Emit from Topology not possible?

[Pancho]

I'm generating a strand tree which gets meshed using the "Create extrusion along strand" compound.

What's strange:

a) I can't emit particles fron this mesh. Even if I copy the Topology and then freeze it, it's not possible.

b) When I export this mesh (obj or lw) I end up with vertices in the wrong place. Hard to tell whether it is extra geometry or just vertices which end up in the wrong spot. In SI the mesh looks o.k.

Anybody an idea what might be wrong?

Cheers
Thomas

[FXDude]

Have you tried poly-reducing or otherwise filtering it first to clean up residual geo info?

[Pancho]

Sounds interesting. Could you shed some light about the filtering stuff? Never heard about it. The mesh itself is pretty much low res. So the amount of geometry can't be the problem.

How could I "clean" the mesh from within ICE or in general?

[Pancho]

Finally got it to work! I need to delete the first strand position in the "Extrusion" compound. Didn't fully understand what the problem might be, but what the heck ...

Thanks!

[druitre]

Thomas, that sounds like FXdude has a point. In Lightwave, I always ran my objects through this thing that came with LWCAD. It checked for double points/polys, scratched polys, corrupted normals, some other stuff I can't remember. Now LW's strong point was that it can very easily create corrupt geometry... but very easily fix it too with this LWCAD tool.

In XSI it's harder to mess up your mesh but if you do, it's harder to fix as well. Model/Modify/Poly.Mesh/Filter Points and setting threshold very low will eliminate double points, same for filter polygon, but I've never found a one-in-all tool that fixes a mesh thoroughly. Sounds like something would be possible in ICE - a bit along the lines of pb_filterenvelopeweights compound where you can set all types of thresholds to filter out deformers above or below certain values for a whole envelope in one go. You run it, freeze the envelope and you're done.

I'm not good enough at ICE to create it though...

cheers, Jasper

[Pancho]

Thanks for the tips!

I guess my misery starts with the fact that my pointclouds's strands do have different strand counts. Unfortunately the "Create extrusion along strand" only works properly with the same strand count. So I need to insert additional segments close to the "root" of each strand. The segments are so close together that I guess they are part of the problem.

I wonder whether anybody came up with a "Create extrusion along strand" compound which works on a cloud with different strand counts and generates UVs. In case anybody has rewritten the compound for this purpose, I would be more than glad if the one could share it.

No idea why the "Create extrusion along strand" works only on strands with the same length!?

Cheers
Thomas

[Mathaeus]

Thanks for the tips!
No idea why the "Create extrusion along strand" works only on strands with the same length!?

Perhaps a similarity with hair systems, where is a kind of practice to keep the same count. It's much easier to run the interpolation later, or 'modulo trick' along vertices of extrusion. You use a fast 'ID to location' or like, instead of re-sampling or distance based querying the entire strand or mesh.
For example, Houdini won't allow to have different count of strand segments, if his hair filler (fur node in H) is used. Modeling workflow in Houdini is also full of intermediate steps, create attribute, delete attribute, run 'polygon doctor' node, and so on and so on.

My wild guess, you already described what happened. Maybe something, somewhere, created a zero length or too small length between vertices, so ICE emitting node wasn't be able construct polygons.