ConeGeometry constructor

ConeGeometry(double bottomRadius, double topRadius, double height, int radialSubdivisions, int verticalSubdivisions, [ bool topCap = true, bool bottomCap = true, ])

Implementation

ConeGeometry(
  this.bottomRadius,
  this.topRadius,
  this.height,
  this.radialSubdivisions,
  this.verticalSubdivisions, [
  this.topCap = true,
  this.bottomCap = true,
]) {
  if (radialSubdivisions < 3) {
    throw ('radialSubdivisions must be 3 or greater');
  }

  if (verticalSubdivisions < 1) {
    throw ('verticalSubdivisions must be 1 or greater');
  }

  int extra = (topCap ? 2 : 0) + (bottomCap ? 2 : 0);
  int vertsAroundEdge = radialSubdivisions + 1;

  // The slant of the cone is constant across its surface
  double slant = math.atan2(bottomRadius - topRadius, height);
  double cosSlant = math.cos(slant);
  double sinSlant = math.sin(slant);

  int start = topCap ? -2 : 0;
  int end = verticalSubdivisions + (bottomCap ? 2 : 0);

  for (int yy = start; yy <= end; ++yy) {
    double v = yy / verticalSubdivisions;
    double y = height * v;
    double ringRadius;

    if (yy < 0) {
      y = 0;
      v = 1;
      ringRadius = bottomRadius;
    } else if (yy > verticalSubdivisions) {
      y = height;
      v = 1;
      ringRadius = topRadius;
    } else {
      ringRadius = bottomRadius + (topRadius - bottomRadius) * (yy / verticalSubdivisions);
    }

    if (yy == -2 || yy == verticalSubdivisions + 2) {
      ringRadius = 0;
      v = 0;
    }

    y -= height / 2;
    for (var ii = 0; ii < vertsAroundEdge; ++ii) {
      var sin = math.sin(ii * math.pi * 2 / radialSubdivisions);
      var cos = math.cos(ii * math.pi * 2 / radialSubdivisions);

      vertices.addAll([
        sin * ringRadius,
        y,
        cos * ringRadius,
      ]);

      normals.addAll([
        yy < 0 || yy > verticalSubdivisions ? 0 : sin * cosSlant,
        yy < 0
            ? -1
            : yy > verticalSubdivisions
                ? 1
                : sinSlant,
        yy < 0 || yy > verticalSubdivisions ? 0 : cos * cosSlant
      ]);

      uvs.addAll([ii / radialSubdivisions, 1 - v]);
    }
  }

  for (int yy = 0; yy < verticalSubdivisions + extra; ++yy) {
    for (int ii = 0; ii < radialSubdivisions; ++ii) {
      indices.addAll([
        vertsAroundEdge * (yy + 0) + 0 + ii,
        vertsAroundEdge * (yy + 0) + 1 + ii,
        vertsAroundEdge * (yy + 1) + 1 + ii
      ]);
      indices.addAll([
        vertsAroundEdge * (yy + 0) + 0 + ii,
        vertsAroundEdge * (yy + 1) + 1 + ii,
        vertsAroundEdge * (yy + 1) + 0 + ii
      ]);
    }
  }

  // Set index buffers and attributes.
  setIndex(indices);
  setAttribute('position', Float32BufferAttribute(vertices, 3));
  setAttribute('normal', Float32BufferAttribute(normals, 3));
  setAttribute('uv', Float32BufferAttribute(uvs, 2));
}