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collision.js
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/*
* SPDX-FileCopyrightText: 2018 Andrew Sevenson <[email protected]>
* SPDX-FileCopyrightText: 2019 Petr Pucil <[email protected]>
*
* SPDX-License-Identifier: MIT
*/
var Vector = function(p1, p2) {
this.x = (p1 && p2) ? p2.x-p1.x : (p1 ? p1.x : 0);
this.y = (p1 && p2) ? p2.y-p1.y : (p1 ? p1.y : 0);
this.length = Math.sqrt(this.x*this.x + this.y*this.y) || 0;
this.plus = function(v2) {
return new Vector(
{x: this.x+v2.x, y: this.y+v2.y}
);
}
this.minus = function(v2) {
return new Vector(
{x: this.x-v2.x, y: this.y-v2.y}
);
}
this.multiply = function(num) {
return new Vector(
{x:this.x*num, y:this.y*num}
);
}
this.normalize = function() {
var len = this.length;
if(len > 0) {
return new Vector(
{x: this.x / len, y: this.y / len}
);
} else {
return false;
}
}
this.leftHand = function() {
return new Vector(
{x:this.y, y:-this.x}
);
}
this.rightHand = function() {
return new Vector(
{x:-this.y, y:this.x}
);
}
this.dotProduct = function(v2) {
return this.x*v2.x+this.y*v2.y;
}
}
// taken from https://github.com/sevdanski/SAT_AS3 (just rewritten to JavaScript)
var Collision = new function() {
/*
circle format: {x: 20, y: 15, r: 5}
polygon format: {x: 110, y: 40, points: [{x: 10, y: 15}, {x: 20, y: 45}, {x: 40, y: 45}, ...]}
*/
// static private
function getAxisNormal(points, i) {
var p1 = points[i],
p2 = (i >= points.length - 1) ? points[0] : points[i + 1];
var axis = new Vector(p1, p2).rightHand().normalize();
return axis;
}
// static public
this.circleToCircle = function(circ1, circ2) {
var rsum = circ1.r + circ2.r;
var dx = (circ2.x - circ1.x),
dy = (circ2.y - circ1.y);
var cdistsquared = (dx * dx) + (dy * dy),
rsumsquared = rsum * rsum;
if(cdistsquared > rsumsquared) {
// gap found
return null;
}
var result = {};
var cv = new Vector(circ1, circ2);
result.vector = cv.normalize();
result.distance = cv.length - rsum;
result.separation = result.vector.multiply(result.distance);
result.shapeAContained = (circ1.r <= circ2.r && cv.length <= circ2.r-circ1.r);
result.shapeBContained = (circ2.r <= circ1.r && cv.length <= circ1.r-circ2.r);
return result;
}
this.polygonToPolygon = function(obj1, obj2) {
var result = {shapeAContained: true, shapeBContained: true};
var shortestDist = +Infinity;
var obj1pnt = obj1.points,
obj2pnt = obj2.points;
var obj1pntlen = obj1pnt.length,
obj2pntlen = obj2pnt.length;
var vOffset = new Vector(obj1).minus(obj2);
for(var i = 0; i < obj1pntlen; i++) {
var axis = getAxisNormal(obj1pnt, i),
min0, max0, min1, max1;
min0 = max0 = axis.dotProduct(obj1pnt[0]);
for (var a = 1; a < obj1pntlen; a++) {
var t = axis.dotProduct(obj1pnt[a]);
if (t < min0) min0 = t;
if (t > max0) max0 = t;
}
min1 = max1 = axis.dotProduct(obj2pnt[0]);
for (var b = 1; b < obj2pntlen; b++) {
var t = axis.dotProduct(obj2pnt[b]);
if (t < min1) min1 = t;
if (t > max1) max1 = t;
}
var sOffset = axis.dotProduct(vOffset);
min0 += sOffset;
max0 += sOffset;
var d0 = min0 - max1,
d1 = min1 - max0;
if (d0 > 0 || d1 > 0) {
// gap found
return null;
}
if (max0 < max1 || min0 > min1) result.shapeAContained = false;
if (max1 < max0 || min1 > min0) result.shapeBContained = false;
var distmin = d0,
distminAbs = Math.abs(distmin);
if (distminAbs < shortestDist) {
// this distance is shorter so use it...
result.distance = distmin;
result.vector = axis;
shortestDist = distminAbs;
}
}
result.separation = result.vector.multiply(result.distance);
return result;
}
this.circleToPolygon = function(circ, plg) {
var result = {shapeAContained: true, shapeBContained: true},
shortestDist = +Infinity;
var plgpnt = plg.points;
var plglen = plgpnt.length;
var vOffset = new Vector(plg).minus(circ);
var closestVertex = new Vector();
var smallestPcDist = +Infinity;
for(var a = 0; a < plglen; a++) {
var dx = (circ.x - (plg.x + plgpnt[a].x)),
dy = (circ.y - (plg.y + plgpnt[a].y));
var pcDistSquared = (dx * dx + dy * dy);
if(pcDistSquared < smallestPcDist) {
closestVertex.x = plg.x + plgpnt[a].x;
closestVertex.y = plg.y + plgpnt[a].y;
smallestPcDist = pcDistSquared;
}
}
var axis = closestVertex.minus(circ).normalize();
var min0, max0, min1, max1;
min0 = max0 = axis.dotProduct(plgpnt[0]);
for (var b = 1; b < plglen; b++) {
var t = axis.dotProduct(plgpnt[b]);
if (t < min0) min0 = t;
if (t > max0) max0 = t;
}
min1 = axis.dotProduct(new Vector({x:0, y:0}));
max1 = min1 + circ.r;
min1 -= circ.r;
var sOffset = axis.dotProduct(vOffset);
min0 += sOffset;
max0 += sOffset;
var d0 = min0 - max1,
d1 = min1 - max0;
if (d0 > 0 || d1 > 0) {
// gap found
return null;
}
if (max0 < max1 || min0 > min1) result.shapeAContained = false;
if (max1 < max0 || min1 > min0) result.shapeBContained = false;
var distmin = d0,
distminAbs = Math.abs(distmin);
result.distance = distmin;
result.vector = axis;
shortestDist = distminAbs;
for(var i = 0; i < plglen; i++) {
var axis = getAxisNormal(plgpnt, i),
min0, max0, min1, max1;
min0 = max0 = axis.dotProduct(plgpnt[0]);
for (var a = 1; a < plglen; a++) {
var t = axis.dotProduct(plgpnt[a]);
if (t < min0) min0 = t;
if (t > max0) max0 = t;
}
min1 = axis.dotProduct(new Vector({x:0, y:0}));
max1 = min1 + circ.r;
min1 -= circ.r;
sOffset = axis.dotProduct(vOffset);
min0 += sOffset;
max0 += sOffset;
var d0 = min0 - max1,
d1 = min1 - max0;
if (d0 > 0 || d1 > 0) {
// gap found
return null;
}
if (max0 < max1 || min0 > min1) result.shapeAContained = false;
if (max1 < max0 || min1 > min0) result.shapeBContained = false;
var distmin = d0,
distminAbs = Math.abs(distmin);
if (distminAbs < shortestDist) {
// this distance is shorter so use it...
result.distance = distmin;
result.vector = axis;
shortestDist = distminAbs;
}
}
result.separation = result.vector.multiply(result.distance);
return result;
}
}