Babylon.js/Babylon/Collisions/babylon.collider.js

var BABYLON = BABYLON || {};

(function () {
    BABYLON.Collider = function () {
        this.radius = new BABYLON.Vector3(1, 1, 1);
        this.retry = 0;

        this.basePointWorld = BABYLON.Vector3.Zero();
        this.velocityWorld = BABYLON.Vector3.Zero();
        this.normalizedVelocity = BABYLON.Vector3.Zero();
        
        // Internals
        this._trianglePlane = new BABYLON.Plane(0, 0, 0, 0);
        this._collisionPoint = BABYLON.Vector3.Zero();
        this._planeIntersectionPoint = BABYLON.Vector3.Zero();
        this._tempVector = BABYLON.Vector3.Zero();
        this._tempVector2 = BABYLON.Vector3.Zero();
        this._tempVector3 = BABYLON.Vector3.Zero();
        this._tempVector4 = BABYLON.Vector3.Zero();
        this._edge = BABYLON.Vector3.Zero();
        this._baseToVertex = BABYLON.Vector3.Zero();
        this._destinationPoint = BABYLON.Vector3.Zero();
        this._slidePlaneNormal = BABYLON.Vector3.Zero();
        this._displacementVector = BABYLON.Vector3.Zero();
    };

    // Methods
    BABYLON.Collider.prototype._initialize = function (source, dir, e) {
        this.velocity = dir;
        BABYLON.Vector3.NormalizeToRef(dir, this.normalizedVelocity);
        this.basePoint = source;

        source.multiplyToRef(this.radius, this.basePointWorld);
        dir.multiplyToRef(this.radius, this.velocityWorld);

        this.velocityWorldLength = this.velocityWorld.length();

        this.epsilon = e;
        this.collisionFound = false;
    };

    BABYLON.Collider.prototype._checkPointInTriangle = function (point, pa, pb, pc, n) {
        pa.subtractToRef(point, this._tempVector);
        pb.subtractToRef(point, this._tempVector2);

        BABYLON.Vector3.CrossToRef(this._tempVector, this._tempVector2, this._tempVector4);
        var d = BABYLON.Vector3.Dot(this._tempVector4, n);
        if (d < 0)
            return false;

        pc.subtractToRef(point, this._tempVector3);
        BABYLON.Vector3.CrossToRef(this._tempVector2, this._tempVector3, this._tempVector4);
        d = BABYLON.Vector3.Dot(this._tempVector4, n);
        if (d < 0)
            return false;

        BABYLON.Vector3.CrossToRef(this._tempVector3, this._tempVector, this._tempVector4);
        d = BABYLON.Vector3.Dot(this._tempVector4, n);
        return d >= 0;
    };

    var intersectBoxAASphere = function (boxMin, boxMax, sphereCenter, sphereRadius) {
        if (boxMin.x > sphereCenter.x + sphereRadius)
            return false;

        if (sphereCenter.x - sphereRadius > boxMax.x)
            return false;

        if (boxMin.y > sphereCenter.y + sphereRadius)
            return false;

        if (sphereCenter.y - sphereRadius > boxMax.y)
            return false;

        if (boxMin.z > sphereCenter.z + sphereRadius)
            return false;

        if (sphereCenter.z - sphereRadius > boxMax.z)
            return false;

        return true;
    };

    var getLowestRoot = function (a, b, c, maxR) {
        var determinant = b * b - 4.0 * a * c;
        var result = { root: 0, found: false };

        if (determinant < 0)
            return result;

        var sqrtD = Math.sqrt(determinant);
        var r1 = (-b - sqrtD) / (2.0 * a);
        var r2 = (-b + sqrtD) / (2.0 * a);

        if (r1 > r2) {
            var temp = r2;
            r2 = r1;
            r1 = temp;
        }

        if (r1 > 0 && r1 < maxR) {
            result.root = r1;
            result.found = true;
            return result;
        }

        if (r2 > 0 && r2 < maxR) {
            result.root = r2;
            result.found = true;
            return result;
        }

        return result;
    };

    BABYLON.Collider.prototype._canDoCollision = function (sphereCenter, sphereRadius, vecMin, vecMax) {
        var distance = BABYLON.Vector3.Distance(this.basePointWorld, sphereCenter);

        var max = Math.max(this.radius.x, this.radius.y);
        max = Math.max(max, this.radius.z);

        if (distance > this.velocityWorldLength + max + sphereRadius) {
            return false;
        }

        if (!intersectBoxAASphere(vecMin, vecMax, this.basePointWorld, this.velocityWorldLength + max))
            return false;

        return true;
    };

    BABYLON.Collider.prototype._testTriangle = function (subMesh, p1, p2, p3) {
        var t0;
        var embeddedInPlane = false;

        this._trianglePlane.copyFromPoints(p1, p2, p3);

        if ((!subMesh.getMaterial()) && !this._trianglePlane.isFrontFacingTo(this.normalizedVelocity, 0))
            return;

        var signedDistToTrianglePlane = this._trianglePlane.signedDistanceTo(this.basePoint);
        var normalDotVelocity = BABYLON.Vector3.Dot(this._trianglePlane.normal, this.velocity);

        if (normalDotVelocity == 0) {
            if (Math.abs(signedDistToTrianglePlane) >= 1.0)
                return;
            embeddedInPlane = true;
            t0 = 0;
        }
        else {
            t0 = (-1.0 - signedDistToTrianglePlane) / normalDotVelocity;
            var t1 = (1.0 - signedDistToTrianglePlane) / normalDotVelocity;

            if (t0 > t1) {
                var temp = t1;
                t1 = t0;
                t0 = temp;
            }

            if (t0 > 1.0 || t1 < 0.0)
                return;

            if (t0 < 0)
                t0 = 0;
            if (t0 > 1.0)
                t0 = 1.0;
        }

        this._collisionPoint.copyFromFloats(0, 0, 0);

        var found = false;
        var t = 1.0;

        if (!embeddedInPlane) {
            this.basePoint.subtractToRef(this._trianglePlane.normal, this._planeIntersectionPoint);
            this.velocity.scaleToRef(t0, this._tempVector);
            this._planeIntersectionPoint.addInPlace(this._tempVector);

            if (this._checkPointInTriangle(this._planeIntersectionPoint, p1, p2, p3, this._trianglePlane.normal)) {
                found = true;
                t = t0;
                this._collisionPoint.copyFrom(this._planeIntersectionPoint);
            }
        }

        if (!found) {
            var velocitySquaredLength = this.velocity.lengthSquared();

            var a = velocitySquaredLength;

            this.basePoint.subtractToRef(p1, this._tempVector);
            var b = 2.0 * (BABYLON.Vector3.Dot(this.velocity, this._tempVector));
            var c = this._tempVector.lengthSquared - 1.0;

            var lowestRoot = getLowestRoot(a, b, c, t);
            if (lowestRoot.found) {
                t = lowestRoot.root;
                found = true;
                this._collisionPoint.copyFrom(p1);
            }

            this.basePoint.subtractToRef(p2, this._tempVector);
            b = 2.0 * (BABYLON.Vector3.Dot(this.velocity, this._tempVector));
            c = this._tempVector.lengthSquared - 1.0;

            lowestRoot = getLowestRoot(a, b, c, t);
            if (lowestRoot.found) {
                t = lowestRoot.root;
                found = true;
                this._collisionPoint.copyFrom(p2);
            }

            this.basePoint.subtractToRef(p3, this._tempVector);
            b = 2.0 * (BABYLON.Vector3.Dot(this.velocity, this._tempVector));
            c = this._tempVector.lengthSquared - 1.0;

            lowestRoot = getLowestRoot(a, b, c, t);
            if (lowestRoot.found) {
                t = lowestRoot.root;
                found = true;
                this._collisionPoint.copyFrom(p3);
            }

            p2.subtractToRef(p1, this._edge);
            p1.subtractToRef(this.basePoint, this._baseToVertex);
            var edgeSquaredLength = this._edge.lengthSquared();
            var edgeDotVelocity = BABYLON.Vector3.Dot(this._edge, this.velocity);
            var edgeDotBaseToVertex = BABYLON.Vector3.Dot(this._edge, this._baseToVertex);

            a = edgeSquaredLength * (-velocitySquaredLength) + edgeDotVelocity * edgeDotVelocity;
            b = edgeSquaredLength * (2.0 * BABYLON.Vector3.Dot(this.velocity, this._baseToVertex)) - 2.0 * edgeDotVelocity * edgeDotBaseToVertex;
            c = edgeSquaredLength * (1.0 - this._baseToVertex.lengthSquared()) + edgeDotBaseToVertex * edgeDotBaseToVertex;

            lowestRoot = getLowestRoot(a, b, c, t);
            if (lowestRoot.found) {
                var f = (edgeDotVelocity * lowestRoot.root - edgeDotBaseToVertex) / edgeSquaredLength;

                if (f >= 0.0 && f <= 1.0) {
                    t = lowestRoot.root;
                    found = true;
                    this._edge.scaleInPlace(f);
                    p1.addToRef(this._edge, this._collisionPoint);
                }
            }

            p3.subtractToRef(p2, this._edge);
            p2.subtractToRef(this.basePoint, this._baseToVertex);
            edgeSquaredLength = this._edge.lengthSquared();
            edgeDotVelocity = BABYLON.Vector3.Dot(this._edge, this.velocity);
            edgeDotBaseToVertex = BABYLON.Vector3.Dot(this._edge, this._baseToVertex);

            a = edgeSquaredLength * (-velocitySquaredLength) + edgeDotVelocity * edgeDotVelocity;
            b = edgeSquaredLength * (2.0 * BABYLON.Vector3.Dot(this.velocity, this._baseToVertex)) - 2.0 * edgeDotVelocity * edgeDotBaseToVertex;
            c = edgeSquaredLength * (1.0 - this._baseToVertex.lengthSquared()) + edgeDotBaseToVertex * edgeDotBaseToVertex;
            lowestRoot = getLowestRoot(a, b, c, t);
            if (lowestRoot.found) {
                var f = (edgeDotVelocity * lowestRoot.root - edgeDotBaseToVertex) / edgeSquaredLength;

                if (f >= 0.0 && f <= 1.0) {
                    t = lowestRoot.root;
                    found = true;
                    this._edge.scaleInPlace(f);
                    p2.addToRef(this._edge, this._collisionPoint);
                }
            }

            p1.subtractToRef(p3, this._edge);
            p3.subtractToRef(this.basePoint, this._baseToVertex);
            edgeSquaredLength = this._edge.lengthSquared();
            edgeDotVelocity = BABYLON.Vector3.Dot(this._edge, this.velocity);
            edgeDotBaseToVertex = BABYLON.Vector3.Dot(this._edge, this._baseToVertex);

            a = edgeSquaredLength * (-velocitySquaredLength) + edgeDotVelocity * edgeDotVelocity;
            b = edgeSquaredLength * (2.0 * BABYLON.Vector3.Dot(this.velocity, this._baseToVertex)) - 2.0 * edgeDotVelocity * edgeDotBaseToVertex;
            c = edgeSquaredLength * (1.0 - this._baseToVertex.lengthSquared()) + edgeDotBaseToVertex * edgeDotBaseToVertex;

            lowestRoot = getLowestRoot(a, b, c, t);
            if (lowestRoot.found) {
                var f = (edgeDotVelocity * lowestRoot.root - edgeDotBaseToVertex) / edgeSquaredLength;

                if (f >= 0.0 && f <= 1.0) {
                    t = lowestRoot.root;
                    found = true;
                    this._edge.scaleInPlace(f);
                    p3.addToRef(this._edge, this._collisionPoint);
                }
            }
        }

        if (found) {
            var distToCollision = t * this.velocity.length();

            if (!this.collisionFound || distToCollision < this.nearestDistance) {
                if (!this.intersectionPoint) {
                    this.intersectionPoint = this._collisionPoint.clone();
                } else {
                    this.intersectionPoint.copyFrom(this._collisionPoint);
                }
                this.nearestDistance = distToCollision;                
                this.collisionFound = true;
            }
        }
    };

    BABYLON.Collider.prototype._collide = function (subMesh, pts, indices, indexStart, indexEnd, decal) {
        for (var i = indexStart; i < indexEnd; i += 3) {
            var p1 = pts[indices[i] - decal];
            var p2 = pts[indices[i + 1] - decal];
            var p3 = pts[indices[i + 2] - decal];

            this._testTriangle(subMesh, p3, p2, p1);
        }
    };
    
    BABYLON.Collider.prototype._getResponse = function(pos, vel) {
        pos.addToRef(vel, this._destinationPoint);
        vel.scaleInPlace((this.nearestDistance / vel.length()));

        this.basePoint.addToRef(vel, pos);
        pos.subtractToRef(this.intersectionPoint, this._slidePlaneNormal);
        this._slidePlaneNormal.normalize();
        this._slidePlaneNormal.scaleToRef(this.epsilon, this._displacementVector);

        pos.addInPlace(this._displacementVector);
        this.intersectionPoint.addInPlace(this._displacementVector);

        this._slidePlaneNormal.scaleInPlace(BABYLON.Plane.SignedDistanceToPlaneFromPositionAndNormal(this.intersectionPoint, this._slidePlaneNormal, this._destinationPoint));
        this._destinationPoint.subtractInPlace(this._slidePlaneNormal);

        this._destinationPoint.subtractToRef(this.intersectionPoint, vel);
    };

})();