lance-gg/src/physics/SimplePhysics/HSHG.ts

A Node.js based real-time multiplayer game server

// Hierarchical Spatial Hash Grid: HSHG
// source: https://gist.github.com/kirbysayshi/1760774

// ---------------------------------------------------------------------
// GLOBAL FUNCTIONS
// ---------------------------------------------------------------------

/**
 * Updates every object's position in the grid, but only if
 * the hash value for that object has changed.
 * This method DOES NOT take into account object expansion or
 * contraction, just position, and does not attempt to change
 * the grid the object is currently in; it only (possibly) changes
 * the cell.
 *
 * If the object has significantly changed in size, the best bet is to
 * call removeObject() and addObject() sequentially, outside of the
 * normal update cycle of HSHG.
 *
 * @return  void   desc
 */
function update_RECOMPUTE() {

    var i,
        obj,
        grid,
        meta,
        objAABB,
        newObjHash;

    // for each object
    for (i = 0; i < this._globalObjects.length; i++) {
        obj = this._globalObjects[i];
        meta = obj.HSHG;
        grid = meta.grid;

        // recompute hash
        objAABB = obj.getAABB();
        newObjHash = grid.toHash(objAABB.min[0], objAABB.min[1]);

        if (newObjHash !== meta.hash) {
            // grid position has changed, update!
            grid.removeObject(obj);
            grid.addObject(obj, newObjHash);
        }
    }
}

// not implemented yet :)
function update_REMOVEALL() {

}

function testAABBOverlap(objA, objB) {
    var a = objA.getAABB(),
        b = objB.getAABB();

    // if(a.min[0] > b.max[0] || a.min[1] > b.max[1] || a.min[2] > b.max[2]
    // || a.max[0] < b.min[0] || a.max[1] < b.min[1] || a.max[2] < b.min[2]){

    if (a.min[0] > b.max[0] || a.min[1] > b.max[1] ||
        a.max[0] < b.min[0] || a.max[1] < b.min[1]) {
        return false;
    }
    return true;

}

function getLongestAABBEdge(min, max) {
    return Math.max(
        Math.abs(max[0] - min[0])
        , Math.abs(max[1] - min[1])
        // ,Math.abs(max[2] - min[2])
    );
}

// ---------------------------------------------------------------------
// ENTITIES
// ---------------------------------------------------------------------

function HSHG() {

    this.MAX_OBJECT_CELL_DENSITY = 1 / 8; // objects / cells
    this.INITIAL_GRID_LENGTH = 256; // 16x16
    this.HIERARCHY_FACTOR = 2;
    this.HIERARCHY_FACTOR_SQRT = Math.SQRT2;
    this.UPDATE_METHOD = update_RECOMPUTE; // or update_REMOVEALL

    this._grids = [];
    this._globalObjects = [];
}

// HSHG.prototype.init = function(){
//	this._grids = [];
//	this._globalObjects = [];
// }

HSHG.prototype.addObject = function (obj) {
    var x, i,
        cellSize,
        objAABB = obj.getAABB(),
        objSize = getLongestAABBEdge(objAABB.min, objAABB.max),
        oneGrid, newGrid;

    // for HSHG metadata
    obj.HSHG = {
        globalObjectsIndex: this._globalObjects.length
    };

    // add to global object array
    this._globalObjects.push(obj);

    if (this._grids.length == 0) {
        // no grids exist yet
        cellSize = objSize * this.HIERARCHY_FACTOR_SQRT;
        newGrid = new Grid(cellSize, this.INITIAL_GRID_LENGTH, this);
        newGrid.initCells();
        newGrid.addObject(obj);

        this._grids.push(newGrid);
    } else {
        x = 0;

        // grids are sorted by cellSize, smallest to largest
        for (i = 0; i < this._grids.length; i++) {
            oneGrid = this._grids[i];
            x = oneGrid.cellSize;
            if (objSize < x) {
                x /= this.HIERARCHY_FACTOR;
                if (objSize < x) {
                    // find appropriate size
                    while (objSize < x) {
                        x /= this.HIERARCHY_FACTOR;
                    }
                    newGrid = new Grid(x * this.HIERARCHY_FACTOR, this.INITIAL_GRID_LENGTH, this);
                    newGrid.initCells();
                    // assign obj to grid
                    newGrid.addObject(obj);
                    // insert grid into list of grids directly before oneGrid
                    this._grids.splice(i, 0, newGrid);
                } else {
                    // insert obj into grid oneGrid
                    oneGrid.addObject(obj);
                }
                return;
            }
        }

        while (objSize >= x) {
            x *= this.HIERARCHY_FACTOR;
        }

        newGrid = new Grid(x, this.INITIAL_GRID_LENGTH, this);
        newGrid.initCells();
        // insert obj into grid
        newGrid.addObject(obj);
        // add newGrid as last element in grid list
        this._grids.push(newGrid);
    }
};

HSHG.prototype.removeObject = function (obj) {
    var meta = obj.HSHG,
        globalObjectsIndex,
        replacementObj;

    if (meta === undefined) {
        throw Error(obj + ' was not in the HSHG.');
        return;
    }

    // remove object from global object list
    globalObjectsIndex = meta.globalObjectsIndex;
    if (globalObjectsIndex === this._globalObjects.length - 1) {
        this._globalObjects.pop();
    } else {
        replacementObj = this._globalObjects.pop();
        replacementObj.HSHG.globalObjectsIndex = globalObjectsIndex;
        this._globalObjects[globalObjectsIndex] = replacementObj;
    }

    meta.grid.removeObject(obj);

    // remove meta data
    delete obj.HSHG;
};

HSHG.prototype.update = function () {
    this.UPDATE_METHOD.call(this);
};

HSHG.prototype.queryForCollisionPairs = function (broadOverlapTestCallback) {

    var i, j, k, l, c,
        grid,
        cell,
        objA,
        objB,
        offset,
        adjacentCell,
        biggerGrid,
        objAAABB,
        objAHashInBiggerGrid,
        possibleCollisions: any = [];

    // default broad test to internal aabb overlap test
    let broadOverlapTest = broadOverlapTestCallback || testAABBOverlap;

    // for all grids ordered by cell size ASC
    for (i = 0; i < this._grids.length; i++) {
        grid = this._grids[i];

        // for each cell of the grid that is occupied
        for (j = 0; j < grid.occupiedCells.length; j++) {
            cell = grid.occupiedCells[j];

            // collide all objects within the occupied cell
            for (k = 0; k < cell.objectContainer.length; k++) {
                objA = cell.objectContainer[k];
                for (l = k + 1; l < cell.objectContainer.length; l++) {
                    objB = cell.objectContainer[l];
                    if (broadOverlapTest(objA, objB) === true) {
                        possibleCollisions.push([objA, objB]);
                    }
                }
            }

            // for the first half of all adjacent cells (offset 4 is the current cell)
            for (c = 0; c < 4; c++) {
                offset = cell.neighborOffsetArray[c];

                // if(offset === null) { continue; }

                adjacentCell = grid.allCells[cell.allCellsIndex + offset];

                // collide all objects in cell with adjacent cell
                for (k = 0; k < cell.objectContainer.length; k++) {
                    objA = cell.objectContainer[k];
                    for (l = 0; l < adjacentCell.objectContainer.length; l++) {
                        objB = adjacentCell.objectContainer[l];
                        if (broadOverlapTest(objA, objB) === true) {
                            possibleCollisions.push([objA, objB]);
                        }
                    }
                }
            }
        }

        // forall objects that are stored in this grid
        for (j = 0; j < grid.allObjects.length; j++) {
            objA = grid.allObjects[j];
            objAAABB = objA.getAABB();

            // for all grids with cellsize larger than grid
            for (k = i + 1; k < this._grids.length; k++) {
                biggerGrid = this._grids[k];
                objAHashInBiggerGrid = biggerGrid.toHash(objAAABB.min[0], objAAABB.min[1]);
                cell = biggerGrid.allCells[objAHashInBiggerGrid];

                // check objA against every object in all cells in offset array of cell
                // for all adjacent cells...
                for (c = 0; c < cell.neighborOffsetArray.length; c++) {
                    offset = cell.neighborOffsetArray[c];

                    // if(offset === null) { continue; }

                    adjacentCell = biggerGrid.allCells[cell.allCellsIndex + offset];

                    // for all objects in the adjacent cell...
                    for (l = 0; l < adjacentCell.objectContainer.length; l++) {
                        objB = adjacentCell.objectContainer[l];
                        // test against object A
                        if (broadOverlapTest(objA, objB) === true) {
                            possibleCollisions.push([objA, objB]);
                        }
                    }
                }
            }
        }
    }

    // return list of object pairs
    return possibleCollisions;
};

HSHG.update_RECOMPUTE = update_RECOMPUTE;
HSHG.update_REMOVEALL = update_REMOVEALL;

/**
 * Grid
 *
 * @constructor
 * @param    int cellSize  the pixel size of each cell of the grid
 * @param    int cellCount  the total number of cells for the grid (width x height)
 * @param    HSHG parentHierarchy    the HSHG to which this grid belongs
 * @return  void
 */
function Grid(cellSize, cellCount, parentHierarchy) {
    this.cellSize = cellSize;
    this.inverseCellSize = 1 / cellSize;
    this.rowColumnCount = ~~Math.sqrt(cellCount);
    this.xyHashMask = this.rowColumnCount - 1;
    this.occupiedCells = [];
    this.allCells = Array(this.rowColumnCount * this.rowColumnCount);
    this.allObjects = [];
    this.sharedInnerOffsets = [];

    this._parentHierarchy = parentHierarchy || null;
}

Grid.prototype.initCells = function () {

    // TODO: inner/unique offset rows 0 and 2 may need to be
    // swapped due to +y being "down" vs "up"

    var i,
        gridLength = this.allCells.length,
        x, y,
        wh = this.rowColumnCount,
        isOnRightEdge, isOnLeftEdge, isOnTopEdge, isOnBottomEdge,
        innerOffsets = [
            // y+ down offsets
            // -1 + -wh, -wh, -wh + 1,
            // -1, 0, 1,
            // wh - 1, wh, wh + 1

            // y+ up offsets
            wh - 1, wh, wh + 1,
            -1, 0, 1,
            -1 + -wh, -wh, -wh + 1
        ],
        leftOffset, rightOffset, topOffset, bottomOffset,
        uniqueOffsets: any[] = [],
        cell;

    this.sharedInnerOffsets = innerOffsets;

    // init all cells, creating offset arrays as needed

    for (i = 0; i < gridLength; i++) {

        cell = new Cell();
        // compute row (y) and column (x) for an index
        y = ~~(i / this.rowColumnCount);
        x = ~~(i - (y * this.rowColumnCount));

        // reset / init
        isOnRightEdge = false;
        isOnLeftEdge = false;
        isOnTopEdge = false;
        isOnBottomEdge = false;

        // right or left edge cell
        if ((x + 1) % this.rowColumnCount == 0) {
            isOnRightEdge = true;
        } else if (x % this.rowColumnCount == 0) {
            isOnLeftEdge = true;
        }

        // top or bottom edge cell
        if ((y + 1) % this.rowColumnCount == 0) {
            isOnTopEdge = true;
        } else if (y % this.rowColumnCount == 0) {
            isOnBottomEdge = true;
        }

        // if cell is edge cell, use unique offsets, otherwise use inner offsets
        if (isOnRightEdge || isOnLeftEdge || isOnTopEdge || isOnBottomEdge) {

            // figure out cardinal offsets first
            rightOffset = isOnRightEdge === true ? -wh + 1 : 1;
            leftOffset = isOnLeftEdge === true ? wh - 1 : -1;
            topOffset = isOnTopEdge === true ? -gridLength + wh : wh;
            bottomOffset = isOnBottomEdge === true ? gridLength - wh : -wh;

            // diagonals are composites of the cardinals
            uniqueOffsets = [
                // y+ down offset
                // leftOffset + bottomOffset, bottomOffset, rightOffset + bottomOffset,
                // leftOffset, 0, rightOffset,
                // leftOffset + topOffset, topOffset, rightOffset + topOffset

                // y+ up offset
                leftOffset + topOffset, topOffset, rightOffset + topOffset,
                leftOffset, 0, rightOffset,
                leftOffset + bottomOffset, bottomOffset, rightOffset + bottomOffset
            ];

            cell.neighborOffsetArray = uniqueOffsets;
        } else {
            cell.neighborOffsetArray = this.sharedInnerOffsets;
        }

        cell.allCellsIndex = i;
        this.allCells[i] = cell;
    }
};

Grid.prototype.toHash = function (x, y, z) {
    var i, xHash, yHash, zHash;

    if (x < 0) {
        i = (-x) * this.inverseCellSize;
        xHash = this.rowColumnCount - 1 - (~~i & this.xyHashMask);
    } else {
        i = x * this.inverseCellSize;
        xHash = ~~i & this.xyHashMask;
    }

    if (y < 0) {
        i = (-y) * this.inverseCellSize;
        yHash = this.rowColumnCount - 1 - (~~i & this.xyHashMask);
    } else {
        i = y * this.inverseCellSize;
        yHash = ~~i & this.xyHashMask;
    }

    // if(z < 0){
    //	i = (-z) * this.inverseCellSize;
    //	zHash = this.rowColumnCount - 1 - ( ~~i & this.xyHashMask );
    // } else {
    //	i = z * this.inverseCellSize;
    //	zHash = ~~i & this.xyHashMask;
    // }

    return xHash + yHash * this.rowColumnCount;
    // + zHash * this.rowColumnCount * this.rowColumnCount;
};

Grid.prototype.addObject = function (obj, hash) {
    var objAABB,
        objHash,
        targetCell;

    // technically, passing this in this should save some computational effort when updating objects
    if (hash !== undefined) {
        objHash = hash;
    } else {
        objAABB = obj.getAABB();
        objHash = this.toHash(objAABB.min[0], objAABB.min[1]);
    }
    targetCell = this.allCells[objHash];

    if (targetCell.objectContainer.length === 0) {
        // insert this cell into occupied cells list
        targetCell.occupiedCellsIndex = this.occupiedCells.length;
        this.occupiedCells.push(targetCell);
    }

    // add meta data to obj, for fast update/removal
    obj.HSHG.objectContainerIndex = targetCell.objectContainer.length;
    obj.HSHG.hash = objHash;
    obj.HSHG.grid = this;
    obj.HSHG.allGridObjectsIndex = this.allObjects.length;
    // add obj to cell
    targetCell.objectContainer.push(obj);

    // we can assume that the targetCell is already a member of the occupied list

    // add to grid-global object list
    this.allObjects.push(obj);

    // do test for grid density
    if (this.allObjects.length / this.allCells.length > this._parentHierarchy.MAX_OBJECT_CELL_DENSITY) {
        // grid must be increased in size
        this.expandGrid();
    }
};

Grid.prototype.removeObject = function (obj) {
    var meta = obj.HSHG,
        hash,
        containerIndex,
        allGridObjectsIndex,
        cell,
        replacementCell,
        replacementObj;

    hash = meta.hash;
    containerIndex = meta.objectContainerIndex;
    allGridObjectsIndex = meta.allGridObjectsIndex;
    cell = this.allCells[hash];

    // remove object from cell object container
    if (cell.objectContainer.length === 1) {
        // this is the last object in the cell, so reset it
        cell.objectContainer.length = 0;

        // remove cell from occupied list
        if (cell.occupiedCellsIndex === this.occupiedCells.length - 1) {
            // special case if the cell is the newest in the list
            this.occupiedCells.pop();
        } else {
            replacementCell = this.occupiedCells.pop();
            replacementCell.occupiedCellsIndex = cell.occupiedCellsIndex;
            this.occupiedCells[cell.occupiedCellsIndex] = replacementCell;
        }

        cell.occupiedCellsIndex = null;
    } else {
        // there is more than one object in the container
        if (containerIndex === cell.objectContainer.length - 1) {
            // special case if the obj is the newest in the container
            cell.objectContainer.pop();
        } else {
            replacementObj = cell.objectContainer.pop();
            replacementObj.HSHG.objectContainerIndex = containerIndex;
            cell.objectContainer[containerIndex] = replacementObj;
        }
    }

    // remove object from grid object list
    if (allGridObjectsIndex === this.allObjects.length - 1) {
        this.allObjects.pop();
    } else {
        replacementObj = this.allObjects.pop();
        replacementObj.HSHG.allGridObjectsIndex = allGridObjectsIndex;
        this.allObjects[allGridObjectsIndex] = replacementObj;
    }
};

Grid.prototype.expandGrid = function () {
    var i, j,
        currentCellCount = this.allCells.length,
        currentRowColumnCount = this.rowColumnCount,
        currentXYHashMask = this.xyHashMask,

        newCellCount = currentCellCount * 4, // double each dimension
        newRowColumnCount = ~~Math.sqrt(newCellCount),
        newXYHashMask = newRowColumnCount - 1,
        allObjects = this.allObjects.slice(0), // duplicate array, not objects contained
        aCell,
        push = Array.prototype.push;

    // remove all objects
    for (i = 0; i < allObjects.length; i++) {
        this.removeObject(allObjects[i]);
    }

    // reset grid values, set new grid to be 4x larger than last
    this.rowColumnCount = newRowColumnCount;
    this.allCells = Array(this.rowColumnCount * this.rowColumnCount);
    this.xyHashMask = newXYHashMask;

    // initialize new cells
    this.initCells();

    // re-add all objects to grid
    for (i = 0; i < allObjects.length; i++) {
        this.addObject(allObjects[i]);
    }
};

/**
 * A cell of the grid
 *
 * @constructor
 * @return  void   desc
 */
function Cell() {
    this.objectContainer = [];
    this.neighborOffsetArray;
    this.occupiedCellsIndex = null;
    this.allCellsIndex = null;
}

// ---------------------------------------------------------------------
// EXPORTS
// ---------------------------------------------------------------------

HSHG._private = {
    Grid: Grid,
    Cell: Cell,
    testAABBOverlap: testAABBOverlap,
    getLongestAABBEdge: getLongestAABBEdge
};

class HSHGDetector {
    private hshg: any;

    constructor() {
        this.hshg = new HSHG();
    }

    addObject(o: any) {
        this.hshg.addObject(o);
    } 

    removeObject(o: any) {
        this.hshg.removeObject(o);
    }

    update() {
        this.hshg.update();
    }

    queryForCollisionPairs(): any[] {
        return this.hshg.queryForCollisionPairs();
    }
}

export { HSHGDetector }