Cesium-Examples/examples/cesiumEx/ammolibs/ammo/ex/ConvexObjectBreaker.js

/**
 * @author yomboprime https://github.com/yomboprime
 *
 * @fileoverview This class can be used to subdivide a convex Geometry object into pieces.
 *
 * Usage:
 *
 * Use the function prepareBreakableObject to prepare a Mesh object to be broken.
 *
 * Then, call the various functions to subdivide the object (subdivideByImpact, cutByPlane)
 *
 * Sub-objects that are product of subdivision don't need prepareBreakableObject to be called on them.
 *
 * Requisites for the object:
 *
 *  - Mesh object must have a Geometry (not BufferGeometry) and a Material
 *
 *  - The Geometry must be convex (this is not tested in the library). You can create convex
 *  Geometries with THREE.ConvexGeometry. The BoxGeometry, SphereGeometry and other convex primitives
 *  can also be used.
 *
 * Note: This lib adds member variables to object's userData member and to its vertices.
 * (see prepareBreakableObject function)
 * Use with caution and read the code when using with other libs.
 *
 * @param {double} minSizeForBreak Min size a debris can have to break.
 * @param {double} smallDelta Max distance to consider that a point belongs to a plane.
 * 
  */

THREE.ConvexObjectBreaker = function (minSizeForBreak, smallDelta) {

    this.minSizeForBreak = minSizeForBreak || 1.4;
    this.smallDelta = smallDelta || 0.0001;

    this.tempLine1 = new THREE.Line3();
    this.tempPlane1 = new THREE.Plane();
    this.tempPlane2 = new THREE.Plane();
    this.tempCM1 = new THREE.Vector3();
    this.tempCM2 = new THREE.Vector3();
    this.tempVector3 = new THREE.Vector3();
    this.tempVector3_2 = new THREE.Vector3();
    this.tempVector3_3 = new THREE.Vector3();
    this.tempResultObjects = { object1: null, object2: null };

    this.segments = [];
    var n = 30 * 30;
    for (var i = 0; i < n; i++) {
        this.segments[i] = false;
    }

};

THREE.ConvexObjectBreaker.prototype = {

    constructor: THREE.ConvexObjectBreaker,

    prepareBreakableObject: function (object, mass, velocity, angularVelocity, breakable) {

        // object is a THREE.Object3d (normally a Mesh), must have a Geometry, and it must be convex.
        // Its material property is propagated to its children (sub-pieces)
        // mass must be > 0

        // Create vertices mark
        var geometry = object.geometry;
        var vertices = geometry.vertices;
        for (var i = 0, il = vertices.length; i < il; i++) {
            vertices[i].mark = 0;
        }

        var userData = object.userData;
        userData.mass = mass;
        userData.velocity = velocity.clone();
        userData.angularVelocity = angularVelocity.clone();
        userData.breakable = breakable;
    },

    /*
	 * @param {int} maxRadialIterations Iterations for radial cuts.
	 * @param {int} maxRandomIterations Max random iterations for not-radial cuts
	 * @param {double} minSizeForRadialSubdivision Min size a debris can have to break in radial subdivision.
	 *
	 * Returns the array of pieces
	 */
    subdivideByImpact: function (object, pointOfImpact, normal, maxRadialIterations, maxRandomIterations, minSizeForRadialSubdivision) {

        var debris = [];

        var tempPlane1 = this.tempPlane1;
        var tempPlane2 = this.tempPlane2;

        this.tempVector3.addVectors(pointOfImpact, normal);
        tempPlane1.setFromCoplanarPoints(pointOfImpact, object.position, this.tempVector3);

        var maxTotalIterations = maxRandomIterations + maxRadialIterations;

        var scope = this;

        function subdivideRadial(subObject, startAngle, endAngle, numIterations) {

            if (Math.random() < numIterations * 0.05 || numIterations > maxTotalIterations) {

                debris.push(subObject);

                return;

            }

            var angle = Math.PI;

            if (numIterations === 0) {

                tempPlane2.normal.copy(tempPlane1.normal);
                tempPlane2.constant = tempPlane1.constant;

            }
            else {

                if (numIterations <= maxRadialIterations) {

                    angle = (endAngle - startAngle) * (0.2 + 0.6 * Math.random()) + startAngle;

                    // Rotate tempPlane2 at impact point around normal axis and the angle
                    scope.tempVector3_2.copy(object.position).sub(pointOfImpact).applyAxisAngle(normal, angle).add(pointOfImpact);
                    tempPlane2.setFromCoplanarPoints(pointOfImpact, scope.tempVector3, scope.tempVector3_2);

                }
                else {

                    angle = ((0.5 * (numIterations & 1)) + 0.2 * (2 - Math.random())) * Math.PI;

                    // Rotate tempPlane2 at object position around normal axis and the angle
                    scope.tempVector3_2.copy(pointOfImpact).sub(subObject.position).applyAxisAngle(normal, angle).add(subObject.position);
                    scope.tempVector3_3.copy(normal).add(subObject.position);
                    tempPlane2.setFromCoplanarPoints(subObject.position, scope.tempVector3_3, scope.tempVector3_2);

                }

            }

            // Perform the cut
            scope.cutByPlane(subObject, tempPlane2, scope.tempResultObjects);

            var obj1 = scope.tempResultObjects.object1;
            var obj2 = scope.tempResultObjects.object2;

            if (obj1) {

                subdivideRadial(obj1, startAngle, angle, numIterations + 1);

            }

            if (obj2) {

                subdivideRadial(obj2, angle, endAngle, numIterations + 1);

            }

        }

        subdivideRadial(object, 0, 2 * Math.PI, 0);

        return debris;

    },

    cutByPlane: function (object, plane, output) {

        // Returns breakable objects in output.object1 and output.object2 members, the resulting 2 pieces of the cut.
        // object2 can be null if the plane doesn't cut the object.
        // object1 can be null only in case of internal error
        // Returned value is number of pieces, 0 for error.

        var geometry = object.geometry;
        var points = geometry.vertices;
        var faces = geometry.faces;

        var numPoints = points.length;

        var points1 = [];
        var points2 = [];

        var delta = this.smallDelta;

        // Reset vertices mark
        for (var i = 0; i < numPoints; i++) {
            points[i].mark = 0;
        }

        // Reset segments mark
        var numPointPairs = numPoints * numPoints;
        for (var i = 0; i < numPointPairs; i++) {
            this.segments[i] = false;
        }

        // Iterate through the faces to mark edges shared by coplanar faces
        for (var i = 0, il = faces.length - 1; i < il; i++) {

            var face1 = faces[i];

            for (var j = i + 1, jl = faces.length; j < jl; j++) {

                var face2 = faces[j];

                var coplanar = 1 - face1.normal.dot(face2.normal) < delta;

                if (coplanar) {

                    var a1 = face1.a;
                    var b1 = face1.b;
                    var c1 = face1.c;
                    var a2 = face2.a;
                    var b2 = face2.b;
                    var c2 = face2.c;


                    if (a1 === a2 || a1 === b2 || a1 === c2) {
                        if (b1 === a2 || b1 === b2 || b1 === c2) {
                            this.segments[a1 * numPoints + b1] = true;
                            this.segments[b1 * numPoints + a1] = true;
                        }
                        else {
                            this.segments[c1 * numPoints + a1] = true;
                            this.segments[a1 * numPoints + c1] = true;
                        }
                    }
                    else if (b1 === a2 || b1 === b2 || b1 === c2) {
                        this.segments[c1 * numPoints + b1] = true;
                        this.segments[b1 * numPoints + c1] = true;
                    }

                }

            }

        }

        // Transform the plane to object local space
        var localPlane = this.tempPlane1;

        THREE.ConvexObjectBreaker.transformPlaneToLocalSpace(plane, object.matrix, localPlane);

        // Iterate through the faces adding points to both pieces
        for (var i = 0, il = faces.length; i < il; i++) {

            var face = faces[i];

            for (var segment = 0; segment < 3; segment++) {

                var i0 = segment === 0 ? face.a : (segment === 1 ? face.b : face.c);
                var i1 = segment === 0 ? face.b : (segment === 1 ? face.c : face.a);

                var segmentState = this.segments[i0 * numPoints + i1];

                if (segmentState) {
                    // The segment already has been processed in another face
                    continue;
                }

                // Mark segment as processed (also inverted segment)
                this.segments[i0 * numPoints + i1] = true;
                this.segments[i1 * numPoints + i0] = true;

                var p0 = points[i0];
                var p1 = points[i1];

                if (p0.mark === 0) {

                    var d = localPlane.distanceToPoint(p0);

                    // mark: 1 for negative side, 2 for positive side, 3 for coplanar point
                    if (d > delta) {
                        p0.mark = 2;
                        points2.push(p0);
                    }
                    else if (d < -delta) {
                        p0.mark = 1;
                        points1.push(p0);
                    }
                    else {
                        p0.mark = 3;
                        points1.push(p0);
                        var p0_2 = p0.clone();
                        p0_2.mark = 3;
                        points2.push(p0_2);
                    }

                }

                if (p1.mark === 0) {

                    var d = localPlane.distanceToPoint(p1);

                    // mark: 1 for negative side, 2 for positive side, 3 for coplanar point
                    if (d > delta) {
                        p1.mark = 2;
                        points2.push(p1);
                    }
                    else if (d < -delta) {
                        p1.mark = 1;
                        points1.push(p1);
                    }
                    else {
                        p1.mark = 3;
                        points1.push(p1);
                        var p1_2 = p1.clone();
                        p1_2.mark = 3;
                        points2.push(p1_2);
                    }

                }

                var mark0 = p0.mark;
                var mark1 = p1.mark;

                if ((mark0 === 1 && mark1 === 2) || (mark0 === 2 && mark1 === 1)) {

                    // Intersection of segment with the plane

                    this.tempLine1.start.copy(p0);
                    this.tempLine1.end.copy(p1);
                    var intersection = localPlane.intersectLine(this.tempLine1);
                    if (intersection === undefined) {
                        // Shouldn't happen
                        console.error("Internal error: segment does not intersect plane.");
                        output.segmentedObject1 = null;
                        output.segmentedObject2 = null;
                        return 0;
                    }

                    intersection.mark = 1;
                    points1.push(intersection);
                    var intersection_2 = intersection.clone();
                    intersection_2.mark = 2;
                    points2.push(intersection_2);

                }

            }

        }

        // Calculate debris mass (very fast and imprecise):
        var newMass = object.userData.mass * 0.5;

        // Calculate debris Center of Mass (again fast and imprecise)
        this.tempCM1.set(0, 0, 0);
        var radius1 = 0;
        var numPoints1 = points1.length;
        if (numPoints1 > 0) {
            for (var i = 0; i < numPoints1; i++) {
                this.tempCM1.add(points1[i]);
            }
            this.tempCM1.divideScalar(numPoints1);
            for (var i = 0; i < numPoints1; i++) {
                var p = points1[i];
                p.sub(this.tempCM1);
                radius1 = Math.max(radius1, p.x, p.y, p.z);
            }
            this.tempCM1.add(object.position);
        }

        this.tempCM2.set(0, 0, 0);
        var radius2 = 0;
        var numPoints2 = points2.length;
        if (numPoints2 > 0) {
            for (var i = 0; i < numPoints2; i++) {
                this.tempCM2.add(points2[i]);
            }
            this.tempCM2.divideScalar(numPoints2);
            for (var i = 0; i < numPoints2; i++) {
                var p = points2[i];
                p.sub(this.tempCM2);
                radius2 = Math.max(radius2, p.x, p.y, p.z);
            }
            this.tempCM2.add(object.position);
        }

        var object1 = null;
        var object2 = null;

        var numObjects = 0;

        if (numPoints1 > 4) {

            object1 = new THREE.Mesh(new THREE.ConvexGeometry(points1), object.material);
            object1.position.copy(this.tempCM1);
            object1.quaternion.copy(object.quaternion);

            this.prepareBreakableObject(object1, newMass, object.userData.velocity, object.userData.angularVelocity, 2 * radius1 > this.minSizeForBreak);

            numObjects++;

        }

        if (numPoints2 > 4) {

            object2 = new THREE.Mesh(new THREE.ConvexGeometry(points2), object.material);
            object2.position.copy(this.tempCM2);
            object2.quaternion.copy(object.quaternion);

            this.prepareBreakableObject(object2, newMass, object.userData.velocity, object.userData.angularVelocity, 2 * radius2 > this.minSizeForBreak);

            numObjects++;

        }


        output.object1 = object1;
        output.object2 = object2;

        return numObjects;

    }

};

THREE.ConvexObjectBreaker.transformFreeVector = function (v, m) {

    // input:
    // vector interpreted as a free vector
    // THREE.Matrix4 orthogonal matrix (matrix without scale)

    var x = v.x, y = v.y, z = v.z;
    var e = m.elements;

    v.x = e[0] * x + e[4] * y + e[8] * z;
    v.y = e[1] * x + e[5] * y + e[9] * z;
    v.z = e[2] * x + e[6] * y + e[10] * z;

    return v;

};

THREE.ConvexObjectBreaker.transformFreeVectorInverse = function (v, m) {

    // input:
    // vector interpreted as a free vector
    // THREE.Matrix4 orthogonal matrix (matrix without scale)

    var x = v.x, y = v.y, z = v.z;
    var e = m.elements;

    v.x = e[0] * x + e[1] * y + e[2] * z;
    v.y = e[4] * x + e[5] * y + e[6] * z;
    v.z = e[8] * x + e[9] * y + e[10] * z;

    return v;

};

THREE.ConvexObjectBreaker.transformTiedVectorInverse = function (v, m) {

    // input:
    // vector interpreted as a tied (ordinary) vector
    // THREE.Matrix4 orthogonal matrix (matrix without scale)

    var x = v.x, y = v.y, z = v.z;
    var e = m.elements;

    v.x = e[0] * x + e[1] * y + e[2] * z - e[12];
    v.y = e[4] * x + e[5] * y + e[6] * z - e[13];
    v.z = e[8] * x + e[9] * y + e[10] * z - e[14];

    return v;

};

THREE.ConvexObjectBreaker.transformPlaneToLocalSpace = function () {

    var v1 = new THREE.Vector3();
    var m1 = new THREE.Matrix3();

    return function transformPlaneToLocalSpace(plane, m, resultPlane) {

        resultPlane.normal.copy(plane.normal);
        resultPlane.constant = plane.constant;

        var referencePoint = THREE.ConvexObjectBreaker.transformTiedVectorInverse(plane.coplanarPoint(v1), m);

        THREE.ConvexObjectBreaker.transformFreeVectorInverse(resultPlane.normal, m);

        // recalculate constant (like in setFromNormalAndCoplanarPoint)
        resultPlane.constant = -referencePoint.dot(resultPlane.normal);


    };

}();