function createRenderStates(primitive) {
  if (defined(primitive._rs)) {
    return;
  }

  primitive._rs = getRenderState(false);
  primitive._rs3DTiles = getRenderState(true);
}
Cull front faces of each volume (relative to camera) to prevent
classification drawing from both the front and back faces, double-draw.
The geometry is "inverted" (inside-out winding order for the indices) but
the vertex shader seems to re-invert so that the triangles face "out" again.
So cull FRONT faces.