[Sidefx-houdini-list] random fur scale

Pablo Giménez pablogipi at gmail.com
Mon Feb 11 19:31:36 EST 2008


2008/2/12, Ivan DeWolf <ivan at martian-labs.com>:
>
>
> actually, VEX usually executes faster than c++ code, unless you spend as
> much
> time optimizing your code as SESI did optimizing VEX. The SIMD
> architecture
> lines the data up niceley for the CPU, but it's a friggin nightmare to
> think it
> through as a human being.


Good to know tha thge optimizer is so good, we can begin an old discussion
about what is fastes shaders in a language shader (renderman/mantra) or in
c++ (mentalray) ....

the volumetric system in Houdini is actually wicked fast- I've written my
> own in
> VEX before and in c++. Both were a LOT slower. There's definiteley a ton
> of
> optimization going on in there, probably in the c++ code and how it uses
> the
> VEX you write...


And yes the volumetric stuff is more times faster now with the new metaballs
functions for VEX but still very very slow compared with soutions like Fume.

Quoting Pablo Giménez <pablogipi at gmail.com>:
>
> > 2008/2/12, Fred Valleur <fred.valleur at gmail.com>:
> > >
> > > Hi,
> > >
> > > a CVex shader is called from a compiled  C++ dso (or dll on windows).
> It
> > > is
> > > written in VEX and let you modify data used by the compiled plugin. It
> > > offers great flexibility as you don't have to "hard-code" everything
> in
> > > C++.
> > > The fur SOP/Geometry shader  is a good example to look at. The hair
> > > generation and memory allocation is handled by the C++ plugin, but it
> > > calls
> > > two CVex Shaders that can modify hair/points attribute to change the
> look
> > > of
> > > the fur.
> >
> >
> > I am guessing here but ... maybe this can be used to speedup
> volumetrics, do
> > all the raymarching hard stuff in C++, more times faster than VEX, and
> use
> > VEX only to modify every step sample.
> > The raymarching loop and some fancy adaptative step formula can be done
> in
> > c++, only guessing.
> >
> > This way, you can write your own kink/frizz funtions in VEX  and let the
> C++
> > > code handle the "low level" hair generation.
> > >
> > > Hope this makes it a bit clearer,
> > >
> > > Cheers,
> > >
> > > Fred.
> > >
> > > --
> > > Frederic Valleur | LaMaison
> > >
> > >
> > > >Hi guys,
> > >
> > > >Sorry to hijack. Could someone just quickly explain what a CVEX
> shader
> > > is?
> > > >Not heard of this before. I take it it's different from a VEX shader?
> Is
> > > >is a compiled version? What situations would you use it for?
> > >
> > > >Thanks
> > >
> > > >Andy
> > > _______________________________________________
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> > > Sidefx-houdini-list at sidefx.com
> > > https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> > >
> >
> >
> >
> > --
> >
> > Un saludo
> > Best Regards
> > Pablo Giménez
> > _______________________________________________
> > Sidefx-houdini-list mailing list
> > Sidefx-houdini-list at sidefx.com
> > https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >
>
>
> -Ivan
>
> ---------------------------------------------------------
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> -Yvon Chouinard
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>



-- 

Un saludo
Best Regards
Pablo Giménez



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