Hi, can anyone get this to work with Material X? To be clear, I'm not referring to transparency/transmission.

I seem to only be able to get it to work by using a Principled Shader that can read the Alpha attribute, but if I plug a USD Primvar Reader into the opacity input, it does nothing. The same Primvar Reader outputs the attribute to other parameters, like colour.

Is this feature just not supported yet? Seems like it should be considering it's a pretty basic one, and Karma CPU is out of beta now.

This is working fine for me in houdini 19.0.444. Are you sure you're connecting the correct primvar to Opacity? If the attribute was 'Alpha' in SOPs, it will be renamed 'displayOpacity' on import to solaris, unless this option is disabled.

I rolled my own attribute called 'opacity', that I checked against the list in Solaris, and I also plugged that same attribute into colour, which worked.

I'll update to 444 and check again. Thanks for the info.

So I got this to work by using a Material X Combine 3 rather than plugging the Primvar Reader directly into the Opacity input.

I'm still on 19.0.383, and happy to see that this works with XPU too.

Edit: So it doesn't exactly work perfectly. I think I've narrowed it down:
Karma CPU - when using the Combine 3 will read the displayOpacity primvar and use that correctly, but cannot use a custom opacity primvar.

Karma XPU - surprisingly works correctly with both displayOpacity and also any custom opacity primvar.

As of 19.0.383, both CPU and XPU need the Combine 3 node before feeding the Opacity input.

I downloaded 19.0.444 and now the conversion from float to vector is done for you, no Combine 3 needed, and both CPU and XPU read custom primvars.