Hugo wrote:
> 
> I don't know, but I imagine that each call to the isosurface during
> calculation of reflection, refraction, finish, radiosity, lightsources - all
> causes the isosurface to be evaluated again and again.. Similar with
> primitives, but even the fastest isosurface is much slower than a primitive,
> hence the big slowdown.. This is my theory - not necessarily the fact.. IF
> it works like that, then I have to say, a much better idea would be to
> calculate the surface *first* once and for all, and *then* do all the rest
> of calculations.

You are right that isosurface intersection calculation are quite
computation intensive, but the relative slowdown because of reflection,
refraction, radiosity etc. should not be much larger.  Note that i'm not
talking about meshes, heightfields and optimized combinations of shapes,
just comparing basic shapes with isosurfaces.

And if you try an isosurface superellipsoid and a native one and compare
the results you will also see that the isosurface can be much faster.

I agree that there are quite a lot of possibilities to improve isosurface
intersection calculation like precalculations or caching of function
values, but don't forget that one enormous advantage of isosurfaces
compared to meshes for example is the low memory use.

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 18 Mar. 2002 _____./\/^>_*_<^\/\.______

Post a reply to this message