Houdini to V-Ray primitive userdata

[AlexOddbratt]

I'm exporting geometry from Houdini that has a primitive userdata attribute that I would like to access in V-Ray.
I can't seem to find any documentation on accessing per primitive or per point attributes from an alembic file with the vrayUserInteger nodes
as all documentation seem to indicate that it only handles per object attributes and not per component.

What is the "proper" workflow for naming, exporting and accessing/rendering these types of attributes between Houdini and Maya/V-Ray?

[yolov]

If the data is written in a specific channel, then pasting the name of the channel into userInteger or userColor should work with VRay.
Could you share an example alembic so we can run some tests? Also, any details on what the exact desired result is would be very helpful.

[AlexOddbratt]

I've attached our test alembic. There's a primitive integer variable named twigshading and we also tried with vrayUserInteger_twigshading.
We want to access this variable in order to do shader/texture variations.

[yolov]

Unfortunately this doesn't seem to work very well. I'll let the devs know and see if they can look into this. But in the meantime, could you export the same file, only the change the name of the variable so it doesn't contain "vrayUserInteger"?

[AlexOddbratt]

The file already contains one variable called "vrayUserInteger_twigshading" as well as one just called "twigshading".

[yolov]

Ah, OK. I saw that there were two channels, but didn't know that they were the same. Thanks for the info.

[yolov]

OK, I ran some more tests - it seems that VRay can't read the color sets. I've logged this as a bug. In the meantime, however, I'd like to ask for some more into: the file seems to contain only one color set. Is that correct? Or is it supposed to contain two?

[AlexOddbratt]

We jumped back and forth between testing the two attributes, but in the end we only need one attribute, "twigshading".
Might be that the alembic I sent you have both attributes as I wasn't sure how it should be named in order for V-Ray to pick it up so I tested both.