关于前端:基于webglthreejs的路面编辑

楔子

在很多利用中，特地是一些园区类的利用。都须要对园区的高空 环境进行展现，路面就是高空的一部分。
通常的做法是，都是建模的时候把相干的元素都建好，而后导入到展现零碎中进行展现。
不过有些状况下，可能建模并不太不便，所以三维编辑器能够间接进行简略的路面编辑显得挺有必要。

路面对象扩大

简略的路面心愿可能通过一个门路来生成。咱们晓得在 threejs 中有通过门路生成管路的对象，参考文章 WebGL 管网展现 (及 TubeGeometry 优化)，管路的横截面是一个圆形。路线的横截面冀望是一个矩形，因而，咱们能够仿照管路的思路制作一个相似的对象 PathRectGeometry，只是计算顶点的时候，横截面不再应用圆形，而是应用一个矩形，代码如下：

 let points = [new Vec3(-width/2,-height/2,0),new Vec3(-width/2,height/2,0),
        new Vec3(width/2,height/2,0),new Vec3(width/2,-height/2,0)] 
            if(!scope.clockwise) {points = [new Vec3(-width/2,-height/2,0),new Vec3(width/2,-height/2,0),
                    new Vec3(width/2,height/2,0),new Vec3(-width/2,height/2,0)];
            }
      for(let j = 0;j <= points.length;j ++) {
        let jj = j == points.length ? 0 : j; 
        let point = points[jj];
        let radius = Math.hypot(point.x,point.y);
        const sin = point.y / radius;
        const cos = point.x / radius;

          normal.x = (cos * N.x + sin * B.x);
                normal.y = (cos * N.y + sin * B.y);
                normal.z = (cos * N.z + sin * B.z);
                normal.normalize();

                normals.push(0,1,0);
            // vertex
                vertex.x = P.x + radius * normal.x;
                vertex.y = P.y + radius * normal.y;
                vertex.z = P.z + radius * normal.z;

                vertices.push(vertex.x, vertex.y, vertex.z);
      }

通过 PathRectGeometry 创建对象的成果如下图所示：

路面编辑

通过在立体下面打点来构建直线和贝塞尔曲线，而后通过构建得线条了生成门路，通过门路就能够生成路面成果，

 graph.getView().addEventListener("click", (event) => {let now = new Date().getTime();
        if (t != 0 && now - t < 500) {return;}
        t = now;
        if (path) {let pos = graph.getPositionOnPlaneByEvent(event, plane);
          constraintsHorizontalOrVertical(path, pos);
          path.lineTo(pos.x, pos.y, pos.z);
          tempPath = path.clone(tempPath);
          tempRoad.geometry.path = tempPath;
        }
      })

大略得过程如下所示：

在生成得门路上，会有很多控制点，拖动控制点能够二次批改门路：

生成连接处

两条路得连接处会有斑马线之类得，点击生成斑马线，能够通过算法主动计算斑马线，

// 找到 road1 到 road2 的 joint
    function createJointShape(road1, road2) {
      let path = road1.geometry.path;
      let path2 = road2.geometry.path;
      let lastPoint = path.points.at(-1);
      let lastCurve = path.curves.at(-1);
      let curves = path2.curves;
      console.log(curves);
      let minCurve, minDist = Infinity,
        minPoint
      for (let i = 0; i < curves.length; i++) {let curve = curves[i];
        if (curve.type == "LineCurve3") {
          let {
            dist,
            point
          } = findClosestPoint(lastPoint, curve.v1, curve.v2);
          if (dist < minDist) {
            minDist = dist;
            minPoint = point;
            minCurve = curve;
          }
        }
      }
      console.log(minCurve, minDist, minPoint);

      let v1 = lastCurve.v1,
        v2 = lastCurve.v2;
      let tagent = new dt.Vec3().subVectors(v2, v1);
      let up = new dt.Vec3(0, 1, 0);
      let cross = new dt.Vec3().cross(up, tagent);
      cross.normalize();
      let halfRoadWidth = 50;
      cross.multiplyScalar(halfRoadWidth);
      let cross2 = cross.clone().multiplyScalar(3.0);

      let p1 = lastPoint.clone().add(cross),
        p2 = lastPoint.clone().sub(cross);

      let sub = new dt.Vec3().subVectors(minPoint, lastPoint);
      console.log(sub.length(), minDist, halfRoadWidth)
      sub.setLength(minDist - halfRoadWidth);

      let joinPoint = new dt.Vec3().addVectors(lastPoint, sub);

      let halfSub = sub.clone().multiplyScalar(0.75);
      let p3Center = p1.clone().add(halfSub);
      let p4Center = p2.clone().add(halfSub);

      let p3 = joinPoint.clone().add(cross2);
      let p4 = joinPoint.clone().sub(cross2)

      let newPath = new dt.ShapePath();

      newPath.moveTo(p2.x, p2.z);
      newPath.quadraticCurveTo(p4Center.x, p4Center.z, p4.x, p4.z);
      newPath.lineTo(p3.x, p3.z);
      newPath.quadraticCurveTo(p3Center.x, p3Center.z, p1.x, p1.z);
      // newPath.closePath();
      // let geo = new dt.PathTubeGeometry(newPath, 64, 2);
      // let tube = new dt.Mesh(geo);

      let shapePath = newPath;

      const simpleShapes = shapePath.toShapes(true);

      var texture = graph.loadTexture("./road/001.jpg", {
        wrapT: dt.RepeatWrapping,
        wrapS: dt.RepeatWrapping,
      });
      texture.repeat.set(1 / 100, 1 / 100);
      texture.anisotropy = 16;

      let m1 = new dt.BasicMaterial({
        //  flatShading:true,
        map: texture,
        // envMap:envMap,
        // reflectivity:0.4,
        color: 0xffffff,
        toneMapped: false,
      });

      var geometry = new dt.ExtrudeGeometry(simpleShapes, {
        depth: 1,
        bevelEnabled: false,
        vertical: true,
      });
      var mesh = new dt.Mesh(geometry, m1);
      window.graph.getDataManager().add(mesh);

      road1.add(mesh);
    }

如下图所示：

结语

本文所示只是一个 demo 级别得尝试，如果要做一个强度得路面编辑器零碎，可能要思考得还有很多，比方多车道成果，更重得连接形态等等。这在后续得产品中会继续强化相干性能。

如果你有好的思路，也欢送和我交换。关注公号“ITMan 彪叔”能够增加作者微信进行交换，及时收到更多有价值的文章。