In article <3ee4fc87@news.povray.org>,
 Lutz-Peter Hooge <lpv### [at] gmxde> wrote:

> Christopher James Huff <cja### [at] earthlinknet> wrote:
> 
> > Actually, it would be more comparable. The isosurface isn't composed of 
> > flat surfaces.
> 
> Here are some pictures to compare the different interpolations in
> isosurfaces.
> <http://www.lutz-peter.hoogi.de/extern/hfield/interp.html>

Normalized distance doesn't work too well for this...interesting result 
on the bilinear, I hadn't exactly expected those patches, though it is 
obvious now that I think about it. They aren't flat, you can see the 
curvature if you have two opposite points "higher" than two others 
(where the isosurface shows its diagonals the most strongly), but the 
discontinuous normal does make them more comparable to an unsmoothed 
isosurface. It is an improvement...I wonder how difficult it would be to 
implement a bilinear patch method for the height field primitive...or at 
least a better smoothing method. The current one looks far from ideal.

What were the render times like?


> I implemented bicubic as a function, however there is still some problem
> with it, causing some artifacts.

It definitely looks the best.


> btw, is there a reason bicubic interpolation isn't in POV?
> Yesterday I succeeded in compiling (Mega-)POV, I think implementing 
> bicubic interp. would be a good exercise.

Only that it isn't implemented. Type 3 is actually "cubic spline", it 
just isn't implemented. Similarly, the supported mappings are plane, 
sphere, cylinder, and torus, but there are declarations in the code for 
parabolic, hyperbolic, and piriform.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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