Houdini Digital Asset is outputting bad geometry that Maya cannot handle

   405   4   2
User Avatar
Member
3 posts
Joined: Sept. 2017
Offline
Hello forum,

After exporting my hda to Maya I'm getting errors with the generated mesh (this also happens when the mesh is exported from Houdini as FBX).

The error from the Houdini Engine in Mays is like this:

// Warning: Attempted to create 42 polygons, but only 40 polygons were created. // 
// Warning: Attempted to create 244 face-vertices, but only 160 face-vertices were created. //
// Warning: This likely means that the Houdini Digital Asset is outputting bad geometry that Maya cannot handle. As a result, other attributes (such as UVs and color sets) cannot be transferred. //

The error from the FBX import is a bit more helpful:

The plug-in has detected mesh nodes containing polygons with overlapping vertices.

My Houdini asset is very simple, it consists of points, extruded surface and some polybevels.

Any pointers to a fix that produces clean geometry are highly appreciated.

Thanks
Paul
User Avatar
Staff
1447 posts
Joined: March 2012
Offline
Maya, unfortunately, doesn't support polygons with “bridges” to holes, (e.g. attached image). They handle holes as completely separate entities. They also don't support any other sort of polygon with the same point occurring two or more times.

If you can get away with triangulating the geometry (e.g. Divide SOP), that should solve the issue in most cases. For the rest of the cases, after triangulating you'll also need a SOP that removes triangles with the same point two or more times. I can't seem to find where that is at the moment, but the following should work in a Primitive Wrangle:

int pt0 = vertexpoint(0, vertexindex(0, @primnum, 0));
int pt1 = vertexpoint(0, vertexindex(0, @primnum, 1));
int pt2 = vertexpoint(0, vertexindex(0, @primnum, 2));
if (pt0 == pt1 || pt1 == pt2 || pt2 == pt0) {
removeprim(0, @primnum, 1);
}

Attachments:
BridgeToHole.png (49.0 KB)

User Avatar
Member
3 posts
Joined: Sept. 2017
Offline
Thanks for the quick reply.

The divide SOP has already been used and the resulting geometry is a real mess (there are overlapping triangles that show up in renders and impossible to UV map, etc…).

I've slapped the code above onto a Wrangle SOP but it didn't seem to make much difference.

ndickson
you'll also need a SOP that removes triangles with the same point two or more times. I can't seem to find where that is at the moment

Do you mean there's a SOP node that I can use to help with this process?

Thanks
User Avatar
Member
816 posts
Joined: Sept. 2013
Offline
I made an asset that attempts to identify/clean these unsupported polygons. Maybe give it a try and see if it helps.

Attachments:
maya_unsupported_prims.hda (7.0 KB)

Andrew / アンドリュー
User Avatar
Member
3 posts
Joined: Sept. 2017
Offline
Thanks for taking the time. Much appreciated.

However I am nowhere near Houdini right now. Will try your asset as soon as I can and will update my answer.

Thanks again.
  • Quick Links