WebCAD/src/Geometry/EdgeGeometry.ts

import { Box3, BufferGeometry, Face3, Float32BufferAttribute, Geometry, Line3, Triangle, Vector3 } from "three";
import { arraySortByNumber } from "../Common/ArrayExt";
import { FixIndex, ToFixed } from "../Common/Utils";
import { CSG } from "../csg/core/CSG";
import { FuzzyCSGFactory } from "../csg/core/FuzzyFactory3d";
import { Polygon } from "../csg/core/math/Polygon3";
import { Vector3D } from "../csg/core/math/Vector3";
import { equalv3 } from "./GeUtils";
//ref: https://github.com/mrdoob/js/issues/10517

const keys = ['a', 'b', 'c'];

export class EdgesGeometry extends BufferGeometry
{
    /**
     * 在使用Extrude实体的时候,有可能导致面无限分裂,并且有可能造成丢线问题,使用FromCSG方法可解.
     */
    FromGeometry(geometry, thresholdAngle: number = 1)
    {
        let geometry2: Geometry;

        if (geometry.isBufferGeometry)
            geometry2 = new Geometry().fromBufferGeometry(geometry);
        else
            geometry2 = geometry.clone();

        geometry2.mergeVertices();
        geometry2.computeFaceNormals();

        let vertices = geometry2.vertices;
        let faces = geometry2.faces;

        let count = faces.length;
        for (let i = 0; i < faces.length; i++)
        {
            if (faces.length > count * 2)
            {
                console.warn("EdgeGeometry的分裂已经到达2倍!");
                break;
            }
            let face = faces[i];

            if (FaceArea(face, vertices) < 1e-5)
                continue;

            for (let j = 0; j < 3; j++)
            {
                let e1 = face[keys[j]];
                let e2 = face[keys[(j + 1) % 3]];
                let e3 = face[keys[(j + 2) % 3]];

                let line = new Line3(vertices[e1], vertices[e2]);

                //split triangle
                for (let e = 0, l = vertices.length; e < l; e++)
                {
                    if (e === e1 || e === e2 || e === e3)
                        continue;

                    let p = vertices[e];
                    let closestPoint = line.closestPointToPoint(p, true, new Vector3());
                    if (equalv3(closestPoint, vertices[e1], 1e-5) || equalv3(closestPoint, vertices[e2]))
                        continue;
                    if (equalv3(closestPoint, p, 1e-5))
                    {
                        face["splitted"] = true;
                        let f1 = new Face3(e, e3, e1, face.normal);
                        let f2 = new Face3(e, e3, e2, face.normal);
                        faces.push(f1, f2);
                        break;
                    }
                }
                if (face["splitted"])
                    break;
            }
        }

        let edge = [0, 0];
        let hash: { [key: string]: { vert1: number, vert2: number, face1: Face3, face2?: Face3 } } = {};

        for (let i = 0, l = faces.length; i < l; i++)
        {
            let face = faces[i];

            if (face["splitted"]) continue;

            for (let j = 0; j < 3; j++)
            {
                edge[0] = face[keys[j]];
                edge[1] = face[keys[(j + 1) % 3]];
                arraySortByNumber(edge);

                let key = edge.toString();

                if (hash[key] === undefined)
                    hash[key] = { vert1: edge[0], vert2: edge[1], face1: face };
                else
                    hash[key].face2 = face;
            }
        }

        let coords: number[] = [];
        let thresholdDot = Math.cos(Math.PI / 180 * thresholdAngle);

        for (let key in hash)
        {
            let h = hash[key];

            // An edge is only rendered if the angle (in degrees) between the face normals of the adjoining faces exceeds this value. default = 1 degree.
            if (h.face2 && h.face1.normal.dot(h.face2.normal) <= thresholdDot)
            {
                let vertex = vertices[h.vert1];
                coords.push(vertex.x);
                coords.push(vertex.y);
                coords.push(vertex.z);

                vertex = vertices[h.vert2];
                coords.push(vertex.x);
                coords.push(vertex.y);
                coords.push(vertex.z);
            }
        }
        this.addAttribute('position', new Float32BufferAttribute(coords, 3));

        return this;
    }

    /**
     * 解决原来算法性能低下并且结果不理想的问题
     */
    FromCSG(csg: CSG)
    {
        let fuzzyfactory = new FuzzyCSGFactory();

        let polygonsPerPlane: { [key: number]: Polygon[] } = {};

        for (let polygon of csg.polygons)
        {
            let plane = polygon.plane;
            plane = fuzzyfactory.getPlane(plane);
            let tag = plane.getTag();
            if (!(tag in polygonsPerPlane)) polygonsPerPlane[tag] = [polygon];
            else polygonsPerPlane[tag].push(polygon);
        }

        let coords: number[] = [];

        for (let key in polygonsPerPlane)
        {
            this.PolygonsOutline(polygonsPerPlane[key], coords);
        }
        this.addAttribute('position', new Float32BufferAttribute(coords, 3));
        return this;
    }

    PolygonsOutline(polygons: Polygon[], coords: number[])
    {
        let pts: Vector3[] = [];
        let fp = new FuzzPoint();
        let record: { [key: string]: { p1: Vector3, p2: Vector3, count: number } } = {};

        for (let polygon of polygons)
        {
            for (let i = 0, count = polygon.vertices.length; i < count; i++)
            {
                let p = polygon.vertices[i];
                let np = fp.GetVector(p.pos);
                p.pos = np;
                if (!("_added_" in np))
                {
                    np["_added_"] = pts.length;
                    pts.push(np);
                }
            }
        }

        for (let polygon of polygons)
        {
            for (let i = 0, count = polygon.vertices.length; i < count; i++)
            {
                let p1 = polygon.vertices[i].pos as Vector3;
                let p2 = polygon.vertices[FixIndex(i + 1, count)].pos;

                let delta = p2.clone().sub(p1);
                let lengthSq = delta.dot(delta);

                let splitPts: { param: number, pt: Vector3 }[] = [];

                let box = new Box3().setFromPoints([p1, p2]).expandByVector(new Vector3(1, 1, 1));

                for (let p of pts)
                {
                    if (p === p1 || p === p2) continue;

                    if (!box.containsPoint(p)) continue;

                    let delta2 = p.clone().sub(p1);
                    let len2 = delta2.dot(delta);

                    let t = len2 / lengthSq;

                    if (t > 0 && t < 1)
                    {
                        let closestPoint = delta.clone().multiplyScalar(t).add(p1);
                        if (equalv3(closestPoint, p, 1e-3))
                            splitPts.push({ param: t, pt: p });
                    }
                }

                splitPts.sort((p1, p2) => p1.param - p2.param);
                splitPts.push({ param: 1, pt: p2 });

                let lastP = p1;

                for (let p of splitPts)
                {
                    let tag1 = lastP["_added_"] as number;
                    let tag2 = p.pt["_added_"] as number;

                    let key: string;
                    if (tag1 < tag2) key = `${tag1},${tag2}`;
                    else key = `${tag2},${tag1}`;

                    if (key in record)
                        record[key].count++;
                    else
                        record[key] = { p1: lastP, p2: p.pt, count: 1 };

                    lastP = p.pt;
                }
            }
        }

        for (let key in record)
        {
            let d = record[key];
            if (d.count === 1)
                coords.push(d.p1.x, d.p1.y, d.p1.z, d.p2.x, d.p2.y, d.p2.z);
        }
    }
}

class FuzzPoint
{
    private map: { [key: string]: Vector3D } = {};
    GetVector(v: Vector3D)
    {
        let key = `${ToFixed(v.x, 2)},${ToFixed(v.y, 2)},${ToFixed(v.z, 2)}`;
        if (key in this.map) return this.map[key];
        else this.map[key] = v;
        return v;
    }
}

let triangle = new Triangle();
function FaceArea(f: Face3, pts: Vector3[])
{
    triangle.a = pts[f.a];
    triangle.b = pts[f.b];
    triangle.c = pts[f.c];

    return triangle.getArea()
}