p2s
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A JavaScript 2D physics engine.
212 lines (188 loc) • 6.43 kB
JavaScript
var Shape = require('./Shape')
, vec2 = require('../math/vec2')
, shallowClone = require('../utils/Utils').shallowClone;
module.exports = Heightfield;
/**
* Heightfield shape class. Height data is given as an array. These data points are spread out evenly with a distance "elementWidth".
* @class Heightfield
* @extends Shape
* @constructor
* @param {object} [options] (Note that this options object will be passed on to the {{#crossLink "Shape"}}{{/crossLink}} constructor.)
* @param {array} [options.heights] An array of Y values that will be used to construct the terrain.
* @param {Number} [options.minValue] Minimum value of the data points in the data array. Will be computed automatically if not given.
* @param {Number} [options.maxValue] Maximum value.
* @param {Number} [options.elementWidth=0.1] World spacing between the data points in X direction.
*
* @example
* // Generate some height data (y-values).
* var heights = [];
* for(var i = 0; i < 1000; i++){
* var y = 0.5 * Math.cos(0.2 * i);
* heights.push(y);
* }
*
* // Create the heightfield shape
* var shape = new Heightfield({
* heights: heights,
* elementWidth: 1 // Distance between the data points in X direction
* });
* var body = new Body();
* body.addShape(shape);
* world.addBody(body);
*
* @todo Should use a scale property with X and Y direction instead of just elementWidth
*/
function Heightfield(options){
options = options ? shallowClone(options) : {};
/**
* An array of numbers, or height values, that are spread out along the x axis.
* @property {array} heights
*/
this.heights = options.heights ? options.heights.slice(0) : [];
/**
* Max value of the heights
* @property {number} maxValue
*/
this.maxValue = options.maxValue || null;
/**
* Max value of the heights
* @property {number} minValue
*/
this.minValue = options.minValue || null;
/**
* The width of each element
* @property {number} elementWidth
*/
this.elementWidth = options.elementWidth !== undefined ? options.elementWidth : 0.1;
if(options.maxValue === undefined || options.minValue === undefined){
this.updateMaxMinValues();
}
options.type = Shape.HEIGHTFIELD;
Shape.call(this, options);
}
Heightfield.prototype = new Shape();
Heightfield.prototype.constructor = Heightfield;
/**
* Update the .minValue and the .maxValue
* @method updateMaxMinValues
*/
Heightfield.prototype.updateMaxMinValues = function(){
var data = this.heights;
var maxValue = data[0];
var minValue = data[0];
for(var i=0; i !== data.length; i++){
var v = data[i];
if(v > maxValue){
maxValue = v;
}
if(v < minValue){
minValue = v;
}
}
this.maxValue = maxValue;
this.minValue = minValue;
};
/**
* @method computeMomentOfInertia
* @return {Number}
*/
Heightfield.prototype.computeMomentOfInertia = function(){
return Number.MAX_VALUE;
};
Heightfield.prototype.updateBoundingRadius = function(){
this.boundingRadius = Number.MAX_VALUE;
};
Heightfield.prototype.updateArea = function(){
var data = this.heights,
area = 0;
for(var i=0; i<data.length-1; i++){
area += (data[i]+data[i+1]) / 2 * this.elementWidth;
}
this.area = area;
};
var points = [
vec2.create(),
vec2.create(),
vec2.create(),
vec2.create()
];
/**
* @method computeAABB
* @param {AABB} out The resulting AABB.
* @param {Array} position
* @param {Number} angle
*/
Heightfield.prototype.computeAABB = function(out, position, angle){
vec2.set(points[0], 0, this.maxValue);
vec2.set(points[1], this.elementWidth * this.heights.length, this.maxValue);
vec2.set(points[2], this.elementWidth * this.heights.length, this.minValue);
vec2.set(points[3], 0, this.minValue);
out.setFromPoints(points, position, angle);
};
/**
* Get a line segment in the heightfield
* @method getLineSegment
* @param {array} start Where to store the resulting start point
* @param {array} end Where to store the resulting end point
* @param {number} i
*/
Heightfield.prototype.getLineSegment = function(start, end, i){
var data = this.heights;
var width = this.elementWidth;
vec2.set(start, i * width, data[i]);
vec2.set(end, (i + 1) * width, data[i + 1]);
};
Heightfield.prototype.getSegmentIndex = function(position){
return Math.floor(position[0] / this.elementWidth);
};
Heightfield.prototype.getClampedSegmentIndex = function(position){
var i = this.getSegmentIndex(position);
i = Math.min(this.heights.length, Math.max(i, 0)); // clamp
return i;
};
var intersectHeightfield_worldNormal = vec2.create();
var intersectHeightfield_l0 = vec2.create();
var intersectHeightfield_l1 = vec2.create();
var intersectHeightfield_localFrom = vec2.create();
var intersectHeightfield_localTo = vec2.create();
/**
* @method raycast
* @param {RayResult} result
* @param {Ray} ray
* @param {array} position
* @param {number} angle
*/
Heightfield.prototype.raycast = function(result, ray, position, angle){
var from = ray.from;
var to = ray.to;
var worldNormal = intersectHeightfield_worldNormal;
var l0 = intersectHeightfield_l0;
var l1 = intersectHeightfield_l1;
var localFrom = intersectHeightfield_localFrom;
var localTo = intersectHeightfield_localTo;
// get local ray start and end
vec2.toLocalFrame(localFrom, from, position, angle);
vec2.toLocalFrame(localTo, to, position, angle);
// Get the segment range
var i0 = this.getClampedSegmentIndex(localFrom);
var i1 = this.getClampedSegmentIndex(localTo);
if(i0 > i1){
var tmp = i0;
i0 = i1;
i1 = tmp;
}
// The segments
for(var i=0; i<this.heights.length - 1; i++){
this.getLineSegment(l0, l1, i);
var t = vec2.getLineSegmentsIntersectionFraction(localFrom, localTo, l0, l1);
if(t >= 0){
vec2.subtract(worldNormal, l1, l0);
vec2.rotate(worldNormal, worldNormal, angle + Math.PI / 2);
vec2.normalize(worldNormal, worldNormal);
ray.reportIntersection(result, t, worldNormal, -1);
if(result.shouldStop(ray)){
return;
}
}
}
};