In article <3d29bcf4$1@news.povray.org>, "Hugo" <hua### [at] post3teledk> 
wrote:

> I'll try again then. I was only talking about the reflection tricks without
> Megapov. Lets say you average 5 normals, using the bump pattern scaled very
> big. Then you have 5 normals, but their directions are random..

Right. It has to be that way, otherwise you wouldn't get blur. The 
problem is?


> Example: You apply the blur texture on a plane and put a white sphere above
> it, that is supposed to be reflected on the plane, and use a black
> background.. The result with 5 averaged normals is not 5 eqaul steps between
> black/white. Because the bump patterns have random values (psudo-random, to
> be precise).

That's why you need much more than 5 samples. The blur patch takes them 
at complete random in the sampling area, so you get a "noisy" result 
where the color of one pixel has little relation to the color of the 
next. With the "average texture trick", the sample directions change 
relatively slowly over space, so the contribution from a specific 
direction is taken into account over an area of the surface, and you get 
a "stepping" artifact instead of noise. The stepping effect is less 
noticeable, so you can often get away with fewer samples...a similar 
situation as with method 1 vs. method 2 or 3 media.

It doesn't look good with only a few samples because you need more 
samples...there isn't really any way around that. It might be possible 
to add a pretrace stage that precalculates the blurry reflection at 
various points and then interpolates that data, similar to radiosity, 
but that would be a major addition...and the existing blur patch doesn't 
do that.

The existing blur patch looks awful with 5 samples, why are you 
complaining about the number needed by the averaged texture technique? 
The current blur patch is not any better!

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

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