A beginner BSP question...

Are you sure the wall you''re talking about is actually used as a dividing plane? If not, even if it spans both sides of some other wall it won''t have to be split.

I happen to have that book right here, and...

D does show up in the BSP, as the front child of C. But maybe I''m misinterpreting what you''re saying.

But, to answer your question. In this case, C is picked as the first splitting plane. This gives us two half-spaces, and two new sets of polys, B and AE on one side and D on the other.

A poly can only split another poly in its own half-space. D is the only poly in its half-space, so it doesn''t split any other polys. On the other side we have the polys AE and B. If AE had been chosen (rather than B) as the splitting plane, there would be no further splits. Since B is chosen, it splits AE into A and E. Note, however, that B bisects, but does not split, C. This is because B can only split polys in its own half-space, and C is not in its half-space.

Hmm. This stuff is a little hard to explain. Did that help at all?

I think I get it... Basically, if you have a wall A, and it''s left subspace contains B, C, and D... Regardless of whether B,C, or D bisect A, they cannot split it since it is not really in their space... They are in ITS half space...

Tony

"I think I get it... Basically, if you have a wall A, and it''s left subspace contains B, C, and D... Regardless of whether B,C, or D bisect A, they cannot split it since it is not really in their space... They are in ITS half space..."

Correct.