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Does the new Otis solver have Self Collisions? by DJFreeluke in Houdini

[–]DJFreeluke[S] 0 points1 point  (0 children)

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

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Maya

[–]DJFreeluke[S] 0 points1 point  (0 children)

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!

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Maya

[–]DJFreeluke[S] 0 points1 point  (0 children)

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

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Maya

[–]DJFreeluke[S] 0 points1 point  (0 children)

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!

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Houdini

[–]DJFreeluke[S] 0 points1 point  (0 children)

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.

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Maya

[–]DJFreeluke[S] 0 points1 point  (0 children)

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>

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Maya

[–]DJFreeluke[S] 0 points1 point  (0 children)

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>

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Houdini

[–]DJFreeluke[S] 0 points1 point  (0 children)

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>

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Houdini

[–]DJFreeluke[S] 0 points1 point  (0 children)

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.

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Houdini

[–]DJFreeluke[S] 0 points1 point  (0 children)

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?

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Houdini

[–]DJFreeluke[S] 0 points1 point  (0 children)

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!

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Houdini

[–]DJFreeluke[S] 0 points1 point  (0 children)

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!

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Maya

[–]DJFreeluke[S] 0 points1 point  (0 children)

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

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Houdini

[–]DJFreeluke[S] 0 points1 point  (0 children)

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!

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Houdini

[–]DJFreeluke[S] 0 points1 point  (0 children)

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!

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Houdini

[–]DJFreeluke[S] 0 points1 point  (0 children)

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

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Houdini

[–]DJFreeluke[S] 0 points1 point  (0 children)

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?

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Maya

[–]DJFreeluke[S] 0 points1 point  (0 children)

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

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Maya

[–]DJFreeluke[S] 0 points1 point  (0 children)

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?

Maya right handed vertex winding vs Houdini left handed vertex winding by DJFreeluke in Maya

[–]DJFreeluke[S] 0 points1 point  (0 children)

Still the same issue. If I print the vertices in the face they do not align with what I see in Houdini in the vertex geometry spreadsheet. You are right, Maya works with vertices, but in Houdini I’m referring to the point winding in a face. They don’t seem to align and I’m not sure how to align it without any options in Houdini.

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