6.4 Occlusion and light-tight bodies
The simulation renders a depth map per projector, so anything in the way casts a real shadow — a truss, a column, a person-sized box.
Bodies are light-tight per projector: each machine lights only the face turned toward it, and you see that light only from the same side. Rear-projection screens opt out. The rule does not depend on which way a surface normal happens to point, which is what makes it safe on imported venue CAD, where normals are often inconsistent.
Openings need no special handling for the same reason. Cut a doorway (§3.14) and the light goes through it, the wall beside it still shadows, and the bright rectangle lands on the floor beyond — a hole is an absence of triangles, and the depth map simply does not find one there.