RE: [Algorithms] Re: Portal VS BSP

[Neil S. <ne...@r0...>]

> I think we classified portal culling (both screen-space 
> axis-aligned as well as 3d) as an "occlusion culling 
> specialization of the
> (hierarchical) view frustum culling algorithm (for fixed, 
> specialized scenes)" in the original dPVS manual (at least we 
> did in the subsequent journal paper), the same way I regard 

That's a bit of a mouthful. :)

> back-face culling to be an "occlusion culling algorithm for 
> closed, watertight objects with limited camera motion" (think 
> a moment about the latter :)). 

Strangely, I don't tend to think of backface culling as a visibility
algorithm, but more as a rasterisation rule that eliminates invalid drawing
of the object's surface which is, after all, a polygonal representation of
the surface of a volume. The back faces of these polygons are not part of
that representation (it is only supposed to work looking from the outside)
and so should be removed.

I don't know if that makes any sense to anyone else, but it lets me sleep at
night. ;)

> I have really nothing important or interesting to add into 
> this conversation, but just wanted to mention that it always 
> confuses the heck out of me when someone starts talking about 
> BSP visibility :)

Yes, that's what perked up my interest, because I've heard people talk about
BSP-based visibility before and I wondered what the hell they were talking
about. Suffice to say, I was a bit disappointed when I found out...

- Neil.