Babylon.js/src/Tools/babylon.rectPackingMap.ts

module BABYLON {
    /**
     * The purpose of this class is to pack several Rectangles into a big map, while trying to fit everything as optimaly as possible.
     * This class is typically used to build lightmaps, sprite map or to pack several little textures into a big one.
     * Note that this class allows allocated Rectangles to be freed: that is the map is dynamically maintained so you can add/remove rectangle based on their lifecycle.
     */
    export class RectPackingMap extends PackedRect {
        /**
         * Create an instance of the object with a dimension using the given size
         * @param size The dimension of the rectangle that will contain all the sub ones.
         */
        constructor(size: Size) {
            super(null, null, Vector2.Zero(), size);

            this._root = this;
        }

        /**
         * Add a rectangle, finding the best location to store it into the map
         * @param size the dimension of the rectangle to store
         * @return the Node containing the rectangle information, or null if we couldn't find a free spot
         */
        public addRect(size: Size): PackedRect {
            var node = this.findAndSplitNode(size);
            return node;
        }

        /**
         * Return the current space free normalized between [0;1]
         * @returns {} 
         */
        public get freeSpace(): number {
            var freeSize = 0;
            freeSize = this.evalFreeSize(freeSize);

            return freeSize / (this._size.width * this._size.height);
        }
    }

    /**
     * This class describe a rectangle that were added to the map.
     * You have access to its coordinates either in pixel or normalized (UV)
     */
    export class PackedRect {
        constructor(root: PackedRect, parent: PackedRect, pos: Vector2, size: Size) {
            this._pos = pos;
            this._size = size;
            this._root = root;
            this._parent = parent;
        }

        /**
         * @returns the position of this node into the map
         */
        public get pos() {
            return this._pos;
        }

        /**
         * @returns the size of the rectangle this node handles
         */
        public get contentSize(): Size {
            return this._contentSize;
        }

        /**
         * Compute the UV of the top/left, top/right, bottom/right, bottom/left points of the rectangle this node handles into the map
         * @returns And array of 4 Vector2, containing UV coordinates for the four corners of the Rectangle into the map
         */
        public get UVs(): Vector2[] {
            var mainWidth = this._root._size.width;
            var mainHeight = this._root._size.height;

            var topLeft = new Vector2(this._pos.x / mainWidth, this._pos.y / mainHeight);
            var rightBottom = new Vector2((this._pos.x + this._contentSize.width - 1) / mainWidth, (this._pos.y + this._contentSize.height - 1) / mainHeight);
            var uvs = new Array<Vector2>();
            uvs.push(topLeft);
            uvs.push(new Vector2(rightBottom.x, topLeft.y));
            uvs.push(rightBottom);
            uvs.push(new Vector2(topLeft.x, rightBottom.y));

            return uvs;
        }

        /**
         * Free this rectangle from the map.
         * Call this method when you no longer need the rectangle to be in the map.
         */
        public freeContent() {
            if (!this.contentSize) {
                return;
            }

            this._contentSize = null;

            // If everything below is also free, reset the whole node, and attempt to reset parents if they also become free
            this.attemptDefrag();
        }


        protected get isUsed(): boolean {
            return this._contentSize != null || this._leftNode != null;
        }

        protected findAndSplitNode(contentSize: Size): PackedRect {
            var node = this.findNode(contentSize);

            // Not enought space...
            if (!node) {
                return null;
            }

            node.splitNode(contentSize);
            return node;
        }

        private findNode(size: Size): PackedRect {
            var resNode: PackedRect = null;

            // If this node is used, recurse to each of his subNodes to find an available one in its branch
            if (this.isUsed) {
                if (this._leftNode) {
                    resNode = this._leftNode.findNode(size);
                }
                if (!resNode && this._rightNode) {
                    resNode = this._rightNode.findNode(size);
                }
                if (!resNode && this._bottomNode) {
                    resNode = this._bottomNode.findNode(size);
                }
            }

            // The node is free, but was previously allocated (_initialSize is set), rely on initialSize to make the test as it's the space we have
            else if (this._initialSize && (size.width <= this._initialSize.width) && (size.height <= this._initialSize.height)) {
                resNode = this;
            }

            // The node is free and empty, rely on its size for the test
            else if ((size.width <= this._size.width) && (size.height <= this._size.height)) {
                resNode = this;
            }
            return resNode;
        }

        private splitNode(contentSize: Size): PackedRect {
            // If there's no contentSize but an initialSize it means this node were previously allocated, but freed, we need to create a _leftNode as subNode and use to allocate the space we need (and this node will have a right/bottom subNode for the space left as this._initialSize may be greater than contentSize)
            if (!this._contentSize && this._initialSize) {
                this._leftNode = new PackedRect(this._root, this, new Vector2(this._pos.x, this._pos.y), new Size(this._initialSize.width, this._initialSize.height));
                return this._leftNode.splitNode(contentSize);
            } else {
                this._contentSize = contentSize.clone();
                this._initialSize = contentSize.clone();

                if (contentSize.width !== this._size.width) {
                    this._rightNode = new PackedRect(this._root, this, new Vector2(this._pos.x + contentSize.width, this._pos.y), new Size(this._size.width - contentSize.width, contentSize.height));
                }

                if (contentSize.height !== this._size.height) {
                    this._bottomNode = new PackedRect(this._root, this, new Vector2(this._pos.x, this._pos.y + contentSize.height), new Size(this._size.width, this._size.height - contentSize.height));
                }
                return this;
            }
        }

        private attemptDefrag() {
            if (!this.isUsed && this.isRecursiveFree) {
                this.clearNode();

                if (this._parent) {
                    this._parent.attemptDefrag();
                }
            }
        }

        private clearNode() {
            this._initialSize = null;
            this._rightNode = null;
            this._bottomNode = null;
        }

        private get isRecursiveFree() {
            return !this.contentSize && (!this._leftNode || this._leftNode.isRecursiveFree) && (!this._rightNode || this._rightNode.isRecursiveFree) && (!this._bottomNode || this._bottomNode.isRecursiveFree);
        }

        protected evalFreeSize(size: number): number {
            var levelSize = 0;

            if (!this.isUsed) {
                if (this._initialSize) {
                    levelSize = this._initialSize.surface;
                } else {
                    levelSize = this._size.surface;
                }
            }

            if (this._rightNode) {
                levelSize += this._rightNode.evalFreeSize(0);
            }

            if (this._bottomNode) {
                levelSize += this._bottomNode.evalFreeSize(0);
            }

            return levelSize + size;
        }

        protected _root: PackedRect;
        protected _parent: PackedRect;
        private _contentSize: Size;
        private _initialSize: Size;
        private _leftNode: PackedRect;
        private _rightNode: PackedRect;
        private _bottomNode: PackedRect;

        private _pos: Vector2;
        protected _size: Size;
    }


}