visionforge/dataforge-vis-spatial-js/src/main/resources/ThreeCSG.js

import * as THREE from "three-full"

const EPSILON = 1e-5,
    COPLANAR = 0,
    FRONT = 1,
    BACK = 2,
    SPANNING = 3;

export function Geometry(geometry, transfer_matrix, nodeid, flippedMesh) {
    // Convert THREE.Geometry to ThreeBSP

    if (geometry instanceof THREE.Geometry) {
        this.matrix = null; // new THREE.Matrix4; not create matrix when do not needed
    } else if (geometry instanceof THREE.Mesh) {
        // #todo: add hierarchy support
        geometry.updateMatrix();
        transfer_matrix = this.matrix = geometry.matrix.clone();
        geometry = geometry.geometry;
    } else if (geometry instanceof Node) {
        this.tree = geometry;
        this.matrix = null; // new THREE.Matrix4;
        return this;
    } else if (geometry instanceof THREE.BufferGeometry) {
        var pos_buf = geometry.getAttribute('position').array,
            norm_buf = geometry.getAttribute('normal').array,
            polygons = [], polygon, vert1, vert2, vert3;

        for (var i = 0; i < pos_buf.length; i += 9) {
            polygon = new Polygon;

            vert1 = new Vertex(pos_buf[i], pos_buf[i + 1], pos_buf[i + 2], norm_buf[i], norm_buf[i + 1], norm_buf[i + 2]);
            if (transfer_matrix) vert1.applyMatrix4(transfer_matrix);

            vert2 = new Vertex(pos_buf[i + 3], pos_buf[i + 4], pos_buf[i + 5], norm_buf[i + 3], norm_buf[i + 4], norm_buf[i + 5]);
            if (transfer_matrix) vert2.applyMatrix4(transfer_matrix);

            vert3 = new Vertex(pos_buf[i + 6], pos_buf[i + 7], pos_buf[i + 8], norm_buf[i + 6], norm_buf[i + 7], norm_buf[i + 8]);
            if (transfer_matrix) vert3.applyMatrix4(transfer_matrix);

            if (flippedMesh) polygon.vertices.push(vert1, vert3, vert2);
            else polygon.vertices.push(vert1, vert2, vert3);

            polygon.calculateProperties();
            polygons.push(polygon);
        }

        this.tree = new Node(polygons, nodeid);
        if (nodeid !== undefined) this.maxid = this.tree.maxnodeid;
        return this;

    } else if (geometry.polygons && (geometry.polygons[0] instanceof Polygon)) {
        var polygons = geometry.polygons;

        for (var i = 0; i < polygons.length; ++i) {
            var polygon = polygons[i];
            if (transfer_matrix) {
                for (var n = 0; n < polygon.vertices.length; ++n)
                    polygon.vertices[n].applyMatrix4(transfer_matrix);
            }

            polygon.calculateProperties();
        }

        this.tree = new Node(polygons, nodeid);
        if (nodeid !== undefined) this.maxid = this.tree.maxnodeid;
        return this;

    } else {
        throw 'ThreeBSP: Given geometry is unsupported';
    }

    var polygons = [],
        nfaces = geometry.faces.length,
        face, polygon, vertex;

    for (var i = 0; i < nfaces; ++i) {
        face = geometry.faces[i];
        // faceVertexUvs = geometry.faceVertexUvs[0][i];
        polygon = new Polygon;

        if (face instanceof THREE.Face3) {
            vertex = geometry.vertices[face.a];
            // uvs = faceVertexUvs ? new THREE.Vector2( faceVertexUvs[0].x, faceVertexUvs[0].y ) : null;
            vertex = new Vertex(vertex.x, vertex.y, vertex.z, face.vertexNormals[0].x, face.vertexNormals[0].y, face.vertexNormals[0].z /*face.normal , uvs */);
            if (transfer_matrix) vertex.applyMatrix4(transfer_matrix);
            polygon.vertices.push(vertex);

            vertex = geometry.vertices[face.b];
            //uvs = faceVertexUvs ? new THREE.Vector2( faceVertexUvs[1].x, faceVertexUvs[1].y ) : null;
            vertex = new Vertex(vertex.x, vertex.y, vertex.z, face.vertexNormals[1].x, face.vertexNormals[1].y, face.vertexNormals[1].z/*face.normal , uvs */);
            if (transfer_matrix) vertex.applyMatrix4(transfer_matrix);
            polygon.vertices.push(vertex);

            vertex = geometry.vertices[face.c];
            // uvs = faceVertexUvs ? new THREE.Vector2( faceVertexUvs[2].x, faceVertexUvs[2].y ) : null;
            vertex = new Vertex(vertex.x, vertex.y, vertex.z, face.vertexNormals[2].x, face.vertexNormals[2].y, face.vertexNormals[2].z /*face.normal, uvs */);
            if (transfer_matrix) vertex.applyMatrix4(transfer_matrix);
            polygon.vertices.push(vertex);
        } else {
            throw 'Invalid face type at index ' + i;
        }

        polygon.calculateProperties();
        polygons.push(polygon);
    }

    this.tree = new Node(polygons, nodeid);
    if (nodeid !== undefined) this.maxid = this.tree.maxnodeid;
}

Geometry.prototype.subtract = function (other_tree) {
    var a = this.tree.clone(),
        b = other_tree.tree.clone();

    a.invert();
    a.clipTo(b);
    b.clipTo(a);
    b.invert();
    b.clipTo(a);
    b.invert();
    a.build(b.allPolygons());
    a.invert();
    a = new Geometry(a);
    a.matrix = this.matrix;
    return a;
};

Geometry.prototype.union = function (other_tree) {
    var a = this.tree.clone(),
        b = other_tree.tree.clone();

    a.clipTo(b);
    b.clipTo(a);
    b.invert();
    b.clipTo(a);
    b.invert();
    a.build(b.allPolygons());
    a = new Geometry(a);
    a.matrix = this.matrix;
    return a;
};

Geometry.prototype.intersect = function (other_tree) {
    var a = this.tree.clone(),
        b = other_tree.tree.clone();

    a.invert();
    b.clipTo(a);
    b.invert();
    a.clipTo(b);
    b.clipTo(a);
    a.build(b.allPolygons());
    a.invert();
    a = new Geometry(a);
    a.matrix = this.matrix;
    return a;
};

Geometry.prototype.tryToCompress = function (polygons) {

    if (this.maxid === undefined) return;

    var arr = [], parts, foundpair,
        nreduce = 0, n, len = polygons.length,
        p, p1, p2, i1, i2;

    // sort out polygons
    for (n = 0; n < len; ++n) {
        p = polygons[n];
        if (p.id === undefined) continue;
        if (arr[p.id] === undefined) arr[p.id] = [];

        arr[p.id].push(p);
    }

    for (n = 0; n < arr.length; ++n) {
        parts = arr[n];
        if (parts === undefined) continue;

        len = parts.length;

        foundpair = (len > 1);

        while (foundpair) {
            foundpair = false;

            for (i1 = 0; i1 < len - 1; ++i1) {
                p1 = parts[i1];
                if (!p1 || !p1.parent) continue;
                for (i2 = i1 + 1; i2 < len; ++i2) {
                    p2 = parts[i2];
                    if (p2 && (p1.parent === p2.parent) && (p1.nsign === p2.nsign)) {

                        if (p1.nsign !== p1.parent.nsign) p1.parent.flip();

                        nreduce++;
                        parts[i1] = p1.parent;
                        parts[i2] = null;
                        if (p1.parent.vertices.length < 3) console.log('something wrong with parent');
                        foundpair = true;
                        break;
                    }
                }
            }
        }
    }

    if (nreduce > 0) {
        polygons.splice(0, polygons.length);

        for (n = 0; n < arr.length; ++n) {
            parts = arr[n];
            if (parts !== undefined)
                for (i1 = 0, len = parts.length; i1 < len; ++i1)
                    if (parts[i1]) polygons.push(parts[i1]);
        }

    }
};

Geometry.prototype.direct_subtract = function (other_tree) {
    var a = this.tree,
        b = other_tree.tree;
    a.invert();
    a.clipTo(b);
    b.clipTo(a);
    b.invert();
    b.clipTo(a);
    b.invert();
    a.build(b.collectPolygons([]));
    a.invert();
    return this;
};

Geometry.prototype.direct_union = function (other_tree) {
    var a = this.tree,
        b = other_tree.tree;

    a.clipTo(b);
    b.clipTo(a);
    b.invert();
    b.clipTo(a);
    b.invert();
    a.build(b.collectPolygons([]));
    return this;
};

Geometry.prototype.direct_intersect = function (other_tree) {
    var a = this.tree,
        b = other_tree.tree;

    a.invert();
    b.clipTo(a);
    b.invert();
    a.clipTo(b);
    b.clipTo(a);
    a.build(b.collectPolygons([]));
    a.invert();
    return this;
};

export function CreateNormal(axis_name, pos, size) {
    // create geometry to make cut on specified axis

    var vert1, vert2, vert3;

    if (!size || (size < 10000)) size = 10000;

    switch (axis_name) {
        case "x":
            vert1 = new Vertex(pos, -3 * size, size, 1, 0, 0),
                vert3 = new Vertex(pos, size, size, 1, 0, 0),
                vert2 = new Vertex(pos, size, -3 * size, 1, 0, 0);
            break;
        case "y":
            vert1 = new Vertex(-3 * size, pos, size, 0, 1, 0),
                vert2 = new Vertex(size, pos, size, 0, 1, 0),
                vert3 = new Vertex(size, pos, -3 * size, 0, 1, 0);
            break;
        case "z":
            vert1 = new Vertex(-3 * size, size, pos, 0, 0, 1),
                vert3 = new Vertex(size, size, pos, 0, 0, 1),
                vert2 = new Vertex(size, -3 * size, pos, 0, 0, 1);
            break;
    }

    var polygon = new Polygon([vert1, vert2, vert3]);
    polygon.calculateProperties();

    var node = new Node([polygon]);

    return new Geometry(node);
}

Geometry.prototype.cut_from_plane = function (other_tree) {
    // just cut peaces from second geometry, which just simple plane

    var a = this.tree,
        b = other_tree.tree;

    a.invert();
    b.clipTo(a);

    return this;
};


Geometry.prototype.toGeometry = function () {
    var i, j,
        matrix = this.matrix ? new THREE.Matrix4().getInverse(this.matrix) : null,
        geometry = new THREE.Geometry(),
        polygons = this.tree.collectPolygons([]),
        polygon_count = polygons.length,
        polygon, polygon_vertice_count,
        vertice_dict = {},
        vertex_idx_a, vertex_idx_b, vertex_idx_c,
        vertex, face;

    for (i = 0; i < polygon_count; ++i) {
        polygon = polygons[i];
        polygon_vertice_count = polygon.vertices.length;

        for (j = 2; j < polygon_vertice_count; ++j) {
            // verticeUvs = [];

            vertex = polygon.vertices[0];
            // verticeUvs.push( new THREE.Vector2( vertex.uv.x, vertex.uv.y ) );
            vertex = new THREE.Vector3(vertex.x, vertex.y, vertex.z);
            if (matrix) vertex.applyMatrix4(matrix);

            if (typeof vertice_dict[vertex.x + ',' + vertex.y + ',' + vertex.z] !== 'undefined') {
                vertex_idx_a = vertice_dict[vertex.x + ',' + vertex.y + ',' + vertex.z];
            } else {
                geometry.vertices.push(vertex);
                vertex_idx_a = vertice_dict[vertex.x + ',' + vertex.y + ',' + vertex.z] = geometry.vertices.length - 1;
            }

            vertex = polygon.vertices[j - 1];
            // verticeUvs.push( new THREE.Vector2( vertex.uv.x, vertex.uv.y ) );
            vertex = new THREE.Vector3(vertex.x, vertex.y, vertex.z);
            if (matrix) vertex.applyMatrix4(matrix);
            if (typeof vertice_dict[vertex.x + ',' + vertex.y + ',' + vertex.z] !== 'undefined') {
                vertex_idx_b = vertice_dict[vertex.x + ',' + vertex.y + ',' + vertex.z];
            } else {
                geometry.vertices.push(vertex);
                vertex_idx_b = vertice_dict[vertex.x + ',' + vertex.y + ',' + vertex.z] = geometry.vertices.length - 1;
            }

            vertex = polygon.vertices[j];
            // verticeUvs.push( new THREE.Vector2( vertex.uv.x, vertex.uv.y ) );
            vertex = new THREE.Vector3(vertex.x, vertex.y, vertex.z);
            if (matrix) vertex.applyMatrix4(matrix);
            if (typeof vertice_dict[vertex.x + ',' + vertex.y + ',' + vertex.z] !== 'undefined') {
                vertex_idx_c = vertice_dict[vertex.x + ',' + vertex.y + ',' + vertex.z];
            } else {
                geometry.vertices.push(vertex);
                vertex_idx_c = vertice_dict[vertex.x + ',' + vertex.y + ',' + vertex.z] = geometry.vertices.length - 1;
            }

            face = new THREE.Face3(
                vertex_idx_a,
                vertex_idx_b,
                vertex_idx_c,
                new THREE.Vector3(polygon.normal.x, polygon.normal.y, polygon.normal.z)
            );

            geometry.faces.push(face);
            // geometry.faceVertexUvs[0].push( verticeUvs );
        }

    }
    return geometry;
};

Geometry.prototype.scale = function (x, y, z) {
    // try to scale as THREE.BufferGeometry
    var polygons = this.tree.collectPolygons([]);

    for (var i = 0; i < polygons.length; ++i) {
        var polygon = polygons[i];
        for (var k = 0; k < polygon.vertices.length; ++k) {
            var v = polygon.vertices[k];
            v.x *= x;
            v.y *= y;
            v.z *= z;
        }
        delete polygon.normal;
        polygon.calculateProperties();
    }
};

Geometry.prototype.toPolygons = function () {
    var polygons = this.tree.collectPolygons([]);

    this.tryToCompress(polygons);

    for (var i = 0; i < polygons.length; ++i) {
        delete polygons[i].id;
        delete polygons[i].parent;
    }

    return polygons;
};

Geometry.prototype.toBufferGeometry = function () {
    return CreateBufferGeometry(this.toPolygons());
};

export function CreateBufferGeometry(polygons) {
    var i, j, polygon_count = polygons.length, buf_size = 0;

    for (i = 0; i < polygon_count; ++i)
        buf_size += (polygons[i].vertices.length - 2) * 9;

    var positions_buf = new Float32Array(buf_size),
        normals_buf = new Float32Array(buf_size),
        iii = 0, polygon;

    function CopyVertex(vertex) {

        positions_buf[iii] = vertex.x;
        positions_buf[iii + 1] = vertex.y;
        positions_buf[iii + 2] = vertex.z;

        normals_buf[iii] = polygon.nsign * vertex.nx;
        normals_buf[iii + 1] = polygon.nsign * vertex.ny;
        normals_buf[iii + 2] = polygon.nsign * vertex.nz;
        iii += 3;
    }

    for (i = 0; i < polygon_count; ++i) {
        polygon = polygons[i];
        for (j = 2; j < polygon.vertices.length; ++j) {
            CopyVertex(polygon.vertices[0]);
            CopyVertex(polygon.vertices[j - 1]);
            CopyVertex(polygon.vertices[j]);
        }
    }

    var geometry = new THREE.BufferGeometry();
    geometry.addAttribute('position', new THREE.BufferAttribute(positions_buf, 3));
    geometry.addAttribute('normal', new THREE.BufferAttribute(normals_buf, 3));

    // geometry.computeVertexNormals();
    return geometry;
}

Geometry.prototype.toMesh = function (material) {
    var geometry = this.toGeometry(),
        mesh = new THREE.Mesh(geometry, material);

    if (this.matrix) {
        mesh.position.setFromMatrixPosition(this.matrix);
        mesh.rotation.setFromRotationMatrix(this.matrix);
    }

    return mesh;
};

export class Polygon {
    constructor(vertices, normal, w) {
        if (!(vertices instanceof Array)) {
            vertices = [];
        }

        this.vertices = vertices;
        this.nsign = 1;
        if (vertices.length > 0) {
            this.calculateProperties();
        } else {
            this.normal = this.w = undefined;
        }
    };
}


Polygon.prototype.copyProperties = function (parent, more) {
    this.normal = parent.normal; // .clone();
    this.w = parent.w;
    this.nsign = parent.nsign;
    if (more && (parent.id !== undefined)) {
        this.id = parent.id;
        this.parent = parent;
    }
    return this;
};

Polygon.prototype.calculateProperties = function () {
    if (this.normal) return;

    var a = this.vertices[0],
        b = this.vertices[1],
        c = this.vertices[2];

    this.nsign = 1;

    this.normal = b.clone().subtract(a).cross(
        c.clone().subtract(a)
    ).normalize();

    this.w = this.normal.clone().dot(a);
    return this;
};

Polygon.prototype.clone = function () {
    var vertice_count = this.vertices.length,
        polygon = new Polygon;

    for (var i = 0; i < vertice_count; ++i)
        polygon.vertices.push(this.vertices[i].clone());

    return polygon.copyProperties(this);
};

Polygon.prototype.flip = function () {

    /// normal is not changed, only sign variable
    //this.normal.multiplyScalar( -1 );
    //this.w *= -1;

    this.nsign *= -1;

    this.vertices.reverse();

    return this;
};

Polygon.prototype.classifyVertex = function (vertex) {
    var side_value = this.nsign * (this.normal.dot(vertex) - this.w);

    if (side_value < -EPSILON) return BACK;
    if (side_value > EPSILON) return FRONT;
    return COPLANAR;
};

Polygon.prototype.classifySide = function (polygon) {
    var i, classification,
        num_positive = 0, num_negative = 0,
        vertice_count = polygon.vertices.length;

    for (i = 0; i < vertice_count; ++i) {
        classification = this.classifyVertex(polygon.vertices[i]);
        if (classification === FRONT) {
            ++num_positive;
        } else if (classification === BACK) {
            ++num_negative;
        }
    }

    if (num_positive > 0 && num_negative === 0) return FRONT;
    if (num_positive === 0 && num_negative > 0) return BACK;
    if (num_positive === 0 && num_negative === 0) return COPLANAR;
    return SPANNING;
};

Polygon.prototype.splitPolygon = function (polygon, coplanar_front, coplanar_back, front, back) {
    var classification = this.classifySide(polygon);

    if (classification === COPLANAR) {

        ((this.nsign * polygon.nsign * this.normal.dot(polygon.normal) > 0) ? coplanar_front : coplanar_back).push(polygon);

    } else if (classification === FRONT) {

        front.push(polygon);

    } else if (classification === BACK) {

        back.push(polygon);

    } else {

        var vertice_count = polygon.vertices.length,
            nnx = this.normal.x,
            nny = this.normal.y,
            nnz = this.normal.z,
            i, j, ti, tj, vi, vj,
            t, v,
            f = [], b = [];

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

            j = (i + 1) % vertice_count;
            vi = polygon.vertices[i];
            vj = polygon.vertices[j];
            ti = this.classifyVertex(vi);
            tj = this.classifyVertex(vj);

            if (ti != BACK) f.push(vi);
            if (ti != FRONT) b.push(vi);
            if ((ti | tj) === SPANNING) {
                // t = ( this.w - this.normal.dot( vi ) ) / this.normal.dot( vj.clone().subtract( vi ) );
                //v = vi.clone().lerp( vj, t );

                t = (this.w - (nnx * vi.x + nny * vi.y + nnz * vi.z)) / (nnx * (vj.x - vi.x) + nny * (vj.y - vi.y) + nnz * (vj.z - vi.z));

                v = vi.interpolate(vj, t);
                f.push(v);
                b.push(v);
            }
        }

        //if ( f.length >= 3 ) front.push( new Polygon( f ).calculateProperties() );
        //if ( b.length >= 3 ) back.push( new Polygon( b ).calculateProperties() );
        if (f.length >= 3) front.push(new Polygon(f).copyProperties(polygon, true));
        if (b.length >= 3) back.push(new Polygon(b).copyProperties(polygon, true));
    }
};

export class Vertex {
    constructor(x, y, z, nx, ny, nz) {
        this.x = x;
        this.y = y;
        this.z = z;
        this.nx = nx;
        this.ny = ny;
        this.nz = nz;
    };
}

Vertex.prototype.setnormal = function (nx, ny, nz) {
    this.nx = nx;
    this.ny = ny;
    this.nz = nz;
};

Vertex.prototype.clone = function () {
    return new Vertex(this.x, this.y, this.z, this.nx, this.ny, this.nz);
};

Vertex.prototype.add = function (vertex) {
    this.x += vertex.x;
    this.y += vertex.y;
    this.z += vertex.z;
    return this;
};

Vertex.prototype.subtract = function (vertex) {
    this.x -= vertex.x;
    this.y -= vertex.y;
    this.z -= vertex.z;
    return this;
};

Vertex.prototype.multiplyScalar = function (scalar) {
    this.x *= scalar;
    this.y *= scalar;
    this.z *= scalar;
    return this;
};

Vertex.prototype.cross = function (vertex) {
    var x = this.x,
        y = this.y,
        z = this.z;

    this.x = y * vertex.z - z * vertex.y;
    this.y = z * vertex.x - x * vertex.z;
    this.z = x * vertex.y - y * vertex.x;

    return this;
};

Vertex.prototype.normalize = function () {
    var length = Math.sqrt(this.x * this.x + this.y * this.y + this.z * this.z);

    this.x /= length;
    this.y /= length;
    this.z /= length;

    return this;
};

Vertex.prototype.dot = function (vertex) {
    return this.x * vertex.x + this.y * vertex.y + this.z * vertex.z;
};

Vertex.prototype.diff = function (vertex) {
    var dx = (this.x - vertex.x),
        dy = (this.y - vertex.y),
        dz = (this.z - vertex.z),
        len2 = this.x * this.x + this.y * this.y + this.z * this.z;

    return (dx * dx + dy * dy + dz * dz) / (len2 > 0 ? len2 : 1e-10);
};

/*
   Vertex.prototype.lerp = function( a, t ) {
      this.add(
         a.clone().subtract( this ).multiplyScalar( t )
      );

      this.normal.add(
         a.normal.clone().sub( this.normal ).multiplyScalar( t )
      );

      //this.uv.add(
      //   a.uv.clone().sub( this.uv ).multiplyScalar( t )
      //);

      return this;
   };
   Vertex.prototype.interpolate = function( other, t ) {
      return this.clone().lerp( other, t );
   };
*/

Vertex.prototype.interpolate = function (a, t) {
    var t1 = 1 - t;
    return new Vertex(this.x * t1 + a.x * t, this.y * t1 + a.y * t, this.z * t1 + a.z * t,
        this.nx * t1 + a.nx * t, this.ny * t1 + a.ny * t, this.nz * t1 + a.nz * t);
};

Vertex.prototype.applyMatrix4 = function (m) {

    // input: THREE.Matrix4 affine matrix

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

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

    x = this.nx;
    y = this.ny;
    z = this.nz;

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

    return this;
};

// ================================================================================================

export class Node {
    constructor(polygons, nodeid) {
        this.polygons = [];
        this.front = this.back = undefined;

        if (!(polygons instanceof Array) || polygons.length === 0) return;

        this.divider = polygons[0].clone();

        var polygon_count = polygons.length,
            front = [], back = [];

        for (var i = 0; i < polygon_count; ++i) {
            if (nodeid !== undefined) {
                polygons[i].id = nodeid++;
                delete polygons[i].parent;
            }

            this.divider.splitPolygon(polygons[i], this.polygons, this.polygons, front, back);
        }

        if (nodeid !== undefined) this.maxnodeid = nodeid;

        if (front.length > 0)
            this.front = new Node(front);

        if (back.length > 0)
            this.back = new Node(back);
    };
}

Node.isConvex = function (polygons) {
    var i, j, len = polygons.length;
    for (i = 0; i < len; ++i)
        for (j = 0; j < len; ++j)
            if (i !== j && polygons[i].classifySide(polygons[j]) !== BACK) return false;
    return true;
};

Node.prototype.build = function (polygons) {
    var polygon_count = polygons.length,
        front = [], back = [];

    if (!this.divider)
        this.divider = polygons[0].clone();

    for (var i = 0; i < polygon_count; ++i)
        this.divider.splitPolygon(polygons[i], this.polygons, this.polygons, front, back);

    if (front.length > 0) {
        if (!this.front) this.front = new Node();
        this.front.build(front);
    }

    if (back.length > 0) {
        if (!this.back) this.back = new Node();
        this.back.build(back);
    }
};

Node.prototype.collectPolygons = function (arr) {
    var len = this.polygons.length;
    for (var i = 0; i < len; ++i) arr.push(this.polygons[i]);
    if (this.front) this.front.collectPolygons(arr);
    if (this.back) this.back.collectPolygons(arr);
    return arr;
};

Node.prototype.allPolygons = function () {
    var polygons = this.polygons.slice();
    if (this.front) polygons = polygons.concat(this.front.allPolygons());
    if (this.back) polygons = polygons.concat(this.back.allPolygons());
    return polygons;
};

Node.prototype.numPolygons = function () {
    var res = this.polygons.length;
    if (this.front) res += this.front.numPolygons();
    if (this.back) res += this.back.numPolygons();
    return res;
};

Node.prototype.clone = function () {
    var node = new Node();

    node.divider = this.divider.clone();
    node.polygons = this.polygons.map(function (polygon) {
        return polygon.clone();
    });
    node.front = this.front && this.front.clone();
    node.back = this.back && this.back.clone();

    return node;
};

Node.prototype.invert = function () {
    var polygon_count = this.polygons.length;

    for (var i = 0; i < polygon_count; ++i)
        this.polygons[i].flip();

    this.divider.flip();
    if (this.front) this.front.invert();
    if (this.back) this.back.invert();

    var temp = this.front;
    this.front = this.back;
    this.back = temp;

    return this;
};

Node.prototype.clipPolygons = function (polygons) {

    if (!this.divider) return polygons.slice();

    var polygon_count = polygons.length, front = [], back = [];

    for (var i = 0; i < polygon_count; ++i)
        this.divider.splitPolygon(polygons[i], front, back, front, back);

    if (this.front) front = this.front.clipPolygons(front);
    if (this.back) back = this.back.clipPolygons(back);
    else back = [];

    return front.concat(back);
};

Node.prototype.clipTo = function (node) {
    this.polygons = node.clipPolygons(this.polygons);
    if (this.front) this.front.clipTo(node);
    if (this.back) this.back.clipTo(node);
};