USD authored in houdini solaris not working properly in painter

[Patrick Traile]

When I import any of my usd assets that were authored in houdini, they come in all messed up like the normals are going crazy or something. Painting on the mesh doesn't really work either. Any HELP here would be much appreciated. I can send one of my usd assets if necessary for anyone willing to help to test it for yourself. Thanks in advance.

[Patrick Traile]

Hello again, I've found the issue here, it's because the models had no subdivision scheme attribute. In Solaris, you can either author one yourself or turn on 'Treat Polygons as Subdivision Surfaces' for the SOP Import or SOP Create LOPS. To see the issues I was having, just remove any subdivision schemas and import them into painter and your mesh will look weird.

[Patrick Traile]

OK, back again with this, I'm having new issues due to the subdiv schema. Why can't painter work well with meshes that don't have subdiv schema? or even meshes with subdiv schema set to none. It loads the mesh, but it's all messed with parts of it invisible and the painting is totally whack. When you have a subdiv schema it screws up the UVs because of the subdivision and can cause all sorts of weird ass distortions (see image) that requires additional edge loops or maybe some sort of creasing. I just want my original usd mesh (no subdivision from USD) file inside of painter! How can I achieve this?

[Cyril Dellenbach]

Hi @Patrick Traile and hi @Clayton294737547rh9,

Thanks for your messages and sorry for the delay in response.

The .USD's implementation inside Substance 3D Painter being fairly new, it is the first time I personally heard about this issue. Would you mind sharing your file so we may dig deeper?

Keep me updated.

[Clayton294737547rh9]

Please find the .7z attachement here - https://www.dropbox.com/s/wih64ceiprrcb81/adobe_demo.7z?dl=0 =

Had to use dropbox to transfser as .zip, .7z, .usd* files do not seem to be uploadable to this forum.

Inside the 7z you'll find a houdini base scene which generated the 4 usd files. There are 2 primary files (left and right handed USD) in binary and ascii flavor.

Try bringing them into Substance Painter and you'll see that the left-handed ones have flipped normals.

Here's the issue,  the USD file describes if the vertex winding order is left handed or right handed. Even though painter may only support right-handed, it would be my assumption (wrong possibly) that it would be possible to properly interpret left-handed winding order on import, 

Let me know what you find out. Thanks.

[Clayton294737547rh9]

I am also having issues with Substance Painter interpreting USD files generated out of Solaris, specifically as it relates to flipped normals...

Here's what I think I know -

Houdini is a right-handed coordinate system and obsererves right-handed vertex ordering.

USD is a right-handed coordinate system and obsererves right-handed vertex ordering.

Substance Painter  is a right-handed coordinate system and obsererves right-handed vertex ordering.

However, it seems as if either Houdini is exporting USDs as left-handed OR Substance Painter is incorrectly interpreting Houdini generated USD's as left handed.

I found an immediate fix for this is to enable 'Reverse Polygon Vertex Ordering' when exporting USDs from Solaris - usdexport SOP docs (under 'Reverse Polygon Vertex Ordering').f

However, this is unacceptable for anything other than a one-off.

Can we get someone at Adobe to double check this perhaps? See attached Solaris generated USD. Why are the normals flipping between two seemingly right-handed coordinate system based software and USD which should also be right-handed by default?

Please note, the attached USD files SHOULD be named correctly (left handed = reversed vertex order / right handed = Houdini Solaris default). 

Or at least I would attach the USD files if your forum would let me attach the USD files. Adobe - might want to add that.

[Clayton294737547rh9]

I mispoke. Houdini is a right-handed coordinate system with left-handed vertex ordering!

Substance Painter must be a right-handed coordinate system with right-handed vertex ordering then. Bah - I just want to import some geo! 🙂 

Wonder if there is a way for Adobe to interpret left-handed vertex ordering in it's right-handed vertex ordering system.