ParametricGeometry constructor

ParametricGeometry(dynamic func, dynamic slices, dynamic stacks)

Implementation

ParametricGeometry(func, slices, stacks) : super() {
  parameters = {"func": func, "slices": slices, "stacks": stacks};

  // buffers

  List<num> indices = [];
  List<double> vertices = [];
  List<double> normals = [];
  List<double> uvs = [];

  var EPS = 0.00001;

  var normal = Vector3();

  var p0 = Vector3(), p1 = Vector3();
  var pu = Vector3(), pv = Vector3();

  // if ( func.length < 3 ) {

  // 	print( 'THREE.ParametricGeometry: Function must now modify a Vector3 as third parameter.' );

  // }

  // generate vertices, normals and uvs

  var sliceCount = slices + 1;

  for (var i = 0; i <= stacks; i++) {
    var v = i / stacks;

    for (var j = 0; j <= slices; j++) {
      var u = j / slices;

      // vertex

      func(u, v, p0);
      vertices.addAll([p0.x.toDouble(), p0.y.toDouble(), p0.z.toDouble()]);

      // normal

      // approximate tangent vectors via finite differences

      if (u - EPS >= 0) {
        func(u - EPS, v, p1);
        pu.subVectors(p0, p1);
      } else {
        func(u + EPS, v, p1);
        pu.subVectors(p1, p0);
      }

      if (v - EPS >= 0) {
        func(u, v - EPS, p1);
        pv.subVectors(p0, p1);
      } else {
        func(u, v + EPS, p1);
        pv.subVectors(p1, p0);
      }

      // cross product of tangent vectors returns surface normal

      normal.crossVectors(pu, pv).normalize();
      normals.addAll(
          [normal.x.toDouble(), normal.y.toDouble(), normal.z.toDouble()]);

      // uv

      uvs.addAll([u, v]);
    }
  }

  // generate indices

  for (var i = 0; i < stacks; i++) {
    for (var j = 0; j < slices; j++) {
      var a = i * sliceCount + j;
      var b = i * sliceCount + j + 1;
      var c = (i + 1) * sliceCount + j + 1;
      var d = (i + 1) * sliceCount + j;

      // faces one and two

      indices.addAll([a, b, d]);
      indices.addAll([b, c, d]);
    }
  }

  // build geometry

  setIndex(indices);
  setAttribute(
      'position', Float32BufferAttribute(Float32Array.from(vertices), 3));
  setAttribute(
      'normal', Float32BufferAttribute(Float32Array.from(normals), 3));
  setAttribute('uv', Float32BufferAttribute(Float32Array.from(uvs), 2));
}