I used a file COP to read in an image that I want to use as a texture with the PrincipledShader, but using the op: syntax to get the image data from COPs doesn't seem to work.

I pointed to the image file on disk first, and that worked ok, so I'm not sure if I'm doing something wrong with COPs, or is this just not supported at the moment (using Houdini GL delegate FYI).

No, using COPs as an image source is not supported in Solaris right now. You need to write the images out to files on disk. This is because there is no facility in USD that would allow us to create a plugin that would allow COPs to work with all render delegates. It didn't seem worth the development effort that would be required here to make these COP paths work for just Houdini GL and karma. It is something we would like to revisit at some point, but given its limited applicability it isn't very high on the priority list.

The viewport's underlying texture mechanism is pretty much the same between Objects and LOPs, so I've fixed HoudiniGL by avoiding the USD resolve that converts the op:/path/to/some/file to a (missing) temp file. The viewer code can then properly fetch the texture (18.5.234).

Thanks for the explanation @mtucker, and thanks for adding it to the next release @twod!

Hello, I'm not sure if I read it right, but when I use op: syntax in a material library in Solaris, it does work.

Is this a new feature? Or I misunderstood what you were talking about?

Where it falls short is with other render delegates, or when you use usdrender or husk to write in the background.

Solaris doesn't detect these op:referenced COP nodes and write them out to disk, then read them back in. It's useful for dialing textures in for Karma perhaps, but you'll want to write the textures out before rendering in the background/farm, and/or with other renderers.

goldleaf
Where it falls short is with other render delegates, or when you use usdrender or husk to write in the background.

Solaris doesn't detect these op:referenced COP nodes and write them out to disk, then read them back in. It's useful for dialing textures in for Karma perhaps, but you'll want to write the textures out before rendering in the background/farm, and/or with other renderers.

Oh ok, I got it. Thank you very much.

goldleaf
Where it falls short is with other render delegates, or when you use usdrender or husk to write in the background.

Uh, wait, but the only way to render LOP network with Karma to MPlay/Disk is with usdrender or husk, right? So it means this feature is basically useless? Because even if I can see the texture in viewport, there is no proper way to render it out as the production render?

raincole

goldleaf
Where it falls short is with other render delegates, or when you use usdrender or husk to write in the background.

Uh, wait, but the only way to render LOP network with Karma to MPlay/Disk is with usdrender or husk, right? So it means this feature is basically useless? Because even if I can see the texture in viewport, there is no proper way to render it out as the production render?

You could use a workflow where you iterate with "live" textures this way interactively, but switch to writing out the maps to disk when you want to offline-render it. On top of this, I'm wondering if Karma has the some performance issues when using non-mipmapped textures, etc.