RingGeometry constructor

RingGeometry([ dynamic innerRadius = 0.5, dynamic outerRadius = 1, dynamic thetaSegments = 8, dynamic phiSegments = 1, dynamic thetaStart = 0, dynamic thetaLength = Math.PI * 2, ])

Implementation

RingGeometry(
    [innerRadius = 0.5,
    outerRadius = 1,
    thetaSegments = 8,
    phiSegments = 1,
    thetaStart = 0,
    thetaLength = Math.PI * 2])
    : super() {
  parameters = {
    "innerRadius": innerRadius,
    "outerRadius": outerRadius,
    "thetaSegments": thetaSegments,
    "phiSegments": phiSegments,
    "thetaStart": thetaStart,
    "thetaLength": thetaLength
  };

  thetaSegments = Math.max<num>(3, thetaSegments);
  phiSegments = Math.max<num>(1, phiSegments);

  // buffers

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

  // some helper variables

  var radius = innerRadius;
  var radiusStep = ((outerRadius - innerRadius) / phiSegments);
  var vertex = Vector3();
  var uv = Vector2();

  // generate vertices, normals and uvs

  for (var j = 0; j <= phiSegments; j++) {
    for (var i = 0; i <= thetaSegments; i++) {
      // values are generate from the inside of the ring to the outside

      var segment = thetaStart + i / thetaSegments * thetaLength;

      // vertex

      vertex.x = radius * Math.cos(segment);
      vertex.y = radius * Math.sin(segment);

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

      // normal

      normals.addAll([0, 0, 1]);

      // uv

      uv.x = (vertex.x / outerRadius + 1) / 2;
      uv.y = (vertex.y / outerRadius + 1) / 2;

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

    // increase the radius for next row of vertices

    radius += radiusStep;
  }

  // indices

  for (var j = 0; j < phiSegments; j++) {
    var thetaSegmentLevel = j * (thetaSegments + 1);

    for (var i = 0; i < thetaSegments; i++) {
      var segment = i + thetaSegmentLevel;

      var a = segment;
      var b = segment + thetaSegments + 1;
      var c = segment + thetaSegments + 2;
      var d = segment + 1;

      // faces

      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));
}