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(Sorry for the reposts)
Whilst rendering internal room scenes with plane walls, I have noticed (as have many
others
I'm certain) that using a high error_bound gives better (ie non-blotchy) results on
the large
flat areas, but poor (ie too light) shadows. However, a very low error_bound creates
blotchiness on the large flat areas, but great shadows.
Would it be possible (and I am no expert on how radiosity works) to specify different
values
for error_bound for different areas of the image, and have POV-Ray interpolate between
them to
give smooth transitions? My idea works thus:
Imagine the rendered output as a grid, with <0,0> at top left, and <10,10> at bottom
right.
The user could then say something like:
error_bound_map {
<0,0>,1,
<3.46,2.45>,0.1,
<3.65,2.84>,0.15,
<1.165,9.866>,1.22,
.....
}
POV-Ray could then create it's own array (of user_specified resolution) of error_bound
entries, covering the image.
It would be very helpful if entries could be inserted into the map out of order too,
as and
when the user decides a new entry is needed, rather than having to place them in order
of
numeric value (is that clear?).
This might also help speed-up parts of the image too, I think.
I have no idea if the above is workable, or codeable within the confines of the
current source
code. Maybe in version 4? (or hopefully in version 4, a better quality of radiosity
could be
achieved without the above being neccessary.)
Any comments on this?
All the best,
Andy Cocker
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Andrew Cocker wrote:
>
> (Sorry for the reposts)
>
> Whilst rendering internal room scenes with plane walls, I have noticed (as have many
others
> I'm certain) that using a high error_bound gives better (ie non-blotchy) results on
the large
> flat areas, but poor (ie too light) shadows. However, a very low error_bound creates
> blotchiness on the large flat areas, but great shadows.
>
> Would it be possible (and I am no expert on how radiosity works) to specify
different values
> for error_bound for different areas of the image, and have POV-Ray interpolate
between them to
> give smooth transitions? My idea works thus:
>
> [...]
I'm not sure if that would be useful, but it could be worth testing.
Using a function for the error_bound would probably be better than your
approach.
There is already code increasing the error bound under certain
circumstances:
function 'Compute_Ambient()' in radiosit.cpp:
save_bound = opts.Radiosity_Error_Bound;
if ( Weight < .25 )
{
opts.Radiosity_Error_Bound += (.25 - Weight);
}
/* NK rad 22 Nov 1999 - switched to LayNormal */
reuse = ra_reuse(IPoint, LayNormal, Ambient_Colour);
opts.Radiosity_Error_Bound = save_bound;
So it won't be that difficult to add a function evaluation there. But
don't forget that this could slow down things quite significantly.
Christoph
--
POV-Ray tutorials, IsoWood include,
TransSkin and more: http://www.tu-bs.de/~y0013390/
Last updated 13 Aug. 2002 _____./\/^>_*_<^\/\.______
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"Christoph Hormann" <chr### [at] gmx de> wrote in message
news:3D6F8D1B.24EB0982@gmx.de...
>> I'm not sure if that would be useful, but it could be worth testing.
> Using a function for the error_bound would probably be better than your
> approach.
Ok. How would that work? Would it be automatic, or require user input to tell POV
where you
require a higher or lower error_bound? I don't really understand functions yet.
> There is already code increasing the error bound under certain
> circumstances:
I suppose my suggestion is something of a hack to get radiosity to work in a visually
pleasing
manner (which may or may not be the technically correct manner), but IMHO some scenes
would
definitely benefit from the added control, even at the expense of increased rendering
time.
Andy Cocker
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3d6f88fa@news.povray.org...
> Would it be possible (and I am no expert on how radiosity works) to
specify different values
> for error_bound for different areas of the image, and have POV-Ray
interpolate between them to
> give smooth transitions? My idea works thus:
Sometimes I render the entire image with low rad settings good enough for
most objects in the scene, and then I re-rendering with higher settings the
parts that look ugly (Poser models' faces typically look terrible and
blotchy with low rad settings). After that it's just a matter of cut and
paste. From a practical point of view that's equivalent to having the whole
radiosity block subject to a sort of "map", and the possibility of doing
that in POV-Ray itself would be nice.
G.
--
**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters
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"Gilles Tran" <git### [at] wanadoofr> wrote in message news:3d6fe8e0@news.povray.org...
> Sometimes I render the entire image with low rad settings good enough for
> most objects in the scene, and then I re-rendering with higher settings the
> parts that look ugly (Poser models' faces typically look terrible and
> blotchy with low rad settings). After that it's just a matter of cut and
> paste. From a practical point of view that's equivalent to having the whole
> radiosity block subject to a sort of "map", and the possibility of doing
> that in POV-Ray itself would be nice.
Yes, I had thought of doing this, but was concerned about the possibility of
noticeable
differences around the edges of each rendered section. Do you find these are a
problem?
Andy
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3d6febb6@news.povray.org...
> Yes, I had thought of doing this, but was concerned about the possibility
of noticeable
> differences around the edges of each rendered section. Do you find these
are a problem?
Usually no. In fact I did that yesterday on a 6400 x 4800 render where the
technique saved me a few days (at least). The whole render used
count/error_bound 200/0.05 and the detailed part 1000/0.02. In other cases
where the whole render had used lower settings I may have had to manually
smooth the edges, but nothing important or time-consuming (in Picture
Publisher there's even an option to smooth the borders of the pasted image
automatically).
G.
--
**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters
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"Gilles Tran" <git### [at] wanadoofr> wrote in message news:3d700d8a@news.povray.org...
> Usually no. In fact I did that yesterday on a 6400 x 4800 render where the
> technique saved me a few days (at least). The whole render used
> count/error_bound 200/0.05 and the detailed part 1000/0.02. In other cases
> where the whole render had used lower settings I may have had to manually
> smooth the edges, but nothing important or time-consuming (in Picture
> Publisher there's even an option to smooth the borders of the pasted image
> automatically).
Ok, thanks for the advice Gilles. I shall definitely use this technique on a couple of
images
that I just haven't been happy with.
Andy Cocker
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Andrew Cocker wrote:
> Imagine the rendered output as a grid, with <0,0> at top left, and
> <10,10> at bottom right. The user could then say something like:
It should be somehow relative to the scene space 3d-coordinates, not the
screen 2d-coordinates, or maybe object-specific in some way. Otherwise
you'd have to recreate the map from scratch if every time you move the
camera, not to mention animations...
I'm not the right person to talk about radiosity features though.
Rune
--
3D images and anims, include files, tutorials and more:
rune|vision: http://runevision.com (updated July 12)
POV-Ray Ring: http://webring.povray.co.uk
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"Rune" <run### [at] mobilixnetdk> wrote in message news:3d7150bf@news.povray.org...
> Andrew Cocker wrote:
> It should be somehow relative to the scene space 3d-coordinates, not the
> screen 2d-coordinates, or maybe object-specific in some way. Otherwise
> you'd have to recreate the map from scratch if every time you move the
> camera, not to mention animations...
Yes, of course, you are correct. Object-specific (falling off around the object) would
be
great.
> I'm not the right person to talk about radiosity features though.
Neither am I ;-)
Andy
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Rune wrote:
>
> It should be somehow relative to the scene space 3d-coordinates, not the
> screen 2d-coordinates, or maybe object-specific in some way. Otherwise
> you'd have to recreate the map from scratch if every time you move the
> camera, not to mention animations...
Right, but defining a value on a per object basis is probably pretty
useless since most visible artefacts occur on the surface of one object.
My first tests use a function which works pretty well and is simple to
implement too. :-)
See p.b.i. for an example.
Christoph
--
POV-Ray tutorials, IsoWood include,
TransSkin and more: http://www.tu-bs.de/~y0013390/
Last updated 13 Aug. 2002 _____./\/^>_*_<^\/\.______
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