[Sidefx-houdini-list] VOPs question

Andrew D Lyons tstexture at gmail.com
Tue Jun 24 20:34:05 EDT 2008


Just curious -
Has anyone looked at the co-shader support (prman 13.5 shader classes)
in H9.5 shops? Not sure if there is a Mantra support for the idea at
this point, but are shader classes another mechanism to consider?
Cheers


2008/6/24 jiversen <jiversen at rhythm.com>:
> Ah - it went something like this:
>
> *Me:
>
> *I was thinking about PBR and I remember the few weeks it its wee Alpha
> days when it was a whole separate BSDF shading context, alongside
> Surface and Displacement shaders. Then it was combined into the Surface
> shader context and it became a lot easier to use because the shader
> could optimize for the Cf/Of/Af code path in one phase of the rendering
> and for F in another phase .
>
> Why don't we do the same for Displacement now? Wouldn't it make sense,
> now that the technology to do so must be there? I can imagine that it
> would would make a lot of sense to be able to build VOPs which also
> perform displacement (think of a Rust VOP, for instance) and so the
> desire to have linkable shaders similar to mental ray's Phenomenon
> becomes far less desirable. The dimport() function would be called
> implicitly, I suppose, when the surface and displacement contexts use
> the same [varying] variables.
>
> What do you think? Personally I've always just regarded the split
> between Surface and Displacement a necessary evil. I don't think anyone
> wants to work this way, really. It's a limitation forced on us due to
> architecture issues and I don't think it really beneficial to maintain
> the split if we could possibly avoid it.
>
> Thanks,
> Jason
>
>
> *Mark Elendt:*
>
> Ah, but you're asking why don't you bundle the two shaders together into
> a single, shall we call it, a material shader?
>
> Yes, that's an option... And it might even lead to some nice automatic
> optimizations where we can cache computations between shader  runs... Or
> do other magic stuff behind the scenes.
>
> OTOH, I do like to be able to combine a fractal dent shader, on
> arbitrary surface shaders.
>
> If everything were VOPs it might not be as big an issue... But it
> certainly would change the shading workflow Smile
>
>
> *Me:
>
> *Unless, of course, you were thinking of allowing shaders to be chained
> one day anyway Wink Then you could add "deformer"-type displacement
> shaders (like the Fractal Dent) to your heart's content. You could still
> much very anticipate using the current Materials "context" for
> switching/blending/layering shaders and for applying properties.
>
> Yes, it would seem like it might type a change to the workflow- but I
> think it would improve it for real shot work since you don't have to
> maintain two shaders, and all that that entails. It'll be a little
> strange for those testing scenes where you're used to throwing on some
> arbitrary displacement onto a plastic sphere - but very useful when
> developing an ice bridge shader or something.
>
>
> Jerry Corda-Stanley wrote:
>> I'm getting...
>>
>> "The topic or post you requested does not exist"
>>
>> on that link.
>>
>>
>> ----- "jiversen" <jiversen at rhythm.com> wrote:
>>
>>> It's for this that I pimp this idea:
>>>
>>> http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=10237
>>>
>>> Combining all the shading contexts into a single "material shader",
>>> where the surface, displacement and bsdf outputs are automatically
>>> extracted on demand. All the optimizations (like dimport()ing stuff to
>>>
>>> minimize recomputation) would be handled internally without your
>>> knowledge.
>>>
>>>
>>>
>>>
>>> Andrew D Lyons wrote:
>>>
>>>> Ah - nice solution...
>>>>
>>>> Thanks!
>>>>
>>>> 2008/6/19 Peter Bowmar <pbowmar at gmail.com>:
>>>>
>>>>
>>>>> The "correct" way (I use the term Correct very loosely here) would
>>>>>
>>> be
>>>
>>>>> to create the pattern in the Displacement shader, then use
>>>>>
>>> "dimport()"
>>>
>>>>> to import the values in the Surface shader. That way the pattern
>>>>>
>>> code
>>>
>>>>> runs once, saving a lot of computation time.
>>>>>
>>>>> Having said that, I like the HDA suggestion, so you have as much
>>>>> "generic" code as possible inside HDAs that are easy to update as
>>>>> needed.
>>>>>
>>>>> Cheers,
>>>>>
>>>>> Peter B
>>>>>
>>>>> 2008/6/19 Andrew D Lyons <tstexture at gmail.com>:
>>>>>
>>>>>
>>>>>> You could make a VOP subnet HDA and us that in both - assuming
>>>>>>
>>> you
>>>
>>>>>> were ok with constant args to all parms inside the  subnet.
>>>>>>
>>>>>> 2008/6/19 Phil Spicer <PSpicer at bournemouth.ac.uk>:
>>>>>>
>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> Is there a way to import a vop network into another context? For
>>>>>>>
>>> example if I were to create a simple pattern surface and then wanted
>>> to import that pattern into a displacement shader so that it was
>>> dynamically linked, how would I go about it? Is there an Object Merge
>>> SOP equivalent in VOPs?
>>>
>>>>>>> Kind regards,
>>>>>>>
>>>>>>> Phil.
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
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>>>>>>>
>>>>>>>
>>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
>>>
>>>>>>>
>>>>>>>
>>>>>> --
>>>>>> =======================================
>>>>>> Andrew D Lyons | Digital Artist | http://www.tstex.com
>>>>>> =======================================
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>>>>>>
>>>>>>
>>>>>>
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>>>>
>>>>
>>>>
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-- 
=======================================
Andrew D Lyons | Digital Artist | http://www.tstex.com
=======================================



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