Hi,

I'm starting to dig into Solaris and Karma and have a couple of questions regarding AOVs:

1. With "Split per LPE Tag" turned on, I'm getting an extra and unwanted "_emission" AOV even though I only have a Domelight tagged with "env". I tried setting the tag on the light and using a LPE Tag LOP.
2. Even after pruning lights (tried both Visibility and Active state) not needed for a render, LPE AOVs from the pruned lights are still generated. Is there a way to prevent that?

Using 20.0.688 and tested both Karma CPU and XPU. Windows 11.

"Split per LPE" will find all LPEs on lights on the input stage and create as many of the selected AOVs as there are unique LPE tag values, and, in some cases, adds extra Emission AOVs as a failsafe - to catch the light contribution from emissive geometry which isn't easily captured through LPE tags. (H20.5 adds support for emissive geometry with "Treat as Light" on and geometry LPE Tags for finer control).

These AOVs are defined as RenderVar primitives that are added to the Render Product's orderVars relationship.
Pruning lights after the Karma Render Settings LOP won't affect the previously generated render var prims.

If you want to remove unwanted AOVs, use an Edit Properties LOP, point it to the render product primitive (/Render/Products/renderproduct by default) press the "Edit Properties" button, select "orderedVars" in the left column, press the right arrow so its control parm and the orderedVars parm get added to the right column, and hit Apply.
From there you can edit the list of render vars. Make sure to keep the Beauty render var as the first in the list.

Hi Nick,

"Split per LPE" will find all LPEs on lights on the input stage and create as many of the selected AOVs as there are unique LPE tag values, and, in some cases, adds extra Emission AOVs as a failsafe - to catch the light contribution from emissive geometry which isn't easily captured through LPE tags. (H20.5 adds support for emissive geometry with "Treat as Light" on and geometry LPE Tags for finer control).

While I don't agree with the "extra Emission AOVs as a failsafe", I understand it helps other users coming from mantra or 3rd party renderers and dealing with emissive geometry.

These AOVs are defined as RenderVar primitives that are added to the Render Product's orderVars relationship.
Pruning lights after the Karma Render Settings LOP won't affect the previously generated render var prims.

If you want to remove unwanted AOVs, use an Edit Properties LOP, point it to the render product primitive (/Render/Products/renderproduct by default) press the "Edit Properties" button, select "orderedVars" in the left column, press the right arrow so its control parm and the orderedVars parm get added to the right column, and hit Apply.
From there you can edit the list of render vars. Make sure to keep the Beauty render var as the first in the list.

I was pruning lights before the Karma Render Settings LOP as shown in the attached hip file but think I'm beginning to understand render var prims and relationship per your explanation.

My main concern was "Where is this Emission AOV coming from?" and was checking through lots of settings to make sure it's not something I was doing.

I was testing with Karma XPU and each additional AOV adds to the amount of GPU memory being used so I was trying to only output what was needed.

After a few days of searching and watching some videos plus your post about AOV per file in this thread [www.sidefx.com], I was finally able to prune the unwanted Render Var prims.

I tried to follow your instructions above to set up the Edit Properties LOP but didn't get anywhere so if you can point me to a video or tutorial, that will be great.

Thank you.

The pruned lights before the Karma Render Settings LOP should definitely be ignored. In the next version of Houdini this is now the case - I'll look at backporting this.

Here's a gif showing how to edit the properties/aov list.