Remove Inner Prim

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Hi,
I need your help in order to solve my problem.
I want to use a voxelization process plus an extra remesh on some object in order to create efficient Mesh LOD
The problem I have is that some object has hole (for example imagine a cube missing its bottom face)
Why: Simply because this object is always stuck in a ground or a building.
The object open, the 2 steps remesh process generate primitive INSIDE my object.
And that’s a problem since this primitive won’t be ever seen and because of extra steps (material baking), this extra primitive will cost a lot of texture space when I will unwrap my UV.
So my goal is to remove this inner primitive.
One solution that I use in an old pipeline was to create extra infinite plane in Simplygon to get of the inner triangle.
Trying to do the same process in Houdini I’ve tested multiple approach with no big success.

One thing that could help me a lot is a feature that will enable me to flag primitive of a geo depending on this primitive is render by a specific camera (fully or partly)
Of course, if a big prim is in front of other, I don’t want the prim deeper in the depth buffer to be mark as render. Just the front one.
Rendering has to be fast with no material. Is there any solution to do that kind of stuff in Houdini ?


With that solution, I will be able to add an extra infinite plane (could be multiple plane as well) run the “mark rendered primitive process” at multiple position and remove the “not marked primitive” and the “infinite plane primitive”


Any idea ?
FRED
Edited by fhoude - Aug. 28, 2019 05:51:40

Attachments:
innerPrim.png (193.6 KB)

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Hey fred,

maybe you could close the mesh before it goes threw your node graph. with a polycap or so. after everything is finished you can remove the capping polygons, by normal or y position…

Cheers
CYTE
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CYTE
Hey fred,

maybe you could close the mesh before it goes threw your node graph. with a polycap or so. after everything is finished you can remove the capping polygons, by normal or y position…

Cheers
CYTE

Thanks CYTE, Yep I already test this approach. Agree I could be an easy win solution but polycap run well on simple object but run “randomly” on my asset. Perhaps I need to better deal with group to limit the polycap on the point/prim close to my plane…
Will run some more test with this node and will let you know !
Cheers,
FRED
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maybe convex hull is a tool that can help. you could create the missing part of the geometry and merge it with your original..
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