// Version 0.2 - Copyright 2013 - Jim Riecken <jimr@jimr.ca>
//
// Released under the MIT License - https://github.com/jriecken/sat-js
//
// A simple library for determining intersections of circles and
// polygons using the Separating Axis Theorem.
/** @preserve SAT.js - Version 0.2 - Copyright 2013 - Jim Riecken <jimr@jimr.ca> - released under the MIT License. https://github.com/jriecken/sat-js */
var SAT = (function () {
"use strict";
var SAT = {};
//
// ## Vector
//
// Represents a vector in two dimensions with `x` and `y` properties.
// Create a new Vector, optionally passing in the `x` and `y` coordinates. If
// a coordinate is not specified, it will be set to `0`
/**
* @param {?number=} x The x position.
* @param {?number=} y The y position.
* @constructor
*/
function Vector(x, y) {
this['x'] = x || 0;
this['y'] = y || 0;
}
SAT['Vector'] = Vector;
// Alias `Vector` as `V`
SAT['V'] = Vector;
// Copy the values of another Vector into this one.
/**
* @param {Vector} other The other Vector.
* @return {Vector} This for chaining.
*/
Vector.prototype['copy'] = Vector.prototype.copy = function(other) {
this['x'] = other['x'];
this['y'] = other['y'];
return this;
};
// Change this vector to be perpendicular to what it was before. (Effectively
// roatates it 90 degrees in a clockwise direction)
/**
* @return {Vector} This for chaining.
*/
Vector.prototype['perp'] = Vector.prototype.perp = function() {
var x = this['x'];
this['x'] = this['y'];
this['y'] = -x;
return this;
};
// Rotate this vector (counter-clockwise) by the specified angle (in radians).
/**
* @param {number} angle The angle to rotate (in radians)
* @return {Vector} This for chaining.
*/
Vector.prototype['rotate'] = Vector.prototype.rotate = function (angle) {
var x = this['x'];
var y = this['y'];
this['x'] = x * Math.cos(angle) - y * Math.sin(angle);
this['y'] = x * Math.sin(angle) + y * Math.cos(angle);
return this;
};
// Rotate this vector (counter-clockwise) by the specified angle (in radians) which has already been calculated into sin and cos.
/**
* @param {number} sin - The Math.sin(angle)
* @param {number} cos - The Math.cos(angle)
* @return {Vector} This for chaining.
*/
Vector.prototype['rotatePrecalc'] = Vector.prototype.rotatePrecalc = function (sin, cos) {
var x = this['x'];
var y = this['y'];
this['x'] = x * cos - y * sin;
this['y'] = x * sin + y * cos;
return this;
};
// Reverse this vector.
/**
* @return {Vector} This for chaining.
*/
Vector.prototype['reverse'] = Vector.prototype.reverse = function() {
this['x'] = -this['x'];
this['y'] = -this['y'];
return this;
};
// Normalize this vector. (make it have length of `1`)
/**
* @return {Vector} This for chaining.
*/
Vector.prototype['normalize'] = Vector.prototype.normalize = function() {
var d = this.len();
if(d > 0) {
this['x'] = this['x'] / d;
this['y'] = this['y'] / d;
}
return this;
};
// Add another vector to this one.
/**
* @param {Vector} other The other Vector.
* @return {Vector} This for chaining.
*/
Vector.prototype['add'] = Vector.prototype.add = function(other) {
this['x'] += other['x'];
this['y'] += other['y'];
return this;
};
// Subtract another vector from this one.
/**
* @param {Vector} other The other Vector.
* @return {Vector} This for chaiing.
*/
Vector.prototype['sub'] = Vector.prototype.sub = function(other) {
this['x'] -= other['x'];
this['y'] -= other['y'];
return this;
};
// Scale this vector. An independant scaling factor can be provided
// for each axis, or a single scaling factor that will scale both `x` and `y`.
/**
* @param {number} x The scaling factor in the x direction.
* @param {?number=} y The scaling factor in the y direction. If this
* is not specified, the x scaling factor will be used.
* @return {Vector} This for chaining.
*/
Vector.prototype['scale'] = Vector.prototype.scale = function(x,y) {
this['x'] *= x;
this['y'] *= y || x;
return this;
};
// Project this vector on to another vector.
/**
* @param {Vector} other The vector to project onto.
* @return {Vector} This for chaining.
*/
Vector.prototype['project'] = Vector.prototype.project = function(other) {
var amt = this.dot(other) / other.len2();
this['x'] = amt * other['x'];
this['y'] = amt * other['y'];
return this;
};
// Project this vector onto a vector of unit length. This is slightly more efficient
// than `project` when dealing with unit vectors.
/**
* @param {Vector} other The unit vector to project onto.
* @return {Vector} This for chaining.
*/
Vector.prototype['projectN'] = Vector.prototype.projectN = function(other) {
var amt = this.dot(other);
this['x'] = amt * other['x'];
this['y'] = amt * other['y'];
return this;
};
// Reflect this vector on an arbitrary axis.
/**
* @param {Vector} axis The vector representing the axis.
* @return {Vector} This for chaining.
*/
Vector.prototype['reflect'] = Vector.prototype.reflect = function(axis) {
var x = this['x'];
var y = this['y'];
this.project(axis).scale(2);
this['x'] -= x;
this['y'] -= y;
return this;
};
// Reflect this vector on an arbitrary axis (represented by a unit vector). This is
// slightly more efficient than `reflect` when dealing with an axis that is a unit vector.
/**
* @param {Vector} axis The unit vector representing the axis.
* @return {Vector} This for chaining.
*/
Vector.prototype['reflectN'] = Vector.prototype.reflectN = function(axis) {
var x = this['x'];
var y = this['y'];
this.projectN(axis).scale(2);
this['x'] -= x;
this['y'] -= y;
return this;
};
// Get the dot product of this vector and another.
/**
* @param {Vector} other The vector to dot this one against.
* @return {number} The dot product.
*/
Vector.prototype['dot'] = Vector.prototype.dot = function(other) {
return this['x'] * other['x'] + this['y'] * other['y'];
};
// Get the squared length of this vector.
/**
* @return {number} The length^2 of this vector.
*/
Vector.prototype['len2'] = Vector.prototype.len2 = function() {
return this.dot(this);
};
// Get the length of this vector.
/**
* @return {number} The length of this vector.
*/
Vector.prototype['len'] = Vector.prototype.len = function() {
return Math.sqrt(this.len2());
};
// ## Circle
//
// Represents a circle with a position and a radius.
// Create a new circle, optionally passing in a position and/or radius. If no position
// is given, the circle will be at `(0,0)`. If no radius is provided, the circle will
// have a radius of `0`.
/**
* @param {Vector=} pos A vector representing the position of the center of the circle
* @param {?number=} r The radius of the circle
* @constructor
*/
function Circle(pos, r) {
this['pos'] = pos || new Vector();
this['r'] = r || 0;
}
SAT['Circle'] = Circle;
// ## Polygon
//
// Represents a *convex* polygon with any number of points (specified in counter-clockwise order)
//
// The edges/normals of the polygon will be calculated on creation and stored in the
// `edges` and `normals` properties. If you change the polygon's points, you will need
// to call `recalc` to recalculate the edges/normals.
// Create a new polygon, passing in a position vector, and an array of points (represented
// by vectors relative to the position vector). If no position is passed in, the position
// of the polygon will be `(0,0)`.
/**
* @param {Vector=} pos A vector representing the origin of the polygon. (all other
* points are relative to this one)
* @param {Array.<Vector>=} points An array of vectors representing the points in the polygon,
* in counter-clockwise order.
* @constructor
*/
function Polygon(pos, points) {
this['pos'] = pos || new Vector();
this['points'] = points || [];
this.recalc();
}
SAT['Polygon'] = Polygon;
// Recalculates the edges and normals of the polygon. This **must** be called
// if the `points` array is modified at all and the edges or normals are to be
// accessed.
/**
* @return {Polygon} This for chaining.
*/
Polygon.prototype['recalc'] = Polygon.prototype.recalc = function() {
// The edges here are the direction of the `n`th edge of the polygon, relative to
// the `n`th point. If you want to draw a given edge from the edge value, you must
// first translate to the position of the starting point.
this['edges'] = [];
// The normals here are the direction of the normal for the `n`th edge of the polygon, relative
// to the position of the `n`th point. If you want to draw an edge normal, you must first
// translate to the position of the starting point.
this['normals'] = [];
var points = this['points'];
var len = points.length;
for (var i = 0; i < len; i++) {
var p1 = points[i];
var p2 = i < len - 1 ? points[i + 1] : points[0];
var e = new Vector().copy(p2).sub(p1);
var n = new Vector().copy(e).perp().normalize();
this['edges'].push(e);
this['normals'].push(n);
}
return this;
};
// Rotates this polygon counter-clockwise around the origin of *its local coordinate system* (i.e. `pos`).
//
// Note: You do **not** need to call `recalc` after rotation.
/**
* @param {number} angle The angle to rotate (in radians)
* @return {Polygon} This for chaining.
*/
Polygon.prototype['rotate'] = Polygon.prototype.rotate = function(angle) {
var i;
var points = this['points'];
var edges = this['edges'];
var normals = this['normals'];
var len = points.length;
// Calc it just the once, rather than 4 times per array element
var cos = Math.cos(angle);
var sin = Math.sin(angle);
for (i = 0; i < len; i++) {
points[i].rotatePrecalc(sin, cos);
edges[i].rotatePrecalc(sin, cos);
normals[i].rotatePrecalc(sin, cos);
}
return this;
};
// Rotates this polygon counter-clockwise around the origin of *its local coordinate system* (i.e. `pos`).
//
// Note: You do **not** need to call `recalc` after rotation.
/**
* @param {number} angle The angle to rotate (in radians)
* @return {Polygon} This for chaining.
*/
Polygon.prototype['scale'] = Polygon.prototype.scale = function(x, y) {
var i;
var points = this['points'];
var edges = this['edges'];
var normals = this['normals'];
var len = points.length;
for (i = 0; i < len; i++) {
points[i].scale(x,y);
edges[i].scale(x,y);
normals[i].scale(x,y);
}
return this;
};
// Translates the points of this polygon by a specified amount relative to the origin of *its own coordinate
// system* (i.e. `pos`).
//
// This is most useful to change the "center point" of a polygon.
//
// Note: You do **not** need to call `recalc` after translation.
/**
* @param {number} x The horizontal amount to translate.
* @param {number} y The vertical amount to translate.
* @return {Polygon} This for chaining.
*/
Polygon.prototype['translate'] = Polygon.prototype.translate = function (x, y) {
var i;
var points = this['points'];
var len = points.length;
for (i = 0; i < len; i++) {
points[i].x += x;
points[i].y += y;
}
return this;
};
// ## Box
//
// Represents an axis-aligned box, with a width and height.
// Create a new box, with the specified position, width, and height. If no position
// is given, the position will be `(0,0)`. If no width or height are given, they will
// be set to `0`.
/**
* @param {Vector=} pos A vector representing the top-left of the box.
* @param {?number=} w The width of the box.
* @param {?number=} h The height of the box.
* @constructor
*/
function Box(pos, w, h) {
this['pos'] = pos || new Vector();
this['w'] = w || 0;
this['h'] = h || 0;
}
SAT['Box'] = Box;
// Returns a polygon whose edges are the same as this box.
/**
* @return {Polygon} A new Polygon that represents this box.
*/
Box.prototype['toPolygon'] = Box.prototype.toPolygon = function() {
var pos = this['pos'];
var w = this['w'];
var h = this['h'];
return new Polygon(new Vector(pos['x'], pos['y']), [
new Vector(), new Vector(w, 0),
new Vector(w,h), new Vector(0,h)
]);
};
// ## Response
//
// An object representing the result of an intersection. Contains:
// - The two objects participating in the intersection
// - The vector representing the minimum change necessary to extract the first object
// from the second one (as well as a unit vector in that direction and the magnitude
// of the overlap)
// - Whether the first object is entirely inside the second, and vice versa.
/**
* @constructor
*/
function Response() {
this['a'] = null;
this['b'] = null;
this['overlapN'] = new Vector();
this['overlapV'] = new Vector();
this.clear();
}
SAT['Response'] = Response;
// Set some values of the response back to their defaults. Call this between tests if
// you are going to reuse a single Response object for multiple intersection tests (recommented
// as it will avoid allcating extra memory)
/**
* @return {Response} This for chaining
*/
Response.prototype['clear'] = Response.prototype.clear = function() {
this['aInB'] = true;
this['bInA'] = true;
this['overlap'] = Number.MAX_VALUE;
return this;
};
// ## Object Pools
// A pool of `Vector` objects that are used in calculations to avoid
// allocating memory.
/**
* @type {Array.<Vector>}
*/
var T_VECTORS = [];
for (var i = 0; i < 10; i++) { T_VECTORS.push(new Vector()); }
// A pool of arrays of numbers used in calculations to avoid allocating
// memory.
/**
* @type {Array.<Array.<number>>}
*/
var T_ARRAYS = [];
for (var i = 0; i < 5; i++) { T_ARRAYS.push([]); }
// ## Helper Functions
// Flattens the specified array of points onto a unit vector axis,
// resulting in a one dimensional range of the minimum and
// maximum value on that axis.
/**
* @param {Array.<Vector>} points The points to flatten.
* @param {Vector} normal The unit vector axis to flatten on.
* @param {Array.<number>} result An array. After calling this function,
* result[0] will be the minimum value,
* result[1] will be the maximum value.
*/
function flattenPointsOn(points, normal, result) {
var min = Number.MAX_VALUE;
var max = -Number.MAX_VALUE;
var len = points.length;
for (var i = 0; i < len; i++ ) {
// The magnitude of the projection of the point onto the normal
var dot = points[i].dot(normal);
if (dot < min) { min = dot; }
if (dot > max) { max = dot; }
}
result[0] = min; result[1] = max;
}
// Check whether two convex polygons are separated by the specified
// axis (must be a unit vector).
/**
* @param {Vector} aPos The position of the first polygon.
* @param {Vector} bPos The position of the second polygon.
* @param {Array.<Vector>} aPoints The points in the first polygon.
* @param {Array.<Vector>} bPoints The points in the second polygon.
* @param {Vector} axis The axis (unit sized) to test against. The points of both polygons
* will be projected onto this axis.
* @param {Response=} response A Response object (optional) which will be populated
* if the axis is not a separating axis.
* @return {boolean} true if it is a separating axis, false otherwise. If false,
* and a response is passed in, information about how much overlap and
* the direction of the overlap will be populated.
*/
function isSeparatingAxis(aPos, bPos, aPoints, bPoints, axis, response) {
var rangeA = T_ARRAYS.pop();
var rangeB = T_ARRAYS.pop();
// The magnitude of the offset between the two polygons
var offsetV = T_VECTORS.pop().copy(bPos).sub(aPos);
var projectedOffset = offsetV.dot(axis);
// Project the polygons onto the axis.
flattenPointsOn(aPoints, axis, rangeA);
flattenPointsOn(bPoints, axis, rangeB);
// Move B's range to its position relative to A.
rangeB[0] += projectedOffset;
rangeB[1] += projectedOffset;
// Check if there is a gap. If there is, this is a separating axis and we can stop
if (rangeA[0] > rangeB[1] || rangeB[0] > rangeA[1]) {
T_VECTORS.push(offsetV);
T_ARRAYS.push(rangeA);
T_ARRAYS.push(rangeB);
return true;
}
// This is not a separating axis. If we're calculating a response, calculate the overlap.
if (response) {
var overlap = 0;
// A starts further left than B
if (rangeA[0] < rangeB[0]) {
response['aInB'] = false;
// A ends before B does. We have to pull A out of B
if (rangeA[1] < rangeB[1]) {
overlap = rangeA[1] - rangeB[0];
response['bInA'] = false;
// B is fully inside A. Pick the shortest way out.
} else {
var option1 = rangeA[1] - rangeB[0];
var option2 = rangeB[1] - rangeA[0];
overlap = option1 < option2 ? option1 : -option2;
}
// B starts further left than A
} else {
response['bInA'] = false;
// B ends before A ends. We have to push A out of B
if (rangeA[1] > rangeB[1]) {
overlap = rangeA[0] - rangeB[1];
response['aInB'] = false;
// A is fully inside B. Pick the shortest way out.
} else {
var option1 = rangeA[1] - rangeB[0];
var option2 = rangeB[1] - rangeA[0];
overlap = option1 < option2 ? option1 : -option2;
}
}
// If this is the smallest amount of overlap we've seen so far, set it as the minimum overlap.
var absOverlap = Math.abs(overlap);
if (absOverlap < response['overlap']) {
response['overlap'] = absOverlap;
response['overlapN'].copy(axis);
if (overlap < 0) {
response['overlapN'].reverse();
}
}
}
T_VECTORS.push(offsetV);
T_ARRAYS.push(rangeA);
T_ARRAYS.push(rangeB);
return false;
}
// Calculates which Vornoi region a point is on a line segment.
// It is assumed that both the line and the point are relative to `(0,0)`
//
// | (0) |
// (-1) [S]--------------[E] (1)
// | (0) |
/**
* @param {Vector} line The line segment.
* @param {Vector} point The point.
* @return {number} LEFT_VORNOI_REGION (-1) if it is the left region,
* MIDDLE_VORNOI_REGION (0) if it is the middle region,
* RIGHT_VORNOI_REGION (1) if it is the right region.
*/
function vornoiRegion(line, point) {
var len2 = line.len2();
var dp = point.dot(line);
// If the point is beyond the start of the line, it is in the
// left vornoi region.
if (dp < 0) { return LEFT_VORNOI_REGION; }
// If the point is beyond the end of the line, it is in the
// right vornoi region.
else if (dp > len2) { return RIGHT_VORNOI_REGION; }
// Otherwise, it's in the middle one.
else { return MIDDLE_VORNOI_REGION; }
}
// Constants for Vornoi regions
/**
* @const
*/
var LEFT_VORNOI_REGION = -1;
/**
* @const
*/
var MIDDLE_VORNOI_REGION = 0;
/**
* @const
*/
var RIGHT_VORNOI_REGION = 1;
// ## Collision Tests
// Check if two circles collide.
/**
* @param {Circle} a The first circle.
* @param {Circle} b The second circle.
* @param {Response=} response Response object (optional) that will be populated if
* the circles intersect.
* @return {boolean} true if the circles intersect, false if they don't.
*/
function testCircleCircle(a, b, response) {
// Check if the distance between the centers of the two
// circles is greater than their combined radius.
var differenceV = T_VECTORS.pop().copy(b['pos']).sub(a['pos']);
var totalRadius = a['r'] + b['r'];
var totalRadiusSq = totalRadius * totalRadius;
var distanceSq = differenceV.len2();
// If the distance is bigger than the combined radius, they don't intersect.
if (distanceSq > totalRadiusSq) {
T_VECTORS.push(differenceV);
return false;
}
// They intersect. If we're calculating a response, calculate the overlap.
if (response) {
var dist = Math.sqrt(distanceSq);
response['a'] = a;
response['b'] = b;
response['overlap'] = totalRadius - dist;
response['overlapN'].copy(differenceV.normalize());
response['overlapV'].copy(differenceV).scale(response['overlap']);
response['aInB']= a['r'] <= b['r'] && dist <= b['r'] - a['r'];
response['bInA'] = b['r'] <= a['r'] && dist <= a['r'] - b['r'];
}
T_VECTORS.push(differenceV);
return true;
}
SAT['testCircleCircle'] = testCircleCircle;
// Check if a polygon and a circle collide.
/**
* @param {Polygon} polygon The polygon.
* @param {Circle} circle The circle.
* @param {Response=} response Response object (optional) that will be populated if
* they interset.
* @return {boolean} true if they intersect, false if they don't.
*/
function testPolygonCircle(polygon, circle, response) {
// Get the position of the circle relative to the polygon.
var circlePos = T_VECTORS.pop().copy(circle['pos']).sub(polygon['pos']);
var radius = circle['r'];
var radius2 = radius * radius;
var points = polygon['points'];
var len = points.length;
var edge = T_VECTORS.pop();
var point = T_VECTORS.pop();
// For each edge in the polygon:
for (var i = 0; i < len; i++) {
var next = i === len - 1 ? 0 : i + 1;
var prev = i === 0 ? len - 1 : i - 1;
var overlap = 0;
var overlapN = null;
// Get the edge.
edge.copy(polygon['edges'][i]);
// Calculate the center of the circle relative to the starting point of the edge.
point.copy(circlePos).sub(points[i]);
// If the distance between the center of the circle and the point
// is bigger than the radius, the polygon is definitely not fully in
// the circle.
if (response && point.len2() > radius2) {
response['aInB'] = false;
}
// Calculate which Vornoi region the center of the circle is in.
var region = vornoiRegion(edge, point);
// If it's the left region:
if (region === LEFT_VORNOI_REGION) {
// We need to make sure we're in the RIGHT_VORNOI_REGION of the previous edge.
edge.copy(polygon['edges'][prev]);
// Calculate the center of the circle relative the starting point of the previous edge
var point2 = T_VECTORS.pop().copy(circlePos).sub(points[prev]);
region = vornoiRegion(edge, point2);
if (region === RIGHT_VORNOI_REGION) {
// It's in the region we want. Check if the circle intersects the point.
var dist = point.len();
if (dist > radius) {
// No intersection
T_VECTORS.push(circlePos);
T_VECTORS.push(edge);
T_VECTORS.push(point);
T_VECTORS.push(point2);
return false;
} else if (response) {
// It intersects, calculate the overlap.
response['bInA'] = false;
overlapN = point.normalize();
overlap = radius - dist;
}
}
T_VECTORS.push(point2);
// If it's the right region:
} else if (region === RIGHT_VORNOI_REGION) {
// We need to make sure we're in the left region on the next edge
edge.copy(polygon['edges'][next]);
// Calculate the center of the circle relative to the starting point of the next edge.
point.copy(circlePos).sub(points[next]);
region = vornoiRegion(edge, point);
if (region === LEFT_VORNOI_REGION) {
// It's in the region we want. Check if the circle intersects the point.
var dist = point.len();
if (dist > radius) {
// No intersection
T_VECTORS.push(circlePos);
T_VECTORS.push(edge);
T_VECTORS.push(point);
return false;
} else if (response) {
// It intersects, calculate the overlap.
response['bInA'] = false;
overlapN = point.normalize();
overlap = radius - dist;
}
}
// Otherwise, it's the middle region:
} else {
// Need to check if the circle is intersecting the edge,
// Change the edge into its "edge normal".
var normal = edge.perp().normalize();
// Find the perpendicular distance between the center of the
// circle and the edge.
var dist = point.dot(normal);
var distAbs = Math.abs(dist);
// If the circle is on the outside of the edge, there is no intersection.
if (dist > 0 && distAbs > radius) {
// No intersection
T_VECTORS.push(circlePos);
T_VECTORS.push(normal);
T_VECTORS.push(point);
return false;
} else if (response) {
// It intersects, calculate the overlap.
overlapN = normal;
overlap = radius - dist;
// If the center of the circle is on the outside of the edge, or part of the
// circle is on the outside, the circle is not fully inside the polygon.
if (dist >= 0 || overlap < 2 * radius) {
response['bInA'] = false;
}
}
}
// If this is the smallest overlap we've seen, keep it.
// (overlapN may be null if the circle was in the wrong Vornoi region).
if (overlapN && response && Math.abs(overlap) < Math.abs(response['overlap'])) {
response['overlap'] = overlap;
response['overlapN'].copy(overlapN);
}
}
// Calculate the final overlap vector - based on the smallest overlap.
if (response) {
response['a'] = polygon;
response['b'] = circle;
response['overlapV'].copy(response['overlapN']).scale(response['overlap']);
}
T_VECTORS.push(circlePos);
T_VECTORS.push(edge);
T_VECTORS.push(point);
return true;
}
SAT['testPolygonCircle'] = testPolygonCircle;
// Check if a circle and a polygon collide.
//
// **NOTE:** This is slightly less efficient than polygonCircle as it just
// runs polygonCircle and reverses everything at the end.
/**
* @param {Circle} circle The circle.
* @param {Polygon} polygon The polygon.
* @param {Response=} response Response object (optional) that will be populated if
* they interset.
* @return {boolean} true if they intersect, false if they don't.
*/
function testCirclePolygon(circle, polygon, response) {
// Test the polygon against the circle.
var result = testPolygonCircle(polygon, circle, response);
if (result && response) {
// Swap A and B in the response.
var a = response['a'];
var aInB = response['aInB'];
response['overlapN'].reverse();
response['overlapV'].reverse();
response['a'] = response['b'];
response['b'] = a;
response['aInB'] = response['bInA'];
response['bInA'] = aInB;
}
return result;
}
SAT['testCirclePolygon'] = testCirclePolygon;
// Checks whether polygons collide.
/**
* @param {Polygon} a The first polygon.
* @param {Polygon} b The second polygon.
* @param {Response=} response Response object (optional) that will be populated if
* they interset.
* @return {boolean} true if they intersect, false if they don't.
*/
function testPolygonPolygon(a, b, response) {
var aPoints = a['points'];
var aLen = aPoints.length;
var bPoints = b['points'];
var bLen = bPoints.length;
// If any of the edge normals of A is a separating axis, no intersection.
for (var i = 0; i < aLen; i++) {
if (isSeparatingAxis(a['pos'], b['pos'], aPoints, bPoints, a['normals'][i], response)) {
return false;
}
}
// If any of the edge normals of B is a separating axis, no intersection.
for (var i = 0;i < bLen; i++) {
if (isSeparatingAxis(a['pos'], b['pos'], aPoints, bPoints, b['normals'][i], response)) {
return false;
}
}
// Since none of the edge normals of A or B are a separating axis, there is an intersection
// and we've already calculated the smallest overlap (in isSeparatingAxis). Calculate the
// final overlap vector.
if (response) {
response['a'] = a;
response['b'] = b;
response['overlapV'].copy(response['overlapN']).scale(response['overlap']);
}
return true;
}
SAT['testPolygonPolygon'] = testPolygonPolygon;
return SAT;
})();