[Sidefx-houdini-list] delayed load points inheriting attributes..?

Sean Lewkiw Sean.Lewkiw at cis-vancouver.com
Wed Mar 9 21:18:01 EST 2011


Some notes on this...

Jeff's notes:  http://www.sidefx.com/index.php?option=com_content&task=view&id=1050&Itemid=216

You can only apply shaders at the OBJ level if you want to use the instancepoint() expression. This makes it difficult to apply multiple textures and lighting models to an object. To get around this, assign attributes to the geo and use these to select textures/mattes/lighting models etc. in the shader.

Velocity attribute motion blur built into a model will not be additive with object level blur. Therefore, if you want both deformation and transformation blur, you will need to not use velocity blur at the object level. This is problematic if you have a particle system with a changing point count, (most particle sims!) To work around this, re-order your points using CHOPs.

Sean





-----Original Message-----
From: sidefx-houdini-list-bounces at sidefx.com [mailto:sidefx-houdini-list-bounces at sidefx.com] On Behalf Of Premamurti Paetsch
Sent: Wednesday, March 09, 2011 5:15 PM
To: sidefx-houdini-list at sidefx.com
Subject: Re: [Sidefx-houdini-list] delayed load points inheriting attributes..?

There's the instancepoint() expression that returns the point number you
instanced onto at render time.
So you might be able use something like: point("/obj/instance_on_me/",
instancepoint(), "id" , 0 ) to return per-point attrs and and pass that on
to your shader interface.
Not sure how this would perform though...

cheers,
prema

On 10 March 2011 06:32, Szymon Kapeniak <szymon.kapeniak at gmail.com> wrote:

> Hmm, I would say that properties won't be passed to archive shaders...
>
> This is fairly simple as long as you have a single shader per baked
> geometry, since you can apply it on instancing point, not instanced
> archive (by using MaterialSOP with overrides).
>
> Once you want more then a single shader per instance, you need to bake
> them into archive IFD, and from now on AFAIK you can't inherit point's
> attributes to be passed  to DL shaders. Or I'm missing something
> also...
>
> I don't think there is any elegant way for doing this other than
> cleverly baking shaders for your archive with varying parameters
> already in place.
>
> Some solution would be to open geometry of instancing points in an
> archived shader and import your attributes by hand from there (far
> from elegance I suppose).
>
> Another idea I used to think of was a custom VEX function returning
> value from a database during render time. As it would be a vex
> constant, performance should not be an issue I believe).
>
>
> cheers!
>
> 2011/3/9 Andrew D Lyons <tstexture at gmail.com>:
> > It's been a while since I looked at this (circa v9.0 alpha) but my
> > understanding is that properties were the means to pass this stuff on
> > nowadays.
> >
> > http://www.sidefx.com/docs/houdini9.5/shade/properties
> >
> > Cheers
> >
> > On 9 March 2011 10:04, Ben Frost <benfrost3d at gmail.com> wrote:
> >
> >> hello all..
> >>
> >> does anyone know how, with a Mantra Delayed Load and  instancing (ie
> rand
> >> animating geo loads per point)..  is it possible for the dynamically
> loaded
> >> geometry to inherit the points attributes inorder to be passed to a/the
> >> shader..  ie, Cd, id, and other custom attributes for arbs..
> >> only finding hacky ways at the moment..  and I'm figuring there is a
> simple
> >> way or something I'm missing...
> >> if any one has come across this before and has any suggestions that's be
> >> awesome..
> >>
> >> cheers
> >>
> >> ben...
> >> _______________________________________________
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> >
> >
> >
> > --
> > =======================================
> > Andrew D Lyons | Digital Artist | http://www.tstex.com
> > =======================================
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