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michaelb-01

Alembic export to Maya error

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I'm exporting some simulated geometry to Maya from Houdini and I keep getting the following error:

 

UVs aren't per-vertex or per-polygon per-vertex, skipping

 

And it won't load any UVs... All of the geometry has UVs in houdini and there are no "null" uvs (one point has 0,0,0 but that is correct). I've deleted all groups except the inside and outside primitive groups of the fracture and all attributes except:

 

point: P

vertex: N, uv

 

Alembic format is HDF5. 

 

I don't know what else to try!

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Looks like you have 2 UV sets under 1 Geo Node. Maya no like. I know its painful but object merge out to a separate geo node. The other thing that can cause this, is if you have merged 2 sop objects and 1 has uv's and the other doesn't, and you export that.

 

Basically for every object under a Houdini Geo Node, if any of them have UV's, you need to make sure that ALL of the points/verts have uv's.

 

-Nathan

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Ah, how do I see my UV sets in houdini? I did make sure they all have correct UVs so I don't think its that..

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Generally if your looking at merged sops with different uv's in houdini and go to your UV view they will just display as overlapping, but if your sure everything has UV's I would just try separating what you have based on connectivity, or if you want to give it a test (maybe you missed a surface or two) remove the old uv attribute and throw down a new uvtexture or uvunwrap and just do an auto thing and see if that works. If its possible for you to post the file I can have a look, I've gone through the ringer on debugging alembic crap for maya. Maya's interpreter is very picky.

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Hi Nathan, 

 

Thanks for your help. There are lots of overlapping uvs because they are the interior of the bricks (uv'd in maya), but that shouldn't be a problem right? I just tried deleting my old UV vertex attribute and using a uvunwrap on everything but I still get the same error.. I can't really post the hip file since its for a current job, I could send you the alembic if that would help? How do you go about debugging an alembic file?

 

Cheers

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I also get this warning:

 

normal vector scope does not match size of data, skipping normals // 

 

The normals and uvs are my only vertex attributes and the are both giving me warnings...

Also when I import it into maya the geometry is hidden and without a shader, I don't know if this is important...?

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Hmm it seems to work if I promote my UVs and normals to point attributes rather than vertex attributes... Which is strange since Maya doesn't even use points so I thought want vertex attributes?... So at least it works but promoting my UVs from vertex to point really screws them up.. is there a good way to do this?

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I found this thread where the outcome is that a bug that produced the same result as mine was fixed for version 1.1. I just checked and i've got 1.0 so that could be the problem. Is there an easy way to update alembic it looks like I need to build it myself...

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I managed to fix it the problem. To fracture my geometry I was using a foreach node (to have fractures per brick) iterating over the "name" attribute, then I would scatter points based on colour and fracture. Since some of the bricks had no colour they would have no points, therefore not fracture and therefore not come out the other end, so i was using a switch node to check if there were any points produced by the scatter, if not, keep the original brick. And for some reason that was screwing something up - if anyone knows why i'd be interested to hear!

Anyway I changed it so that every brick has at least two points and I got rid of the switch and now it works. Thanks for your help Nathan

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Just saw your last posts, glad you got it to work! The Alembic would come into maya hidden if the geo nodes visibility/display is turned off, were you using the alembic rop in sops or in /out ?

 

When I export I try to create a separate geo node that i merge into and name the merge after the geo node, appending Shape to the end so that maya likes it.

 

Cheers

 

-N

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Hey Nathan, ah that makes sense. I was using an alembic rop. It was definitely my foreach sop that was screwing things up though, i'll try and figure out why at some point! Actually just thinking now, i'm pretty sure I was checking if the scatter sop produced more than 0 points but I think even if you have one point that will give you nothing from the voronoi fracture so maybe that was causing the problem..

 

Thats a good idea, i'll do that in the future so my geometry is cleaner/maya-friendly. Cheers!

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Hey Michael, just found this thread ; was looking for someone who had the same issue. 

 

This morning I found out a way that worked for me....so I was importing the .obj geo which already had UV's (per vertex) on it and I had to create UV's for the inside faces (after voronoi fracture). I was experiencing the same problem of maya complaining about UV's being per vertex even if they actually were inside houdini. I ended up using an assemble sop to pack the geometry before exporting to alembic. Even if houdini can't show the uv's in the packed state, when I imported the geo in Maya it had perfect uv's with no issue.

Hope this helps anyone that might experience the same problem ! :) 

Edited by radurock
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Thanks Radu, i'll have to try this out! Very interesting that it reduces the size so much! And you're still able to edit verts and UVs in Maya as you would normally?

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<edit> think I resolved this altering alembic output parameters.

__________________________________________________________________________

hi... I'm fairly new to Houdini and came across this thread whilst trying to resolve UVs disappearing/corrupting going through to alembic opened in Maya.

From above thread, I've tried

a) packing again... didn't work

b ) promoting UVs from vertex to point... this shows UVs but new edges between the moved shells... .. so doesn't work

Nathan, I don't follow what you mean about merging the objects again.. are you available to look at my file please?

UVs look fine in Houdini, I've unwrapped new inside groups after a boolean (subtract), but alembic into Maya won't work for this step.

Edited by karlp
Update based on resolving.

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Found this thread looking into a similar problem. In my case, it was due to a Fuse SOP. The solution was to just disable that.

UVs in Houdini were there, even after exporting to Alembic and bringing it in again.
Maya (2015) gave me the error message the OP had and no UVs on some objects.

 

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