Forelevel

Stage has three levels: low forelevel in front of curtain for Narrator, main level for most of the action, slightly higher level for the balcony.

The parasphenoid bears a large cultriform process; the anterior end of the process is truncate and lies at the forelevel of the orbit.

The edge points generated by subdivision are only affine combination from the vertices of fore-level, and these vertices are vertex points in this level.