[Sidefx-houdini-list] baking coverage into point particles

Michael K. O'Brien mobrien at pixar.com
Thu Dec 10 11:28:46 EST 2009


>-- On Thu, Dec 10, 2009 at 07:12:42AM -0500, Mark Elendt wrote:
> On Wednesday Dec 09 at 22:00, Michael K. O'Brien wrote:
> > I have a set of semi-transparent points (disks) and a light. I'd like to
> > bake the visibility of the points as seen from the light. Basically, I want
> > to project a ray from each point to the light and sum up the transparency as
> > I go. Is there a way to do something like that in Houdini?
> Isn't this a deep shadow map?  

Sort of. A deep shadow map is a projection (from the light) of functions of
visibility (probabilities of visibility). I want the result of that lookup
baked into my geometry.

> Or do you need it geometrically?
> If you have a DSM/DCM, you should be able to sample the data in a VEX
> SOP.

That sounds promising, I'll have to figure that out. I'm not really all that
familar with Mantra. Are there any things I need to worry about?

> There may be other solutions (with either VEX ray-intersection (yes
> there is ray intersection in SOPs) or the Ray SOP).
> How many points?

100k ish.


> -- 
> Mark Elendt
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Michael O'Brien                                                         Tools
Pixar                                                       mobrien at pixar.com

Censorship is the mother of metaphor.
                            -Jorges Luis Borges

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