LatheGeometry constructor

LatheGeometry(dynamic points, { dynamic segments = 12, dynamic phiStart = 0, double phiLength = Math.PI * 2, })

Implementation

LatheGeometry(points,
    {segments = 12, phiStart = 0, double phiLength = Math.PI * 2})
    : super() {
  parameters = {
    "points": points,
    "segments": segments,
    "phiStart": phiStart,
    "phiLength": phiLength
  };

  segments = Math.floor(segments);

  // clamp phiLength so it's in range of [ 0, 2PI ]

  phiLength = MathUtils.clamp(phiLength, 0, Math.PI * 2);

  // buffers

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

  // helper variables

  var inverseSegments = 1.0 / segments;
  var vertex = Vector3();
  var uv = Vector2(null, null);
  var normal = Vector3();
  var curNormal = Vector3();
  var prevNormal = Vector3();
  double dx = 0;
  double dy = 0;

  // pre-compute normals for initial "meridian"

  for (var j = 0; j <= (points.length - 1); j++) {
    // special handling for 1st vertex on path
    if (j == 0) {
      dx = points[j + 1].x - points[j].x;
      dy = points[j + 1].y - points[j].y;

      normal.x = dy * 1.0;
      normal.y = -dx;
      normal.z = dy * 0.0;

      prevNormal.copy(normal);

      normal.normalize();

      initNormals.addAll([normal.x, normal.y, normal.z]);
    } else if (j == points.length - 1) {
      // special handling for last Vertex on path
      initNormals.addAll([prevNormal.x, prevNormal.y, prevNormal.z]);
    } else {
      // default handling for all vertices in between
      dx = points[j + 1].x - points[j].x;
      dy = points[j + 1].y - points[j].y;

      normal.x = dy * 1.0;
      normal.y = -dx;
      normal.z = dy * 0.0;

      curNormal.copy(normal);

      normal.x += prevNormal.x;
      normal.y += prevNormal.y;
      normal.z += prevNormal.z;

      normal.normalize();

      initNormals.addAll([normal.x, normal.y, normal.z]);

      prevNormal.copy(curNormal);
    }
  }

  // generate vertices, uvs and normals

  // generate vertices and uvs

  for (var i = 0; i <= segments; i++) {
    var phi = phiStart + i * inverseSegments * phiLength;

    var sin = Math.sin(phi);
    var cos = Math.cos(phi);

    for (var j = 0; j <= (points.length - 1); j++) {
      // vertex

      vertex.x = points[j].x * sin;
      vertex.y = points[j].y;
      vertex.z = points[j].x * cos;

      vertices.addAll(
          [vertex.x.toDouble(), vertex.y.toDouble(), vertex.z.toDouble()]);

      // uv

      uv.x = i / segments;
      uv.y = j / (points.length - 1);

      uvs.addAll([uv.x.toDouble(), uv.y.toDouble()]);

      // normal

      var x = initNormals[3 * j + 0] * sin;
      var y = initNormals[3 * j + 1];
      var z = initNormals[3 * j + 0] * cos;

      normals.addAll([x, y, z]);
    }
  }

  // indices

  for (var i = 0; i < segments; i++) {
    for (var j = 0; j < (points.length - 1); j++) {
      var base = j + i * points.length;

      var a = base;
      var b = base + points.length;
      var c = base + points.length + 1;
      var d = base + 1;

      // faces

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

  // build geometry

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