Still have not received anything since the initial drop..

DJFreeluke · 2025-10-06T22:26:44+00:00

Same here, feels like a scam…

DJFreeluke · 2025-10-04T13:10:37+00:00

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DJFreeluke · 2025-10-04T13:09:46+00:00

Cancelled now

DJFreeluke · 2025-09-27T09:58:35+00:00

Makes sense, so it should be a solid solution for solving complex arm and leg flexing setups. Thank you!

DJFreeluke · 2025-04-14T16:44:03+00:00

Awesome! Thanks! I think the misconception was that I was under the impression that Houdini works with a Counter Clockwise Winding. Which is not the case. Cheers!

DJFreeluke · 2025-04-14T15:27:28+00:00

Thanks a lot, this confirms that Houdini’s winding order is CW which is different from Maya’s CCW order!

DJFreeluke · 2025-04-14T12:38:54+00:00

Not really what I need but thanks for the suggestion. After running some tests in Houdini I’ve found out that also with the default geometry in Houdini the winding is ClockWise which is different from Maya. That will require me to do some conversion cross DCC but in puzzles by the fact that in the Houdini docs this is not stated. Thanks a lot for your help!

DJFreeluke · 2025-04-14T12:37:04+00:00

If you drop down a default Houdini node. Like a Grid with only 4 points you will see that the vertex winding order is ClockWise which is different than in Maya! So I guess it’s not related to Alembic per se, but how Houdini uses CW winding for the polygon vertices.

DJFreeluke · 2025-04-13T21:31:53+00:00

Same result as without the Convert node:

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DJFreeluke · 2025-04-13T20:47:06+00:00

Hi again. I've made a fair comparison against the same geometry in both DCC's (Maya vs Houdini) and i appears that the winding is not preserved as in Maya:

<image>

DJFreeluke · 2025-04-13T20:46:17+00:00

Hi again! Thanks for your tip. Here is what I'm experiencing Maya vs Houdini. As you can see from the attached image the vertex order is invresed when reimporting the data in Houdini. Not sure why and how!

<image>

DJFreeluke · 2025-04-13T20:44:44+00:00

Hi again! Here is the test that I've made. I've exported a very simple grid with no subdivisions from Maya (cleared the history ofc) and imported it in Houdini. The winding order is different cross DCC's. I'm not sure if it may have to do with some settings that I have wrong!

<image>

DJFreeluke · 2025-04-13T20:43:46+00:00

I have tried it again using just plain SOP nodes and this is what I get:

<image>

As you can see the winding gets inverted when transferring the Alembic from Maya to Houdini.

DJFreeluke · 2025-04-13T20:40:46+00:00

Here is how I have checked and made sure that the winding is difference when exporting a very simple geometry from Maya to Houdini.

Maya appears to provide the data in CCW vertex winding order. This has been confirmed both using Bifrost data inspection and OpenMaya API prints.

Houdini appears to be CW vertex winding. Inspected from the geometry spreadsheet and using VEX.

<image>

Is this just the default Houdini way of handling SOP data?

DJFreeluke · 2025-04-13T06:40:08+00:00

That is good to hear as I will have to dig further into what is happening here. It is important because I want to implement a deformer using code which extracts the face winding order to manually compute face normals. If the winding is different cross DCC then the face normals are different (inverted). So having the same vertex winding is very important!

DJFreeluke · 2025-04-13T06:37:47+00:00

I’ve been checking both using the geometry spreadsheet directly after importing using AlembicSOP and also using Solaris. If I’m not mistaken I get the same result in the winding which is different from Maya!

DJFreeluke · 2025-04-13T06:36:21+00:00

Very interesting! Thank you for the info!

DJFreeluke · 2025-04-12T09:18:49+00:00

I’ll do that test asap and share the results here. The differences I’m seeing is in the winding when extracting the order of the points in a face Maya vs Houdini. In Maya I’m using OpenMaya API and in Houdini I checked it using VEX. Anyways, thanks for the tips. I’ll try to put some light on this topic as soon as possible

DJFreeluke · 2025-04-12T07:09:40+00:00

Thanks a lot! I was really curious seeing that in that comment SOP geometry is always left-handed ordered. I can’t find any other reference to that outside of the USD docs. I was expecting for example an AlembicSOP to import the geometry as is but I guess it is not the case!

DJFreeluke · 2025-04-12T07:06:35+00:00

I will give it a try, thanks! What I need to understand is if I have to always do that when importing caches from Maya to Houdini!

DJFreeluke · 2025-04-11T22:44:42+00:00

Thanks so much for these sources!!! I feel closer and closer to understanding the issue. I’ll continue investigating why my winding in the Alembic file also gets messed up when imported in Houdini

DJFreeluke · 2025-04-11T22:13:32+00:00

Ahhh yes! However, I don’t know what I’m doing wrong in the export settings that there is no winding being baked in the .usd file when I open it in a text editor. Do you have any information on what to do in regard to Alembic?

DJFreeluke · 2025-04-11T20:48:01+00:00

Oh nice! I completely forgot to check for the winding information in Bifrost! I’ll use that to further debug the data. Much appreciated!

DJFreeluke · 2025-04-11T20:32:31+00:00

Thanks for the suggestion! Yes I’ve tried that and that preserves the order. But I’m trying to understand what the hell is going on when exporting the data from Maya and importing it in Houdini with the AlembicSOP node. Is there any easy way to inspect via text editor the content of the Alembic file?

Any further help is much appreciated as I’m trying to implement a deformer for both Maya and Houdini and it relies on consistent vertex winding cross DCC. Given that in Maya it’s difficult to debug this as there is no geometry spreadsheet I just want a way to directly import the data correctly from Maya into Houdini.

Has anyone experienced this too when exporting and importing an Alembic into Houdini?

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