function semanticToVariableName(semantic) {
  switch (semantic) {
    case VertexAttributeSemantic.POSITION:
      return "positionMC";
    case VertexAttributeSemantic.NORMAL:
      return "normalMC";
    case VertexAttributeSemantic.TANGENT:
      return "tangentMC";
    case VertexAttributeSemantic.TEXCOORD:
      return "texCoord";
    case VertexAttributeSemantic.COLOR:
      return "color";
    case VertexAttributeSemantic.JOINTS:
      return "joints";
    case VertexAttributeSemantic.WEIGHTS:
      return "weights";
    case VertexAttributeSemantic.FEATURE_ID:
      return "featureId";
    //>>includeStart('debug', pragmas.debug);
    default:
      throw new DeveloperError("semantic is not a valid value.");
    //>>includeEnd('debug');
  }
}
Per-vertex feature ID.

@type {string}
@constant