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ryan constantine wrote:
> are there good shader tut's out there? urls anyone?
Here is link to one SL tutorial:
http://minerva.ca.scad.edu/faculty/kesson/CA301/shading/surf.htm
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"Vahur Krouverk" <vah### [at] aetec ee> wrote :
>
> I guess that those, who use POV-Ray, should be able to read it without
> problems.
So if I spend the time to learn shaders, is it likely that in the future
there will be an effort to include renderman standards in the official
Pov-ray? Or would I be learning for the patch and nothing else?
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Bill DeWitt wrote:
>
> "Vahur Krouverk" <vah### [at] aetecee> wrote :
> >
> > I guess that those, who use POV-Ray, should be able to read it without
> > problems.
>
> So if I spend the time to learn shaders, is it likely that in the future
> there will be an effort to include renderman standards in the official
> Pov-ray?
This should be asked from POV-Ray team, as I don't have enough authority
to comment on this one. But I do hope that this happens sometime in
future.
One problem could be legal issue: can freeware (such as POV-Ray) use
language, which is used and created for commercial program? I know, that
there is effort to make GPL-ed RenderMan implementation and several
other implementations are available and I hope, that Pixar will not put
it's hand on way, but there is always possibility, that money will talk
louder than common sense. So far, so good...
> Or would I be learning for the patch and nothing else?
Why nothing else? Learning per se is good thing ;o) I personally have
learned great deal of CG stuff (and other things) during creation of
this patch, so at least one person has already benefitted from this
patch. Using Shading Language is good for profound knowledge of CG.
I personally don't think, that Shading Language _itself_ is complex,
especially for those, who know C and CG basics. But _creating_ _good_
shaders is quite complex and knowledge demanding task and not for
everyone. One has to know math (geometry, differential analysis for
antialiasing), physics, optics etc.
This is the reason, why I want to make POV-Ray support for it as
compatible as possible to RenderMan's standard: this way POV-Ray users
can reuse existing and available shaders by modifying only shader input
parameters, which shouldn't be more difficult, than specifying
parameters for some POV-Ray feature (such as radiocity). And advanced
users can tinker with shader code...
Knowing shading language and using it in POV-Ray makes transition to
real-production programs (such as RenderMan, BMRT, RenderDotC) a little
bit easier if someone wants to move from POV-Ray to professional CGI
world. RenderMan interface is flexible, powerful and (unofficial)
standard in CGI.
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Vahur Krouverk wrote:
> I really hope, that this patch is useful for someone and not very much
> of bugs is left there...
Duh, there are bugs and nasty ones, which will crash POV-Ray ;-(
I've updated Windows binaries and source code to avoid this. So, if
someone has problems with POV-Ray crashing during rerendering, when in
previous render shader parameters were incorrectly specified, then fixed
version is available. Linux version will be updated soon. Sorry about
this.
Additionally I've noted, that shader loading and calling counters are
not reset between renderings, but hopefully this is not a problem for
now.
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Pabs wrote:
>
> Vahur Krouverk wrote:
>
> > You read documentation, didn't You?
>
> Obviously not well enough :)
I thought, that there is problem in documentation: my English is not
good enough and documentation could be understood incorrectly...
> Perhaps you could have a system similar to photon mapping where you can ask POV
> to compile the shader (call povslc) to a file if it has not been compiled
> previously.
This automatic compilation would be nice addition, but probably not
trivial one. But I think about it.
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Vahur Krouverk wrote:
> Pabs wrote:
> > Vahur Krouverk wrote:
> > > You read documentation, didn't You?
> >Obviously not well enough :)
> I thought, that there is problem in documentation: my English is not
> good enough and documentation could be understood incorrectly...
I only skimmed the docs - after looking properly at them they were easily
understandable.
-
Bye
Pabs
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Vahur Krouverk wrote:
>
> Hello!
>
> Finally I've decided to release my custom patch of POV-Ray, called
> POVMan.
I "only" discovered it today, and all I have to say is : GREAT !!!
Thank you very much for doing that, it will be highly useful !
(now, the "but BMRT has shading language" argument is down :-))
Fabien.
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Well! Looks like there's a *lot* of interest in this particular patch!
I, for one, rejoice--I have long wanted a version of POV with the
renderman shading language. Great job, Vahur Krouverk! :) And thank
you!
--Richard Adams
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Fabien Mosen wrote:
>
> (now, the "but BMRT has shading language" argument is down :-))
Not quite: mr. Gritz has several times (1)emphasized the importance of
analytical antialiasing (which requires surface derivatives) and POVMan
doesn't support it. Yet.
______________________________________
1)he wrote in c.g.r.r:
===8<=8<========
This is really the crux of the issue. Writing a simple compiler
and interpreter is not all that hard. Writing a renderer that
has all the internals to support the fancy(*) parts of Shading
Language is nontrivial.
(*) By fancy, I mean features that aren't used in "plastic" or any of
the 14 naive required shaders listed in the RI spec, but which are
*mandatory* for absolutely any real-world shader. Among other things,
these would include: derivatives, area operators, named coordinate
systems, (automatically) filtered texture lookups, automatically
interpolated user vertex variables (for reference meshes and such),
illuminance loops to allow custom local illumination models, and
message passing between different shader types (especially between
lights and surfaces).
===8<=8<========
Sigh, long way is ahead: my patch currently supports illuminance loops.
Derivatives and filtered texture lookups hopefully sometime in future...
Message passing in limited extent is probably also possible...
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Hello!
I've updated my download page with new binary and source codes, which
should fix crashes during rerendering. Additionally, as it was noted,
bison gave error on grammar file and I've updated grammar file as well
for those, who want use bison.
As a bonus (for Your patience;-), I've created new examples page, which
contains one example (so far): cloud shader. Address is as follows:
http://www.aetec.ee/fv/vkhomep.nsf/pages/shdrex
It contains sample picture and source code for shader and POV-Ray scene.
It is product of some tinkering and therefore quality is not very good,
but if someone has time and wish to play with it, then this could be
used as starting point...
If I have more time, then I try to create some tutorial pages, which
show some commonly used techniques in shaders...
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