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separator.js
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separator.js
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ig.module('plugins.joncom.box2d.separator')
.requires('plugins.joncom.box2d.lib')
.defines(function(){
// Replaced .call(this) with .call(window) to make globally accessible.
// Original JavaScript found here:
// https://raw.github.com/isaksky/asteroids/master/source/js/box_2d_separator.js
/*
* Convex Separator for Box2D Web
*
* This is a port of an Actionscript class written by Antoan Angelov.
* See http://www.emanueleferonato.com/2011/09/12/create-non-convex-complex-shapes-with-box2d/
* It is designed to work with Erin Catto's Box2D physics library.
*/
(function() {
var b2PolygonShape = Box2D.Collision.Shapes.b2PolygonShape;
var b2Vec2 = Box2D.Common.Math.b2Vec2;
var b2Body = Box2D.Dynamics.b2Body;
var b2FixtureDef = Box2D.Dynamics.b2FixtureDef;
/**
* Separates a non-convex polygon into convex polygons and adds them as fixtures to the <code>body</code> parameter.<br/>
* There are some rules you should follow (otherwise you might get unexpected results) :
* <ul>
* <li>This class is specifically for non-convex polygons. If you want to create a convex polygon, you don't need to use this class - Box2D's <code>b2PolygonShape</code> class allows you to create convex shapes with the <code>setAsArray()</code>/<code>setAsVector()</code> method.</li>
* <li>The vertices must be in clockwise order.</li>
* <li>No three neighbouring points should lie on the same line segment.</li>
* <li>There must be no overlapping segments and no "holes".</li>
* </ul> <p/>
* @param body The b2Body, in which the new fixtures will be stored.
* @param fixtureDef A b2FixtureDef, containing all the properties (friction, density, etc.) which the new fixtures will inherit.
* @param verticesAry The vertices of the non-convex polygon, in clockwise order.
* @param scale <code>[optional]</code> The scale which you use to draw shapes in Box2D. The bigger the scale, the better the precision. The default value is 30.
* @see b2PolygonShape
* @see b2PolygonShape.SetAsArray()
* @see b2PolygonShape.SetAsVector()
* @see b2Fixture
* */
var separate = function(body, fixtureDef, verticesAry, scale) {
scale = scale != null ? scale : 30;
var i, n = verticesAry.length,
j, m;
var vec = [],
figsAry;
var polyShape;
for (i = 0; i < n; i++) {
vec.push(new b2Vec2(verticesAry[i].x * scale, verticesAry[i].y * scale));
}
figsAry = calcShapes(vec);
n = figsAry.length;
for (i = 0; i < n; i++) {
verticesAry = [];
vec = figsAry[i];
m = vec.length;
for (j = 0; j < m; j++) {
verticesAry.push(new b2Vec2(vec[j].x / scale, vec[j].y / scale));
}
polyShape = new b2PolygonShape;
polyShape.SetAsVector(verticesAry);
fixtureDef.shape = polyShape;
body.CreateFixture(fixtureDef);
}
}
/**
* Checks whether the vertices in <code>verticesVec</code> can be properly distributed into the new fixtures (more specifically, it makes sure there are no overlapping segments and the vertices are in clockwise order).
* It is recommended that you use this method for debugging only, because it may cost more CPU usage.
* <p/>
* @param verticesVec The vertices to be validated.
* @return An integer which can have the following values:
* <ul>
* <li>0 if the vertices can be properly processed.</li>
* <li>1 If there are overlapping lines.</li>
* <li>2 if the points are <b>not</b> in clockwise order.</li>
* <li>3 if there are overlapping lines <b>and</b> the points are <b>not</b> in clockwise order.</li>
* </ul>
* */
var validate = function(verticesAry) {
var i, n = verticesAry.length,
j, j2, i2, i3, d, ret = 0;
var fl, fl2 = false;
for (i = 0; i < n; i++) {
i2 = (i < n - 1) ? i + 1 : 0;
i3 = (i > 0) ? i - 1 : n - 1;
fl = false;
for (j = 0; j < n; j++) {
if (((j != i) && j != i2)) {
if (!fl) {
d = det(verticesAry[i].x, verticesAry[i].y, verticesAry[i2].x, verticesAry[i2].y, verticesAry[j].x, verticesAry[j].y);
if ((d > 0)) {
fl = true;
}
}
if ((j != i3)) {
j2 = (j < n - 1) ? j + 1 : 0;
if (hitSegment(verticesAry[i].x, verticesAry[i].y, verticesAry[i2].x, verticesAry[i2].y, verticesAry[j].x, verticesAry[j].y, verticesAry[j2].x, verticesAry[j2].y)) {
ret = 1;
}
}
}
}
if (!fl) {
fl2 = true;
}
}
if (fl2) {
if ((ret == 1)) {
ret = 3;
} else {
ret = 2;
}
}
return ret;
}
var calcShapes = function(verticesAry) {
var vec;
var i, n, j;
var d, t, dx, dy, minLen;
var i1, i2, i3, p1, p2, p3;
var j1, j2, v1, v2, k, h;
var vec1, vec2;
var v, hitV;
var isConvex;
var figsAry = [],
queue = [];
queue.push(verticesAry);
while (queue.length) {
vec = queue[0];
n = vec.length;
isConvex = true;
for (i = 0; i < n; i++) {
i1 = i;
i2 = (i < n - 1) ? i + 1 : i + 1 - n;
i3 = (i < n - 2) ? i + 2 : i + 2 - n;
p1 = vec[i1];
p2 = vec[i2];
p3 = vec[i3];
d = det(p1.x, p1.y, p2.x, p2.y, p3.x, p3.y);
if ((d < 0)) {
isConvex = false;
minLen = Number.MAX_VALUE;
for (j = 0; j < n; j++) {
if (((j != i1) && j != i2)) {
j1 = j;
j2 = (j < n - 1) ? j + 1 : 0;
v1 = vec[j1];
v2 = vec[j2];
v = hitRay(p1.x, p1.y, p2.x, p2.y, v1.x, v1.y, v2.x, v2.y);
if (v) {
dx = p2.x - v.x;
dy = p2.y - v.y;
t = dx * dx + dy * dy;
if ((t < minLen)) {
h = j1;
k = j2;
hitV = v;
minLen = t;
}
}
}
}
if ((minLen == Number.MAX_VALUE)) {
err();
}
vec1 = [];
vec2 = [];
j1 = h;
j2 = k;
v1 = vec[j1];
v2 = vec[j2];
if (!pointsMatch(hitV.x, hitV.y, v2.x, v2.y)) {
vec1.push(hitV);
}
if (!pointsMatch(hitV.x, hitV.y, v1.x, v1.y)) {
vec2.push(hitV);
}
h = -1;
k = i1;
while (true) {
if ((k != j2)) {
vec1.push(vec[k]);
} else {
if (((h < 0) || h >= n)) {
err();
}
if (!isOnSegment(v2.x, v2.y, vec[h].x, vec[h].y, p1.x, p1.y)) {
vec1.push(vec[k]);
}
break;
}
h = k;
if (((k - 1) < 0)) {
k = n - 1;
} else {
k--;
}
}
vec1 = vec1.reverse();
h = -1;
k = i2;
while (true) {
if ((k != j1)) {
vec2.push(vec[k]);
} else {
if (((h < 0) || h >= n)) {
err();
}
if (((k == j1) && !isOnSegment(v1.x, v1.y, vec[h].x, vec[h].y, p2.x, p2.y))) {
vec2.push(vec[k]);
}
break;
}
h = k;
if (((k + 1) > n - 1)) {
k = 0;
} else {
k++;
}
}
queue.push(vec1, vec2);
queue.shift();
break;
}
}
if (isConvex) {
figsAry.push(queue.shift());
}
}
return figsAry;
}
var hitRay = function(x1, y1, x2, y2, x3, y3, x4, y4) {
var t1 = x3 - x1,
t2 = y3 - y1,
t3 = x2 - x1,
t4 = y2 - y1,
t5 = x4 - x3,
t6 = y4 - y3,
t7 = t4 * t5 - t3 * t6,
a;
a = (((t5 * t2) - t6 * t1) / t7);
var px = x1 + a * t3,
py = y1 + a * t4;
var b1 = isOnSegment(x2, y2, x1, y1, px, py);
var b2 = isOnSegment(px, py, x3, y3, x4, y4);
if ((b1 && b2)) {
return new b2Vec2(px, py);
}
return null;
}
var hitSegment = function(x1, y1, x2, y2, x3, y3, x4, y4) {
var t1 = x3 - x1,
t2 = y3 - y1,
t3 = x2 - x1,
t4 = y2 - y1,
t5 = x4 - x3,
t6 = y4 - y3,
t7 = t4 * t5 - t3 * t6,
a;
a = (((t5 * t2) - t6 * t1) / t7);
var px = x1 + a * t3,
py = y1 + a * t4;
var b1 = isOnSegment(px, py, x1, y1, x2, y2);
var b2 = isOnSegment(px, py, x3, y3, x4, y4);
if ((b1 && b2)) {
return new b2Vec2(px, py);
}
return null;
}
var isOnSegment = function(px, py, x1, y1, x2, y2) {
var b1 = ((((x1 + 0.1) >= px) && px >= x2 - 0.1) || (((x1 - 0.1) <= px) && px <= x2 + 0.1));
var b2 = ((((y1 + 0.1) >= py) && py >= y2 - 0.1) || (((y1 - 0.1) <= py) && py <= y2 + 0.1));
return ((b1 && b2) && isOnLine(px, py, x1, y1, x2, y2));
}
var pointsMatch = function(x1, y1, x2, y2) {
var dx = (x2 >= x1) ? x2 - x1 : x1 - x2,
dy = (y2 >= y1) ? y2 - y1 : y1 - y2;
return ((dx < 0.1) && dy < 0.1);
}
var isOnLine = function(px, py, x1, y1, x2, y2) {
if ((((x2 - x1) > 0.1) || x1 - x2 > 0.1)) {
var a = (y2 - y1) / (x2 - x1),
possibleY = a * (px - x1) + y1,
diff = (possibleY > py) ? possibleY - py : py - possibleY;
return (diff < 0.1);
}
return (((px - x1) < 0.1) || x1 - px < 0.1);
}
var det = function det(x1, y1, x2, y2, x3, y3) {
return x1 * y2 + x2 * y3 + x3 * y1 - y1 * x2 - y2 * x3 - y3 * x1;
}
var err = function err() {
throw new Error("A problem has occurred. Use the Validate() method to see where the problem is.");
}
this.Box2DSeparator = {
separate: separate,
validate: validate
};
}).call(window);
});