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group of inside face


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I'm a new user. I'm testing some RDB stuff on Houdini. I imported a simple GEO shattered in Max. RDB works fine. Now, I'd like to group inside faces of my OBJ to made a debris system but I don't find the method. Maybe I'm thinking of a "distance test" expression (faces that I want to select are overlapped...) and I tried to group some points or primitive based on distance...but without results. (maybe with distance() expression).

Could you help me, I'm becoming mad !

Thanks in advance

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If you have the original (unshattered) geometry you could use the ray SOP.

Plug the shattered geometry into the first and the original geometry into the second input.

Uncheck "Transform Points" and check "Point intersection distance". This will add an attribubute "dist" to your geometry containing the distance to the closest primitive in the direction of the point normal

Since all your inside polys are usually quite a distance away from the hull of the unshattered object you can group them easily based on a simple threshhold expression.

Hope that helps

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The easiest is to create the inside group when you shattered the object in Max. To deviate from RichieMayor's method, you don't have to use the Ray SOP or compute distance. Just take the original unshattered geometry, scale it down slightly and connect it to the second input of the Group SOP and use it as a Bounding Object. Do this before the geometry goes to DOPs and the groups will remain through the simulation.



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