, startingPoint.y});
if (startingPoint.x + 1 < pattern.width) visitQueue.push({startingPoint.x + 1, startingPoint.y});
if (startingPoint.y + 1 < pattern.height) visitQueue.push({startingPoint.x, startingPoint.y + 1});
if (startingPoint.y - 1 >= 0) visitQueue.push({startingPoint.x, startingPoint.y - 1});
let visited = {};
while (visitQueue.length > 0) {
let point = visitQueue[0];
visitQueue.shift();
if ((!visited[point.x]) || (visited[point.x].indexOf(point.y) < 0)) {
if (!visited[point.x]) visited[point.x] = [];
visited[point.x].push(point.y);
if (isBlank(pattern, point)) { //you need to implement isBlank
if (!output[point.x]) output[point.x] = [];
output[point.x].push(point.y);
if (point.x + 1 < pattern.width) visitQueue.push({point.x + 1, point.y});
if (point.x - 1 >= 0) visitQueue.push({point.x - 1, point.y});
if (point.y + 1 < pattern.height) visitQueue.push({point.x, point.y + 1});
if (point.y - 1 >= 0) visitQueue.push({point.x, point.y - 1})
}
}
}
return output;
}

As far as I understood you cannot "consider a horizontal line of more than one pixel to be two lines". I don't think you need to count black pixels the way you do, rather count groups of 1 or more pixels.
I would also tidy the code by avoiding using the "doColor" boolean variable. You could rather move the coloring code to a new function color(x,y) and call it straight away.

const ctx = document.querySelector("canvas").getContext("2d");
//ctx.lineWidth(10);//-as you asked we are setting greater border or line width,BUT "LINEWIDTH" IS NOT WORKING IN INBUILT STACKOVERFLOW SNIPPET USE IT IN A FILE I THINK STACKOVERFLOW IS NOT UP-TO-DATE,IN ANY IDE UNCOMENT THIS
ctx.beginPath();
ctx.moveTo(20, 20);
ctx.lineTo(250, 70);
ctx.lineTo(270, 120);
ctx.lineTo(170, 140);
ctx.lineTo(190, 80);
ctx.lineTo(100, 60);
ctx.lineTo(50, 130);
ctx.lineTo(20, 20);
ctx.stroke();
function getMousePosition(canvas, event) {
let rect = canvas.getBoundingClientRect();
let mx = event.clientX - rect.left;
let my = event.clientY - rect.top;
console.log("Coordinate x: " + mx, "Coordinate y: " + my);
floodFill(ctx, mx, my, [155, 0, 255, 255], 128);
}
let canvasElem = document.querySelector("canvas");
canvasElem.addEventListener("mousedown", function(e) {
getMousePosition(canvasElem, e);
});
function getPixel(imageData, x, y) {
if (x < 0 || y < 0 || x >= imageData.width || y >= imageData.height) {
return [-1, -1, -1, -1]; // impossible color
} else {
const offset = (y * imageData.width + x) * 4;
return imageData.data.slice(offset, offset + 4);
}
}
function setPixel(imageData, x, y, color) {
const offset = (y * imageData.width + x) * 4;
imageData.data[offset + 0] = color[0];
imageData.data[offset + 1] = color[1];
imageData.data[offset + 2] = color[2];
imageData.data[offset + 3] = color[0];
}
function colorsMatch(a, b, rangeSq) {
const dr = a[0] - b[0];
const dg = a[1] - b[1];
const db = a[2] - b[2];
const da = a[3] - b[3];
return dr * dr + dg * dg + db * db + da * da < rangeSq;
}
function floodFill(ctx, x, y, fillColor, range = 1) {
// read the pixels in the canvas
const imageData = ctx.getImageData(0, 0, ctx.canvas.width, ctx.canvas.height);
// flags for if we visited a pixel already
const visited = new Uint8Array(imageData.width, imageData.height);
// get the color we're filling
const targetColor = getPixel(imageData, x, y);
// check we are actually filling a different color
if (!colorsMatch(targetColor, fillColor)) {
const rangeSq = range * range;
const pixelsToCheck = [x, y];
while (pixelsToCheck.length > 0) {
const y = pixelsToCheck.pop();
const x = pixelsToCheck.pop();
const currentColor = getPixel(imageData, x, y);
if (!visited[y * imageData.width + x] &&
colorsMatch(currentColor, targetColor, rangeSq)) {
setPixel(imageData, x, y, fillColor);
visited[y * imageData.width + x] = 1; // mark we were here already
pixelsToCheck.push(x + 1, y);
pixelsToCheck.push(x - 1, y);
pixelsToCheck.push(x, y + 1);
pixelsToCheck.push(x, y - 1);
}
}
// put the data back
ctx.putImageData(imageData, 0, 0);
}
}
<canvas></canvas>
This is based on other answers
note:"LINEWIDTH" IS NOT WORKING IN INBUILT STACKOVERFLOW SNIPPET USE IT IN A FILE I THINK STACKOVERFLOW IS NOT UP-TO-DATE,
But it works well in simple HTML,JS website

polygon weird redrawing by adding & dragging dynamic points (flickering)

I have co-ordinates for the points by taking which I draw a polygon. I can add points dynamically on the edges of the polygon and when I drag any point it should drag only the connected lines. As points can be added later on the edges so the point co-ordinates need to be ordered/sorted and the polygon should be redrawn by taking the ordered/sorted points so that on dragging any point the lines connected to the dragged point only should be dragged/updated. So to order/sort the points I am sorting the co-ordinates(2D-points) clockwise using Graham Scan/ sorting by polar angle.
My sorting code is
I find the center of the polygon like
function findCenter(points) {
let x = 0,
y = 0,
i,
len = points.length;
for (i = 0; i < len; i++) {
x += Number(points[i][0]);
y += Number(points[i][1]);
}
return { x: x / len, y: y / len }; // return average position
}
Then I sort the points by finding angles of each point from the center like
function findAngle(points) {
const center = findCenter(points);
// find angle
points.forEach((point) => {
point.angle = Math.atan2(point[1] - center.y, point[0] - center.x);
});
}
//arrVertexes is the array of points
arrVertexes.sort(function (a, b) {
return a.angle >= b.angle ? 1 : -1;
});
But the problem I am facing is if I drag any point more towards opposite side and add a new point on the edges afterward and drag the newly added point the sorting of co-ordinates is not ordered exactly because of which there is a flickering while dragging.
Here is a pictorial view of the problem I am facing for quick understanding.
Initially my svg looks like
After this I add a point and dragged like
Then I added one more point like
once I drag the added point towards down, it redraws the polygon something like (is not it weird ?)
Actually It should be like
NOTE: I really don't know what logic should I apply to get the desire functionality. Seeking help from the community leads.
Demo App
So I am looking for a solution that won't give me weird redrawing of the lines. Only the connected lines to the dragged point should be dragged.
EDIT
I came up with MUCH BETTER solution. The only problem with this approach is, When I try to add a new point on left-vertical line and If I try to move it, that newly added point moves to top-horizontal line
Updated-Demo

I've fixed this bug with left line. Take a look: codepen.
I changed getClosestPointOnLines function (actually refactored a little):
as I understood, the result here is to get i - the index for the new point in array, so I moved the algorithm to new function getI
I changed getI to use not only n (current index), but just 2 any indexes: n1 and n2: const getI = (n1, n2) => {
So all your aXys[n] is now a1 and aXys[n - 1] is now a2.
the result of getI is return i; - this is what we want from this function
I added new function-helper updateI. It calls getI and check if there any positive result.
const updateI = (n1, n2) => {
const newI = getI(n1, n2);
if (newI !== undefined) {
i = newI;
return true;
}
};
So your loop over points is now:
for (let n = 1; n < aXys.length; n++) {
updateI(n, n - 1);
}
But we need to check "left" line separately (because it connects begin and end of the array):
if (updateI(aXys.length - 1, 0)) i = aXys.length;
Sorry, but I disabled part of your code. I did not check where do you use it:
if (i < aXys.length) {
let dx = aXys[i - 1][0] - aXys[i][0];
let dy = aXys[i - 1][1] - aXys[i][1];
x = aXys[i - 1][0] - dx * fTo;
y = aXys[i - 1][1] - dy * fTo;
}
So the final version of getClosestPointOnLines now looks like this:
function getClosestPointOnLines(pXy, aXys) {
var minDist;
var fTo;
var fFrom;
var x;
var y;
var i;
var dist;
if (aXys.length > 1) {
const getI = (n1, n2) => {
let i;
const a1 = aXys[n1];
const a2 = aXys[n2];
if (a1[0] != a2[0]) {
let a = (a1[1] - a2[1]) / (a1[0] - a2[0]);
let b = a1[1] - a * a1[0];
dist = Math.abs(a * pXy[0] + b - pXy[1]) / Math.sqrt(a * a + 1);
} else dist = Math.abs(pXy[0] - a1[0]);
// length^2 of line segment
let rl2 = Math.pow(a1[1] - a2[1], 2) + Math.pow(a1[0] - a2[0], 2);
// distance^2 of pt to end line segment
let ln2 = Math.pow(a1[1] - pXy[1], 2) + Math.pow(a1[0] - pXy[0], 2);
// distance^2 of pt to begin line segment
let lnm12 = Math.pow(a2[1] - pXy[1], 2) + Math.pow(a2[0] - pXy[0], 2);
// minimum distance^2 of pt to infinite line
let dist2 = Math.pow(dist, 2);
// calculated length^2 of line segment
let calcrl2 = ln2 - dist2 + lnm12 - dist2;
// redefine minimum distance to line segment (not infinite line) if necessary
if (calcrl2 > rl2) dist = Math.sqrt(Math.min(ln2, lnm12));
if (minDist == null || minDist > dist) {
if (calcrl2 > rl2) {
if (lnm12 < ln2) {
fTo = 0; //nearer to previous point
fFrom = 1;
} else {
fFrom = 0; //nearer to current point
fTo = 1;
}
} else {
// perpendicular from point intersects line segment
fTo = Math.sqrt(lnm12 - dist2) / Math.sqrt(rl2);
fFrom = Math.sqrt(ln2 - dist2) / Math.sqrt(rl2);
}
minDist = dist;
i = n1;
}
return i;
};
const updateI = (n1, n2) => {
const newI = getI(n1, n2);
if (newI !== undefined) {
i = newI;
return true;
}
};
for (let n = 1; n < aXys.length; n++) {
updateI(n, n - 1);
}
if (updateI(aXys.length - 1, 0)) i = aXys.length;
if (i < aXys.length) {
let dx = aXys[i - 1][0] - aXys[i][0];
let dy = aXys[i - 1][1] - aXys[i][1];
x = aXys[i - 1][0] - dx * fTo;
y = aXys[i - 1][1] - dy * fTo;
}
}
console.log(aXys[i - 1]);
return { x: x, y: y, i: i, fTo: fTo, fFrom: fFrom };
}
Working example on codepen.

You should not allow any point to be added that is not close to a line.
When the user clicks, use the distance from a point to a line algorithm to check each line to see if the click is within an acceptable distance of the line. Perhaps a few pixels. If more than one line is within an acceptable distance, perhaps choose the one that is closest.
You now know where in the array to insert the new point. It will be between the first and second points of the line that just matched.
If you do that, the shape drawing should just work.

Javascript Canvas how to shoot in 360* from a rotating object

All my searching comes up with more general arc/sin/cos usage or shooting to the mouse position.
I am looking to aim and fire a projectile with the keyboard and have done a lot of it from scratch, as a noob in a web class doing a project, but I am stuck on this. My current math got me to this mess in firing the shot in the direction the line is currently pointing... (code names cleaned for readability):
this.x = x + len * Math.cos(angle);
this.y = y + len * Math.sin(angle);
this.xmov = -((x + len * Math.cos(angle)) - x) / ((y + len * Math.sin(angle)) - y);
this.ymov = ((y + len * Math.sin(angle)) - y) / ((x + len * Math.cos(angle)) - x);
if (Math.abs(this.xmov) > Math.abs(this.ymov)) {
this.xmove = (this.xmov * Math.abs(this.ymov));
} else {
this.xmove = this.xmov;
}
if (Math.abs(this.ymov) > Math.abs(this.xmov)) {
this.ymove = (this.xmov * this.ymov);
} else {
this.ymove = this.ymov;
}
(And here is the full thing http://jsbin.com/ximatoq/edit. A and D to turn, S to fire (on release). Can also hold S while turning.)
... but, you'll see that it only works for 3/8's of it. What is the math to make this fire from a complete circle?

Use this as shoot function:
this.shoot = function() {
if (this.fire > 0) {
this.x = P1gun.x2;
this.y = P1gun.y2;
this.xmove = (P1gun.x2 - P1gun.x)/100;
this.ymove = (P1gun.y2 - P1gun.y)/100;
this.fire = 0;
this.firetravel = 1;
}
}
The /100 can be removed, but you have to reduce the projectile speed.
If you want to shoot gun2 change the P1gun to P2gun.

Normalising a vector.
To control the speed of something using a vector, first make the length of the vector 1 unit long (one pixel). This is commonly called normalising the vector, and sometimes it's called the unit vector. Then you can multiply that vector by any number to get the desired speed.
To normalise a vector first calculate its length, then divide it by that value.
function normalizeVector(v){
var len = Math.sqrt(v.x * v.x + v.y * v.y);
v.x /= len;
v.y /= len;
return v;
}
Trig
When you use trig to create a vector it is also a unit vector and does not need to be normalised.
function directioToUnitVector(angle){ // angle in radians
return {
x : cos(angle),
y : sin(angle)
}
Why normalise
Many many reasons, you build almost everything from unit vectors.
One example, if you have two points and want to move from one to the next at a speed of 10 pixels per second with a frame rate of 60frame per second.
var p1 = {};
var p2 = {};
p1.x = ? // the two points
p1.y = ?
p2.x = ?
p2.y = ?
// create a vector from p1 to p2
var v = {}
v.x = p2.x -p1.x;
v.y = p2.y -p1.y;
// Normalize the vector
normalizeVector(v);
var frameRate = 1/60; // 60 frames per second
var speed = 10; // ten pixels per second
function update(){
// scale vec to the speed you want. keeping the vec as a unit vec mean
// you can also change the speed, or use the time for even more precise
// speed control.
p1.x += v.x * (speed * frameRate);
p1.y += v.y * (speed * frameRate);
// draw the moving object at p1
requestAnimationFrame(update)
}
NOTE when normalizing you may get a vector that has no length. If your code is likely to create such a vector you need to check for the zero length and take appropriate action. Javascript does not throw an error when you divide by zero, but will return Infinity, with very strange results to your animations.

algorithm to randomly & efficiently place 100 circles without any overlap?

I am trying to write a script to place 100 circles of varying sizes onto a stage. I've outlined the concise requirements below.
Given the following:
var stage; // contains a "width" and "height" property.
var circle; // the circle class. contains x, y, radius & a unique id property.
var circleArray; // contains 100 circle instances
requirements:
write a function to place 100 circles of varying radius onto the stage.
placements must be random but evenly distributed (no clumping).
placement must be performant - this will be executing on a mobile web browser.
circles must not intersect/overlap other circles.
circle.x >= 0 must be true.
circle.y >= 0 && circle.y <= stage.height must be true.
circles may have any of the following radius sizes (assigned at creation):
150
120
90
80
65
My current attempt is a brute-force method, which does not operate efficiently. If I attempt to insert any more than ~10 circles, the browser hangs. Below is my current implementation, which I am completely OK with throwing away in favor of a more performant / better one.
Here is a live demo (NOTE: there is no actual drawing code, just the logic, but it will still lock up the browser so be warned!!) http://jsbin.com/muhiziduxu/2/edit?js,console
function adjustForOverlap (circleArray) {
// a reference to the circle that is invoking this function.
var _this = this;
// remove this circle from the array we are iterating over.
var arr = circleArray.filter(function (circle){
return circle.id !== _this.id;
});
// while repeat == true, the circle may be overlapping something.
var repeat = true;
while(repeat) {
var hasOverlap = false;
for (var i=0; i<arr.length; i++) {
var other = arr[i];
var dx = _self.x - other.x;
var dy = _self.y - other.y;
var rr = _self.radius + other.radius;
if (dx * dx + dy * dy < rr * rr) {
// if here, then an overlap was detected.
hit = true;
break;
}
}
// if hit is false, the circle didn't overlap anything, so break.
if (hit === false) {
repeat = false;
break;
} else {
// an overlap was detected, so randomize position.
_self.x = Math.random() * (stage.width*2);
_self.y = Math.random() * stage.height;
}
}
}

There are lots of efficient collision detection algorithms. Many of them work by dividing up the space into cells and maintaining a separate data structure with efficient lookup of other objects in the cell. The basic steps are:
Identify a random spot for your new circle
Determine which cells it's in
Look in each of those cells for a collision
If there's a collision, goto 1.
Else, add the new circle to each of the cells it overlaps.
You can use a simple square grid (i.e. a 2-d array) for the cell data structure, or something else like a quadtree. You can also in some cases get a bit of extra speed by trying a cheap-but-coarse collision check first (do the bounding boxes overlap), and if that returns true try the slightly more expensive and exact check.
Update
For quadtrees, check out d3-quadtree, which ought to give you a pretty good implementation, with examples.
For a (very quick, untested) 2-d array implementation:
function Grid(radius, width, height) {
// I'm not sure offhand how to find the optimum grid size.
// Let's use a radius as a starting point
this.gridX = Math.ceil(width / radius);
this.gridY = Math.ceil(height / radius);
// Determine cell size
this.cellWidth = width / this.gridX;
this.cellHeight = height / this.gridY;
// Create the grid structure
this.grid = [];
for (var i = 0; i < gridY; i++) {
// grid row
this.grid[i] = [];
for (var j = 0; j < gridX; j++) {
// Grid cell, holds refs to all circles
this.grid[i][j] = [];
}
}
}
Grid.prototype = {
// Return all cells the circle intersects. Each cell is an array
getCells: function(circle) {
var cells = [];
var grid = this.grid;
// For simplicity, just intersect the bounding boxes
var gridX1Index = Math.floor(
(circle.x - circle.radius) / this.cellWidth
);
var gridX2Index = Math.ceil(
(circle.x + circle.radius) / this.cellWidth
);
var gridY1Index = Math.floor(
(circle.y - circle.radius) / this.cellHeight
);
var gridY2Index = Math.ceil(
(circle.y + circle.radius) / this.cellHeight
);
for (var i = gridY1Index; i < gridY2Index; i++) {
for (var j = gridX1Index; j < gridX2Index; j++) {
// Add cell to list
cells.push(grid[i][j]);
}
}
return cells;
},
add: function(circle) {
this.getCells(circle).forEach(function(cell) {
cell.push(circle);
});
},
hasCollisions: function(circle) {
return this.getCells(circle).some(function(cell) {
return cell.some(function(other) {
return this.collides(circle, other);
}, this);
}, this);
},
collides: function (circle, other) {
if (circle === other) {
return false;
}
var dx = circle.x - other.x;
var dy = circle.y - other.y;
var rr = circle.radius + other.radius;
return (dx * dx + dy * dy < rr * rr);
}
};
var g = new Grid(150, 1000, 800);
g.add({x: 100, y: 100, radius: 50});
g.hasCollisions({x: 100, y:80, radius: 100});
Here's a fully-functional example: http://jsbin.com/cojoxoxufu/1/edit?js,output
Note that this only shows 30 circles. It looks like the problem is often unsolvable with your current radii, width, and height. This is set up to look for up to 500 locations for each circle before giving up and accepting a collision.

Collision detection: Separating Axis Theorem - Circle versus Polygon

I've been trying to implement collision detection between circles and polygons based on Randy Gaul's C++ Impulse Engine, following the code pretty closely, but the algorithm never returns true.
Here's the JSFiddle. (the bodies are rendered using the HTML5 Canvas API for convenience)
A snippet of the code (just collision detection):
const circPoly = (a, b) => {
let data = {},
center = a.pos;
data.contacts = [];
center = b.mat.clone().trans().mult(center.clone().sub(b.pos));
let sep = -Number.MAX_VALUE,
faceNorm = 0;
for (let i = 0; i < b.verts2.length; ++i) {
let sep2 = b.norms[i].dot(center.clone().sub(b.verts2[i]));
if (sep2 > a.radius) return data;
if (sep2 > sep) { sep = sep2; faceNorm = i; }
}
let v1 = b.verts2[faceNorm],
v2 = b.verts2[faceNorm + 1 < b.verts2.length ? faceNorm + 1 : 0];
if (sep < 0.0001) {
data.depth = a.radius;
data.norm = b.mat.clone().mult(b.norms[faceNorm]).neg();
data.contacts[0] = data.norm.clone().vmult(a.pos.clone().sadd(a.radius));
return data;
}
let dot1 = center.clone().sub(v1).dot(v2.clone().sub(v1)),
dot2 = center.clone().sub(v2).dot(v1.clone().sub(v2));
data.depth = a.radius - sep;
if (dot1 <= 0) {
if (center.dist2(v1) > a.radius * a.radius) return data;
let norm = v1.clone().sub(center);
norm = b.mat.clone().mult(norm);
norm.norm();
data.norm = norm;
v1 = b.mat.clone().mult(v1.clone().add(b.pos));
data.contacts[0] = v1;
} else if (dot2 <= 0) {
if (center.dist2(v2) > a.radius * a.radius) return data;
let norm = v2.clone().sub(center);
norm = b.mat.clone().mult(norm);
norm.norm();
data.norm = norm;
v2 = b.mat.clone().mult(v2.clone().add(b.pos));
data.contacts[0] = v2;
} else {
let norm = b.norms[faceNorm];
if (center.clone().sub(v1).dot(norm) > a.radius) return data;
norm = b.mat.clone().mult(norm);
data.norm = norm.clone().neg();
data.contacts[0] = data.norm.clone().vmult(a.pos.clone().sadd(a.radius));
}
return data;
};
Note that b.verts2 refers to the polygon's vertices in real world coordinates.
I know for a fact that there are no problems with the Vector class but as I don't exactly have very much experience with transformation matrices, that class could be the root of these errors, although the code for it is pretty much entirely derived from the Impulse Engine as well, so it should work. As mentioned before, the algorithm always returns false, even when a collision really has occurred. What am I doing wrong here? I tried taking out the early returns, but that just returns weird results like contact points with negative coordinates which obviously is not quite correct.
EDIT: Modified my vector class's perpendicular function to work the same way as the Impulse Engine's (both ways are right, but I think one is clockwise and the other one counterclockwise -- I also modified my vertices to reflect the counterclockwise-ness). Unfortunately, it still fails the test.
https://jsfiddle.net/khanfused/tv359kgL/4/

Well the are many problems and I really dont understand what you are trying to do as it seem overly complex. Eg why does matrix have trans??? and why are you using the Y up screen as the coordinate system for the transform??? (rhetorical)
In the first loop.
The first is that you are testing the distance of the normal vectors
of each vert, should be testing the vert position.
Also you are finding the distance using the vec.dot function that
returns the square of the distance. But you test for the radius, you
should be testing for if(sep2 < radius * radius)
And you have the comparison the wrong way around you should be
testing if less than radius squared (not greater than)
Then when you do detect a vert within the radius you return the data
object but forget to put the vert that was found inside the circle on
the data.contacts array.
I am not sure what the intention of keeping the index of the most
distant vect is but then the rest of the function make zero sense to
me???? :( and I have tried to understand it.
All you need to do is
A check if any verts on the poly are closer than radius, if so then you have a intercept (or is completely inside)
Then you need to check the distance of each line segment
Can be done for each line segment with the following if you dont need the intercepts (or below that if you need intercepts) only use one or the other.
// circle is a point {x:?,y:?}
// radius = is the you know what
// p1,p2 are the start and end points of a line
checkLineCircle = function(circle,radius,p1,p2){
var v1 = {};
var v2 = {};
var v3 = {};
var u;
// get dist to end of line
v2.x = circle.x - p1.x;
v2.y = circle.y - p1.y;
// check if end points are inside the circle
if( Math.min(
Math.hypot(p2.x - circle.x, p2.y - circle.y),
Math.hypot(v2.x, v2.y)
) <= radius){
return true;
}
// get the line as a vector
v1.x = p2.x - p1.x;
v1.y = p2.y - p1.y;
// get the unit distance of the closest point on the line
u = (v2.x * v1.x + v2.y * v1.y)/(v1.y * v1.y + v1.x * v1.x);
// is this on the line segment
if(u >= 0 && u <= 1){
v3.x = v1.x * u; // get the point on the line segment
v3.y = v1.y * u;
// get the distance to that point and return true or false depending on the
// it being inside the circle
return (Math.hypot(v3.y - v2.y, v3.x - v2.x) <= radius);
}
return false; // no intercept
}
Do that for each line.To save time transform the circle center to the polygon local, rather than transform each point on the poly.
If you need the points of intercept then use the following function
// p1,p2 are the start and end points of a line
// returns an array empty if no points found or one or two points depending on the number of intercepts found
// If two points found the first point in the array is the point closest to the line start (p1)
function circleLineIntercept(circle,radius,p1,p2){
var v1 = {};
var v2 = {};
var ret = [];
var u1,u2,b,c,d;
// line as vector
v1.x = p2.x - p1.x;
v1.y = p2.y - p1.y;
// vector to circle center
v2.x = p1.x - circle.x;
v2.y = p1.y - circle.y;
// dot of line and circle
b = (v1.x * v2.x + v1.y * v2.y) * -2;
// length of line squared * 2
c = 2 * (v1.x * v1.x + v1.y * v1.y);
// some math to solve the two triangles made by the intercept points, the circle center and the perpendicular line to the line.
d = Math.sqrt(b * b - 2 * c * (v2.x * v2.x + v2.y * v2.y - radius * radius));
// will give a NaN if no solution
if(isNaN(d)){ // no intercept
return ret;
}
// get the unit distance of each intercept to the line
u1 = (b - d) / c;
u2 = (b + d) / c;
// check the intercept is on the line segment
if(u1 <= 1 && u1 >= 0){
ret.push({x:line.p1.x + v1.x * u1, y : line.p1.y + v1.y * u1 });
}
// check the intercept is on the line segment
if(u2 <= 1 && u2 >= 0){
ret.push({x:line.p1.x + v1.x * u2, y : line.p1.y + v1.y * u2});
}
return ret;
}
I will leave it up to you to do the polygon iteration.