Hi All

Head modeled in Silo, veins added in ZBrush 2 this image is at subdivision
5. I also made a copy at subdivision 7 which produced a 750mb obj file -
3DWin and Pov coped easily but my system struggled, for instance, it would
not let me load the inc file from 3DWin into the Pov editor as there was not
enough memory. Normally such output would be in the form of a displacement
map and a low res mesh( the way the pros are moving) but Pov does not
support subpixel displacement maps.
Meshes at subdivision 7 can hold amazingly intricate detail but I'll have to
wait a few more years before I use it in Pov!

Mick

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news:407fb42d@news.povray.org...
> Meshes at subdivision 7 can hold amazingly intricate detail but I'll have
to
> wait a few more years before I use it in Pov!

Nice. It's good to see non-Poser human modeling slowly but surely coming to
POV-Ray, be it in Silo, Moray or Wings.
The 750 Mo obj is much too big I think. While it's obviously caused by the
subdivision, there should be a way to subdivide only the zones that requires
it. I have little experience with this yet, but modelers often support this
feature.

G.

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ZBrush used to support selective subdivision but I can't find it in ZB2 I'll
have to visit thre forums and see.
Yep 750 is way to large but with displacement mapping one can use models of
only a few thousand polygons!
Dream on - AFAICT only Maya currently supports it though Lightwave have it
in the pipe line. Cinema4? Gilles.

Mick

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Mick Hazelgrove wrote:
> 
> [...]  Normally such output would be in the form of a displacement
> map and a low res mesh( the way the pros are moving) but Pov does not
> support subpixel displacement maps.

???

POV-Ray is a raytracer and whatever program you saw advertising itself 
being capable of doing 'subpixel displacement mapping' surely wasn't 
one.  A raytracer doing on-the-fly displacement of a mesh does not even 
know it it is 'subpixel' or not.

I don't see any problem rendering a 750 MB mesh if you have enough 
memory.  But of course such a large mesh for a simple head is quite too 
much, as Gilles said an adaptive subdivision would be the way to go.

Christoph

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POV-Ray tutorials, include files, Sim-POV,
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news:c5p73s$a7n$1@chho.imagico.de...
> POV-Ray is a raytracer and whatever program you saw advertising itself
> being capable of doing 'subpixel displacement mapping' surely wasn't
> one.  A raytracer doing on-the-fly displacement of a mesh does not even
> know it it is 'subpixel' or not.
>

Very possibly, Mick just meant that certain renderers (and 3D hardware) now
support a form of displacement mapping that is associated with on-the-fly
subdivision/tesselation/whatever, so that one can use low poly meshes and
"shape" them with maps. See for instance:
http://www.edharriss.com/tutorials/tutorial_xsi_text_displacement_map/extrusion.htm
http://www.rhythm.com/~ivan/dispMap.html
Other renderers (such as C4D) only displace the existing geometry so that
any necessary subdivision has to be done (selectively if possible) before
displacement by the user.

G.


-- 
**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters

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Gilles Tran wrote:
> 
> Very possibly, Mick just meant that certain renderers (and 3D hardware) now
> support a form of displacement mapping that is associated with on-the-fly
> subdivision/tesselation/whatever, so that one can use low poly meshes and
> "shape" them with maps. See for instance:
> http://www.edharriss.com/tutorials/tutorial_xsi_text_displacement_map/extrusion.htm
> http://www.rhythm.com/~ivan/dispMap.html

I know what subdivision and displacement mapping are, but that's 
completely different in a raytracer than in a scanline renderer.  What's 
commonly advertised as 'subpixel displacement mapping' is simply not 
just drawing the large triangles on the screen but subdividing and 
displacing them until their size is smaller that that of the pixels of 
the resulting image and then drawing them.

In a raytracer you have to choose a subdivision depth a priori, you can 
try to do this adaptively depending on the distance from the camera but 
this won't work for indirect rays (reflections etc.)  Also note that 
depending on how much memory you reserve for caching the subdivision 
data you may have to subdivide every triangle visible more than once. 
In the end an already displaced mesh (as long as it fits into memory of 
course) will probably always be faster in a raytracer than a 
displacement at render time.

> Other renderers (such as C4D) only displace the existing geometry so that
> any necessary subdivision has to be done (selectively if possible) before
> displacement by the user.

This is already possible in POV:

http://jgrimbert.free.fr/pov/patch/tessel/index.html

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 21 Mar. 2004 _____./\/^>_*_<^\/\.______

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Before this argument gets out of hand :-) I thought I would pass on the fact
that Zbrush can do adaptive subdivision so look out for more highly detailed
and reasonable sized heads!

Mick

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