[Sidefx-houdini-list] random fur scale

Pablo Giménez pablogipi at gmail.com
Tue Feb 12 10:15:57 EST 2008


2008/2/12, Olex P <hoknamahn at gmail.com>:
>
> I mean BSP, Octree, kd-tree etc.


Ah! ok.

On Feb 12, 2008 12:58 PM, Pablo Giménez <pablogipi at gmail.com> wrote:
>
> > 2008/2/12, Olex P <hoknamahn at gmail.com>:
> > >
> > > Language doesn't matter (almost doesn't matter). The main speedups can
> > > give
> > > difference in architecture and used algorithms. For example
> raymarching
> > > written in Python using tree structures could be faster than C++
> > > raymarcher
> > > without trees.
> >
> >
> > Sure, but usually c, c++ code should be faster only because is a lower
> > level
> > than other languages.
> > And can you talk more about tree structures appplied ti volumetrics?
> > Thanks
> >
> > On Feb 12, 2008 12:31 AM, Pablo Giménez <pablogipi at gmail.com> wrote:
> > >
> > > > 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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> > > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > --
> > > > > >
> > > > > > 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
> > > > >
> > > > > ---------------------------------------------------------
> > > > > "Perfection is achieved when nothing else can be removed"
> > > > > -Yvon Chouinard
> > > > > _______________________________________________
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> > > > >
> > > >
> > > >
> > > >
> > > > --
> > > >
> > > > 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
> > > >
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> > >
> >
> >
> >
> > --
> >
> > 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
> >
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-- 

Un saludo
Best Regards
Pablo Giménez



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