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In article <39E60BF7.A7CE2A8D@schunter.etc.tu-bs.de>,
chr### [at] gmx de wrote:
> That looks promising, but if i understand things right both blurred
> reflection and transparency are only fakes for rough surfaces (of
> course that doesn't mean they are obsolete)
True, they are intended to simulate evenly rough surfaces. You can get
more precise and controllable results using a normal, but you need
antialiasing to get the effects to be visible, and that affects the
whole scene and is slow.
If I can figure out a way to supersample specific textures or objects, I
will try to implement it...it could use a method similar to the blur
algorithms I am working on now. If I can work out how to get an estimate
of the ray footprint, a sort of imitation differential ray-tracing might
be possible.
> The structures in the second version seem to have some similarities
> with shadows from area lights.
Yes, because the rays "fan out" and are evenly spaced, the spacing gets
larger with distance, similar to the way area shadows spread out.
These artifacts should be less visible with more random backgrounds(the
checker pigment used here really shows the problem because of it's
repetitive nature).
I suppose if the original algorithm is like media method 1, the current
one is like media method 2. I have a couple ideas for anti-aliasing the
blur:
1) Sample along 2 perpendicular directions, like the existing method 2,
but super-sample between two samples when their difference in color
exceeds a threshold. This would be sort of like media method 3...
2) Send rays out in a triangular pattern, dividing into sub-triangles
when necessary. This would have the advantage of covering an area of
space instead of sampling along two directions...the recursive triangle
pattern might make the aliasing less noticeable, too.
> I estimate both algorithms take quite long to render compared to normal
> transparency depending much on what's behind the transparent object.
Compared to ordinary transparency: yes, it is much slower. However, the
second version can sometimes produce smoother results with the same
number of samples than the first version, so the slowdown isn't too bad,
especially if it only covers a small area of the image.
These images both had 12 samples, and rendered in about the same
time(around 2 minutes, though I haven't performed a real test of
rendering speed yet).
> BTW, I remember you working on some pattern blurring function, did
> you have any results in that direction ?
I am planning to make another try, the first one wasn't very successful
or easy to use(it used a 3D convolution matrix, which allowed effects
other than blur, but was a pain to use and too slow with matrices large
enough to get decently smooth blur. I plan to allow this and another,
easier to use and faster method in my next try.). I am debating whether
to blur patterns or pigments...probably both.
--
Christopher James Huff
Personal: chr### [at] mac com, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tag povray org, http://tag.povray.org/
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