Sharp edges

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Does anyone know a way in Houdini to keep my sharp edges with and FBX import from Softimage, but not "cusp" or cut the edges so I end up with separate poly islands ? It messes up the geometry and the point count.

Thanks,

R
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without file it's difficult to see what your problem is
but essentially you need vertex N, which either comes from your fbx and in that case you should already see it correctly
if not you can also recreate using Normal SOP or other methods, but ideally it'd just come in on import
Tomas Slancik
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Thanks for the quick reply.

The problem is that I have a lot of geo with "hard" edges in Soft I'd like to import into Houdini.

I don't know about any "vertex N" but no matter what I do, whenever I import the geometry, Houdini keeps adding a "soft edges" that "cusps" or "splits" the edges or vertices. The "edges cusp" SOP has a "cut Boundary Points" option that sounds like enabling or disabling splitting the vertices, but dis- or enabling it has no effect whatsoever.

What I'm looking for is a way to at least keep my hard edges as a group without the geo being altered, or having to copy / paste the edges into a group SOP manually for every object.

To be honest, it slowly starts to smell like the only way to import or add sharp edges in Houdini is to actually split them. Which seems a little backward in in my opinion.

Thanks,

R.
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Houdini can represent hard edges just fine without splitting points. As tamte was saying your FBX should be exporting vertex normals, meaning they should be a vertex attribute, not a point attribute.
Typically this should all just work, do you have an example file?
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DaJuice
Houdini can represent hard edges just fine without splitting points. As tamte was saying your FBX should be exporting vertex normals, meaning they should be a vertex attribute, not a point attribute.
Typically this should all just work, do you have an example file?


Maybe the FBX importer is buggy then.

When I import an object with hard edges from XSI an "edge cusp" is added that splits all hard edges :

On the left XSI cube with hard edges, on the right the imported FBX in Houdini with an exploded view to show the issue.

FBX : https://www.dropbox.com/s/7dh0gvywlf9vf65/Cube_edges.fbx?dl=0 [www.dropbox.com]
Edited by toonafish - Oct. 12, 2021 18:17:36

Attachments:
edges.jpg (73.7 KB)

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toonafish
When I import an object with hard edges from XSI an "edge cusp" is added that splits all hard edges
yes, maybe that's some kind of leftover from old times
but if you bypass or delete that EdgeCusp node, all should be fine, the vertex N in your fbx file seems to properly create sharp edges
Tomas Slancik
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Meh, I wish.

When I delete the "edge cusp" and export back to FBX the normals are broken and I lost my "hard edges".

Maybe it would help if the Houdini FBX exporter would export edge- or poly groups, but also no cigar so far.

But thanks for the help.

R.
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toonafish
Meh, I wish.

When I delete the "edge cusp" and export back to FBX the normals are broken and I lost my "hard edges".

Maybe it would help if the Houdini FBX exporter would export edge- or poly groups, but also no cigar so far.

But thanks for the help.

R.

Probably because there is no such thing as a hard edge in Houdini. There's no way to represent such and so it can't be exported. Hard edges can either be represented as unshared points or with vertex normals.
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Hello @toonafish,
Instead of edgecups node you can add a normal sop with same edges selection and set normal to 0.
As @jsmack said there is no "hard edge" in houdini like in softimage but finally it's just a way softimage have to force normal to hard (0) on specific edges.

Also note that normal sop as an option (Weighting Method) "By Face Area" that hasn't softimage and compensate a lot !

Hope that help.
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