I have a rather complicated HDA being used in Maya and find almost every time I use it, but not every time, I get duplicated groups as what I created in Houdini - one group is the actual mesh and the other group is an nParticle. This doesn't happen every time I use the HDA in Maya but when it does, it creates a Nucleus in Maya and then doubles up the groups as mentioned above.

In the script editor I get the following error:
#
// Warning: Attempted to create 4550 polygons, but only 4546 polygons were created. //
// Warning: Attempted to create 18272 face-vertices, but only 18184 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. //
// Warning: Attempted to create 52 polygons, but only 36 polygons were created. //
// Warning: Attempted to create 208 face-vertices, but only 144 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. //
// Warning: Attempted to create 52 polygons, but only 36 polygons were created. //
// Warning: Attempted to create 208 face-vertices, but only 144 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. //

Which makes sense, though I can't figure out which primitives it is having an issue with, and it is further complicated by the fact it doesn't happen every time I use the asset in Maya. Also when this occurs, it creates an nParticle group for every primitive group I created in Houdini, not just the problematic group, so I can't figure out which mesh(es) the issue is coming from.

Has anyone else exhibited this? I also found sometimes what “looks” correct in Houdini, and by that I mean normal direction, where all normals are facing the same direction and no primitives are black, is flipped for some primitives once used in Maya. To make the normals face the correct direction in Maya, I end up using a reverse SOP on the primitive groups that are flipped in Maya and this then looks correct in Maya but flipped in Houdini.

Could this be causing an issue? Is there a clean way in Houdini to go to the end of the HDA and conform normal direction? I've been using a clean SOP and selecting “orient polygons” which appears to work for individual primitive groups but doesn't seem to work if I give it my final merged asset.

I'm using Houdini 13.0.621 and Maya 2015 SP5 on a 5K iMac running 10.10.1. Houdini Engine version 14.0.201.13. Not using H14 as it doesn't play well with my 5K iMac's graphics card but should be able to use H13 assets with the H14 engine for Maya all the same? The issue occurred while on the H13 engine for Maya as well but can revert if there are issues there.

UPDATE: The problem was a cookie sop that was generating bad geometry so i cleaned that up and the nParticles were no longer created.

For the normal problem, it might be because your geometry doesn't actually have normals defined? In Houdini, when geometries have no normals, the viewport will compute normals internally. Since these internal normals don't actually exist on the geometries, they don't get transferred into Maya. When this happens, Maya also computes its own normals, which probably doesn't match with what you saw on Houdini's viewport. So you probably want to try explicitly defining normals in your asset.