幾何相交從直接幾何轉換為緩沖幾何

Question

我正在使用Three.js。 找到了一個由Benpurdy編寫的非常好的Decal庫。 它很容易修改，也使用了此處介紹的技術

但是，該技術使用幾何。 我正在進行的項目使用BufferGeometry。 我追蹤了幾何相交的代碼，無法弄清從面和頂點到屬性的轉換。

this.createGeometry = function(matrix, mesh) {

  var geom = mesh.geometry;

  var decalGeometry = new THREE.Geometry(); 

  var projectorInverse = matrix.clone().getInverse(matrix);
  var meshInverse = mesh.matrixWorld.clone().getInverse(mesh.matrixWorld);
  var faces = [];

  for(var i = 0; i < geom.faces.length; i++){

    var verts = [geom.faces[i].a, geom.faces[i].b, geom.faces[i].c];

    var pts = [];
    var valid = false;

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

      var vec = geom.vertices[verts[v]].clone();

      vec.applyMatrix4(mesh.matrixWorld);
      vec.applyMatrix4(matrix);

      if((vec.z > 1) || (vec.z < -1) || (vec.x > 1) || (vec.x < -1) || (vec.y > 1) || (vec.y < -1)) {
      } else {
        valid = true;
      }

      pts.push(vec);
    }

    if(valid) {

      var uv = [];
      for(var n = 0; n < 3; n++){
        uv.push(new THREE.Vector2( (pts[n].x + 1) / 2, (pts[n].y + 1) / 2));

        pts[n].applyMatrix4(projectorInverse);
        pts[n].applyMatrix4(meshInverse);

        decalGeometry.vertices.push( pts[n] );
      }

      // update UV's
      decalGeometry.faceVertexUvs[0].push(uv);

      var newFace = geom.faces[i].clone();

      newFace.a = decalGeometry.vertices.length - 3;
      newFace.b = decalGeometry.vertices.length - 2;
      newFace.c = decalGeometry.vertices.length - 1;

      decalGeometry.faces.push(newFace);
    }

  }

  return decalGeometry;
}

欣賞是否有人可以闡明如何實現這一目標？ 謝謝。

Answer 1

BufferGeometry()具有.fromGeometry()方法。 Populates this BufferGeometry with data from a Geometry object.

var geom = new THREE.BoxGeometry(1,1,1);
var bufGeom = new THREE.BufferGeometry().fromGeometry(geom);

UPD。 您可以使用另一種方式。

var bufGeom = new THREE.BoxBufferGeometry(1,1,1);
var geom = new THREE.Geometry().fromBufferGeometry(bufGeom);

Answer 2

最后，我編寫了另一個函數來計算帶有buffergeometry的交集，從而解決了該問題。 我花了一段時間嘗試了解原始的緩沖區幾何代碼。

this.createGeometryFromBufferGeometry = function(matrix, mesh) {

  var geom = mesh.geometry;

  var decalGeometry = new THREE.Geometry(); 

  var projectorInverse = matrix.clone().getInverse(matrix);
  var meshInverse = mesh.matrixWorld.clone().getInverse(mesh.matrixWorld);
  var faces = [];

  for(var i = 0; i < geom.attributes.position.array.length; i+=9){

    var pts = [];
    var valid = false;

    for(var v = 0; v < 9; v+=3) {


      var vec = new THREE.Vector3(geom.attributes.position.array[i+v],geom.attributes.position.array[i+v+1],geom.attributes.position.array[i+v+2]);
      console.log((i+v) + " " + (i+v+1) + " " + (i+v+2) );
      console.log(vec);

      vec.applyMatrix4(mesh.matrixWorld);
      vec.applyMatrix4(matrix);

      if((vec.z > 1) || (vec.z < -1) || (vec.x > 1) || (vec.x < -1) || (vec.y > 1) || (vec.y < -1)) {
      } else {
        valid = true;
      }

      pts.push(vec);
    }


    if(valid) {

      var uv = [];
      for(var n = 0; n < 3; n++){
        uv.push(new THREE.Vector2( (pts[n].x + 1) / 2, (pts[n].y + 1) / 2));

        pts[n].applyMatrix4(projectorInverse);
        pts[n].applyMatrix4(meshInverse);

        decalGeometry.vertices.push( pts[n] );
      }

      decalGeometry.faceVertexUvs[0].push(uv);

      var newFace = new THREE.Face3()

      newFace.a = decalGeometry.vertices.length - 3;
      newFace.b = decalGeometry.vertices.length - 2;
      newFace.c = decalGeometry.vertices.length - 1;

      decalGeometry.faces.push(newFace);
    }

  }
  return decalGeometry;
}

Answer 3

快速而骯臟的解決方案是從bufferGeometry創建幾何，並在計算后處置創建的幾何

this.compute = function()
{
   this.geometry = mesh.geometry
   if(this.geometry.attributes)
   {
        this.geometry = new THREE.Geometry().fromBufferGeometry(this.geometry);
        this.computeDecal();
        this.geometry.dispose();
    }
    else
    {
        this.computeDecal();
    }
}