In article <3ee693b7$1@news.povray.org>,
 Lutz-Peter Hooge <lpv### [at] gmxde> wrote:

> > I'd just use type 3 for bicubic. If something else was originally 
> > planned, it was so long ago that it makes no difference, and it fits in 
> > with existing ones nicely.
> 
> Then IMHO CUBIC_SPLINE should be renamed to BICUBIC. 
> (Or BILINEAR to LINEAR_SPLINE)

Well, it's not used anywhere, so might as well.


> > Are those coefficients random?
> 
> No, they are those used in the patch.
> 
> You get them by putting constraints to the cubic function,
> then solving for the cofficients.

Hmm...I was looking at it as something similar to a convolution matrix, 
and expected something symmetrical. I'll have to look at the code to 
figure out what the pattern is.


> > Maybe this would have some use, but can't think of any. Any special 
> > effects this makes possible?
> 
> At least it should be possible to replicate linear and quadratic
> interpolation with it.

But a direct implementation would be faster, right?


> But I think it is also possible to modify the matrix to get a sharper
> image (with the tradeoff of getting more grid artifacts)

That may be useful, but I personally think if the image is low-res 
enough for that to be an issue, a higher resolution image is the best 
solution. You could use a more computationally intensive algorithm to 
resize it outside of POV and use one of the cheap ones for rendering.

-- 
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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