p2s/src/utils/OverlapKeeper.js

A JavaScript 2D physics engine.

var TupleDictionary = require('./TupleDictionary');
var OverlapKeeperRecordPool = require('./OverlapKeeperRecordPool');

module.exports = OverlapKeeper;

/**
 * Keeps track of overlaps in the current state and the last step state.
 * @class OverlapKeeper
 * @constructor
 */
function OverlapKeeper() {
    this.overlappingShapesLastState = new TupleDictionary();
    this.overlappingShapesCurrentState = new TupleDictionary();
    this.recordPool = new OverlapKeeperRecordPool({ size: 16 });
    this.tmpDict = new TupleDictionary();
    this.tmpArray1 = [];
}

/**
 * Ticks one step forward in time. This will move the current overlap state to the "old" overlap state, and create a new one as current.
 * @method tick
 */
OverlapKeeper.prototype.tick = function() {
    var last = this.overlappingShapesLastState;
    var current = this.overlappingShapesCurrentState;

    // Save old objects into pool
    var l = last.keys.length;
    while(l--){
        var key = last.keys[l];
        var lastObject = last.getByKey(key);
        if(lastObject){
            // The record is only used in the "last" dict, and will be removed. We might as well pool it.
            this.recordPool.release(lastObject);
        }
    }

    // Clear last object
    last.reset();

    // Transfer from new object to old
    last.copy(current);

    // Clear current object
    current.reset();
};

/**
 * @method setOverlapping
 * @param {Body} bodyA
 * @param {Body} shapeA
 * @param {Body} bodyB
 * @param {Body} shapeB
 */
OverlapKeeper.prototype.setOverlapping = function(bodyA, shapeA, bodyB, shapeB) {
    var current = this.overlappingShapesCurrentState;

    // Store current contact state
    if(!current.get(shapeA.id, shapeB.id)){
        var data = this.recordPool.get();
        data.set(bodyA, shapeA, bodyB, shapeB);
        current.set(shapeA.id, shapeB.id, data);
    }
};

OverlapKeeper.prototype.getNewOverlaps = function(result){
    return this.getDiff(this.overlappingShapesLastState, this.overlappingShapesCurrentState, result);
};

OverlapKeeper.prototype.getEndOverlaps = function(result){
    return this.getDiff(this.overlappingShapesCurrentState, this.overlappingShapesLastState, result);
};

/**
 * Checks if two bodies are currently overlapping.
 * @method bodiesAreOverlapping
 * @param  {Body} bodyA
 * @param  {Body} bodyB
 * @return {boolean}
 */
OverlapKeeper.prototype.bodiesAreOverlapping = function(bodyA, bodyB){
    var current = this.overlappingShapesCurrentState;
    var l = current.keys.length;
    while(l--){
        var key = current.keys[l];
        var data = current.data[key];
        if((data.bodyA === bodyA && data.bodyB === bodyB) || data.bodyA === bodyB && data.bodyB === bodyA){
            return true;
        }
    }
    return false;
};

OverlapKeeper.prototype.getDiff = function(dictA, dictB, result){
    var result = result || [];
    var last = dictA;
    var current = dictB;

    result.length = 0;

    var l = current.keys.length;
    while(l--){
        var key = current.keys[l];
        var data = current.data[key];

        if(!data){
            throw new Error('Key '+key+' had no data!');
        }

        var lastData = last.data[key];
        if(!lastData){
            // Not overlapping in last state, but in current.
            result.push(data);
        }
    }

    return result;
};

OverlapKeeper.prototype.isNewOverlap = function(shapeA, shapeB){
    var idA = shapeA.id|0,
        idB = shapeB.id|0;
    var last = this.overlappingShapesLastState;
    var current = this.overlappingShapesCurrentState;
    // Not in last but in new
    return !!!last.get(idA, idB) && !!current.get(idA, idB);
};

OverlapKeeper.prototype.getNewBodyOverlaps = function(result){
    this.tmpArray1.length = 0;
    var overlaps = this.getNewOverlaps(this.tmpArray1);
    return this.getBodyDiff(overlaps, result);
};

OverlapKeeper.prototype.getEndBodyOverlaps = function(result){
    this.tmpArray1.length = 0;
    var overlaps = this.getEndOverlaps(this.tmpArray1);
    return this.getBodyDiff(overlaps, result);
};

OverlapKeeper.prototype.getBodyDiff = function(overlaps, result){
    result = result || [];
    var accumulator = this.tmpDict;

    var l = overlaps.length;

    while(l--){
        var data = overlaps[l];

        // Since we use body id's for the accumulator, these will be a subset of the original one
        accumulator.set(data.bodyA.id|0, data.bodyB.id|0, data);
    }

    l = accumulator.keys.length;
    while(l--){
        var data = accumulator.getByKey(accumulator.keys[l]);
        if(data){
            result.push(data.bodyA, data.bodyB);
        }
    }

    accumulator.reset();

    return result;
};