Overlapping geometry

[Macha]

Here's a seemingly easy problem but the solution evades me.

I have a bunch of simple shapes (say spheres) copied onto a cloud of scattered points. The resulting geometry has obviously got many many overlapping, intersecting polys. Is there a way to create a clean, yet precise surface out of this? I tried cookie, volumes, foreach, etc but I seem unable to create a simple, clean, light surface out of it.

Any ideas?

[kubabuk]

Have you tried to use an isoOffset sop? I find Minimum mode to work quite well in certain scenerios.

isooffset_geo.hipnc

[Macha]

Have you tried to use an isoOffset sop? I find Minimum mode to work quite well in certain scenerios.

Thanks but I have tried all of these methods before. If you put down a delete node with a box boundary you can see inside the resulting geometry, and it is quite convoluted, especially for more complicated geometry.

I have also tried running each sphere through a foreach sop with an isooffset inside, hoping to get a cleaner volume, but it doesnt help.

The reason I want a clean geometry is because I would like to use a boolean operation on it (to cut through).

If somehow I could find a way to let the isooffset only recognize the very first surface it encounters, and ignore all the inside geometry...

Isoofset with a point cloud is the best so far but the problem with it is that I can't use a negative offset value (why not?), otherwise I could have used it as an input to create a group slightly smaller than the original geometry and use that to delete superfluous points below the surface.

[kubabuk]

Ok, a different approach. It accumulates new element on each iteration and union-cookie it to the the base geometry. The mesh seems to be clean so it is closer to what you are after, I hope... You can get very same result with the feedback sop (proto_install) The difference is that feedback sop is time dependent.

Cheers,

Kuba

accumulate_loop.hipnc

[Macha]

Thanks Kubabuk! Lovely! That works very well indeed.

[johner]

I have also tried running each sphere through a foreach sop with an isooffset inside, hoping to get a cleaner volume, but it doesnt help.

You can use a volume-based approach with the ForEach SOP. Create a volume that is big enough to contain the copied geometry, then successively union in the SDF for each object using a VolumeMix set to Min inside the ForEach loop. Edit: so "Merge Results" is off for the ForEach SOP. Edit again: and oh yeah, isosurface the result

See attached.

union_volumes.hip

Edited December 28, 2009 by johner

[johner]

You can use a volume-based approach with the ForEach SOP.

For what it's worth, I realized you can also do the equivalent pretty easily in VOPs, gaining multithreading and avoiding the ForEach overhead.

union_volumes_vex.hip