Mike Williams wrote:
> Wasn't it Mike Thorn who wrote:
> 
>>I am cutting a hole in the middle of the whole group of them.
>>
> 
> 
> That'll be what's making it slow. It's the same sort of situation that's
> covered in my holes tutorial <http://www.econym.demon.co.uk/holetut> but
> inside out. One large hole in a union of many small objects, rather than
> many small holes in one large object.
> 
> What happens is that the CSG causes POV to be unable to calculate
> efficient bounding, and ends up putting the whole thing into one huge
> bounding slab. This then means that POV has to test every ray that
> crosses this large bounding slab against every one of the 1024
> superellipsoids. With efficient bounding, there are 1024 small bounding
> slabs and each ray only hits a few of them, so there are only a small
> number of superellipsoid intersection tests for each ray.
> 
> There are two good solutions. That described by Slime (difference the
> hole from every superellipsoid) and the use of a single isosurface (as
> described in my previous response).
> 
> Slime's method works by allowing POV to create a bounding for each
> superellipsoid-minus-big-hole object.
> 
> The isosurface method works by the fact that it is a single object, so
> each ray only needs one intersection test even when the isosurface looks
> like it consists of 1024 smaller pieces.

You're a genius. Or I'm an idiot. Either way, you just slashed my render 
time on that floor from ~4:32 to ~35sec. Wow.

Thanks a million...you don't realize what saving that much time means to 
me, and after seeing a few of the things on your website that one can do 
with an iso, I'm now a big fan of them. Too bad math is my personal 
archenemy.

Speaking of bounding, I've heard that POV's bounding isn't always as 
efficient as it could be. Would it be worth my while to manually bound 
every object in my scene, or would it be too much trouble for minimal gain?

Every time I sign on to this board I realize just exactly how much more 
I belong in .newusers than anywhere else. :) You guys are great. Thanks 
again.

~Mike

Post a reply to this message