cannon/src/utils/Octree.js

A lightweight 3D physics engine written in JavaScript.

var AABB = require('../collision/AABB');
var Vec3 = require('../math/Vec3');

module.exports = Octree;

/**
 * @class OctreeNode
 * @param {object} [options]
 * @param {Octree} [options.root]
 * @param {AABB} [options.aabb]
 */
function OctreeNode(options){
    options = options || {};

    /**
     * The root node
     * @property {OctreeNode} root
     */
    this.root = options.root || null;

    /**
     * Boundary of this node
     * @property {AABB} aabb
     */
    this.aabb = options.aabb ? options.aabb.clone() : new AABB();

    /**
     * Contained data at the current node level.
     * @property {Array} data
     */
    this.data = [];

    /**
     * Children to this node
     * @property {Array} children
     */
    this.children = [];
}

/**
 * @class Octree
 * @param {AABB} aabb The total AABB of the tree
 * @param {object} [options]
 * @param {number} [options.maxDepth=8]
 * @extends OctreeNode
 */
function Octree(aabb, options){
    options = options || {};
    options.root = null;
    options.aabb = aabb;
    OctreeNode.call(this, options);

    /**
     * Maximum subdivision depth
     * @property {number} maxDepth
     */
    this.maxDepth = typeof(options.maxDepth) !== 'undefined' ? options.maxDepth : 8;
}
Octree.prototype = new OctreeNode();

OctreeNode.prototype.reset = function(aabb, options){
    this.children.length = this.data.length = 0;
};

/**
 * Insert data into this node
 * @method insert
 * @param  {AABB} aabb
 * @param  {object} elementData
 * @return {boolean} True if successful, otherwise false
 */
OctreeNode.prototype.insert = function(aabb, elementData, level){
    var nodeData = this.data;
    level = level || 0;

    // Ignore objects that do not belong in this node
    if (!this.aabb.contains(aabb)){
        return false; // object cannot be added
    }

    var children = this.children;

    if(level < (this.maxDepth || this.root.maxDepth)){
        // Subdivide if there are no children yet
        var subdivided = false;
        if (!children.length){
            this.subdivide();
            subdivided = true;
        }

        // add to whichever node will accept it
        for (var i = 0; i !== 8; i++) {
            if (children[i].insert(aabb, elementData, level + 1)){
                return true;
            }
        }

        if(subdivided){
            // No children accepted! Might as well just remove em since they contain none
            children.length = 0;
        }
    }

    // Too deep, or children didnt want it. add it in current node
    nodeData.push(elementData);

    return true;
};

var halfDiagonal = new Vec3();

/**
 * Create 8 equally sized children nodes and put them in the .children array.
 * @method subdivide
 */
OctreeNode.prototype.subdivide = function() {
    var aabb = this.aabb;
    var l = aabb.lowerBound;
    var u = aabb.upperBound;

    var children = this.children;

    children.push(
        new OctreeNode({ aabb: new AABB({ lowerBound: new Vec3(0,0,0) }) }),
        new OctreeNode({ aabb: new AABB({ lowerBound: new Vec3(1,0,0) }) }),
        new OctreeNode({ aabb: new AABB({ lowerBound: new Vec3(1,1,0) }) }),
        new OctreeNode({ aabb: new AABB({ lowerBound: new Vec3(1,1,1) }) }),
        new OctreeNode({ aabb: new AABB({ lowerBound: new Vec3(0,1,1) }) }),
        new OctreeNode({ aabb: new AABB({ lowerBound: new Vec3(0,0,1) }) }),
        new OctreeNode({ aabb: new AABB({ lowerBound: new Vec3(1,0,1) }) }),
        new OctreeNode({ aabb: new AABB({ lowerBound: new Vec3(0,1,0) }) })
    );

    u.vsub(l, halfDiagonal);
    halfDiagonal.scale(0.5, halfDiagonal);

    var root = this.root || this;

    for (var i = 0; i !== 8; i++) {
        var child = children[i];

        // Set current node as root
        child.root = root;

        // Compute bounds
        var lowerBound = child.aabb.lowerBound;
        lowerBound.x *= halfDiagonal.x;
        lowerBound.y *= halfDiagonal.y;
        lowerBound.z *= halfDiagonal.z;

        lowerBound.vadd(l, lowerBound);

        // Upper bound is always lower bound + halfDiagonal
        lowerBound.vadd(halfDiagonal, child.aabb.upperBound);
    }
};

/**
 * Get all data, potentially within an AABB
 * @method aabbQuery
 * @param  {AABB} aabb
 * @param  {array} result
 * @return {array} The "result" object
 */
OctreeNode.prototype.aabbQuery = function(aabb, result) {

    var nodeData = this.data;

    // abort if the range does not intersect this node
    // if (!this.aabb.overlaps(aabb)){
    //     return result;
    // }

    // Add objects at this level
    // Array.prototype.push.apply(result, nodeData);

    // Add child data
    // @todo unwrap recursion into a queue / loop, that's faster in JS
    var children = this.children;


    // for (var i = 0, N = this.children.length; i !== N; i++) {
    //     children[i].aabbQuery(aabb, result);
    // }

    var queue = [this];
    while (queue.length) {
        var node = queue.pop();
        if (node.aabb.overlaps(aabb)){
            Array.prototype.push.apply(result, node.data);
        }
        Array.prototype.push.apply(queue, node.children);
    }

    return result;
};

var tmpAABB = new AABB();

/**
 * Get all data, potentially intersected by a ray.
 * @method rayQuery
 * @param  {Ray} ray
 * @param  {Transform} treeTransform
 * @param  {array} result
 * @return {array} The "result" object
 */
OctreeNode.prototype.rayQuery = function(ray, treeTransform, result) {

    // Use aabb query for now.
    // @todo implement real ray query which needs less lookups
    ray.getAABB(tmpAABB);
    tmpAABB.toLocalFrame(treeTransform, tmpAABB);
    this.aabbQuery(tmpAABB, result);

    return result;
};

/**
 * @method removeEmptyNodes
 */
OctreeNode.prototype.removeEmptyNodes = function() {
    var queue = [this];
    while (queue.length) {
        var node = queue.pop();
        for (var i = node.children.length - 1; i >= 0; i--) {
            if(!node.children[i].data.length){
                node.children.splice(i, 1);
            }
        }
        Array.prototype.push.apply(queue, node.children);
    }
};