Importing SOPs and OBJ Hierarchies into Houdini Solaris (LOPs)
24 Jul 26 (2mo ago)
Okay, I know Solaris (LOPs) has been out for a while now, but I still catch myself forgetting the exact steps when integrating it with traditional SOPs/OBJ setups.
Long story short: if you want to avoid all the extra setup, just go straight to the Stage Context (LOPs), drop down a SOP Create node, and do your usual SOP thing inside it. It behaves pretty much the same as creating geometry inside the old OBJ context.
However, if you're importing existing work from OBJ/SOPs into Solaris, here are the two main ways to do it—and a huge gotcha to keep in mind:
Option 1: SOP Import (Scene)
- Drops in everything from your scene (objects, cameras, lights, etc.).
- Very straightforward and quick, but can get messy fast if your scene is complex.
Option 2: SOP Import (Regular)
- Lets you target and import specific objects one by one by defining their paths.
- Keeps the LOP graph clean, but has one major gotcha.
The Parent Hierarchy Gotcha
If you import an object or camera that relies on parenting in the OBJ context, a regular SOP Import won't carry over those parent transforms.
For example, my usual workflow for animating cameras in the OBJ context is to parent the camera to a chain of Nulls so I can isolate axes and translations cleanly. If you bring that camera into Solaris with a single regular SOP Import, it ignores the parent Nulls' transforms, leaving your camera stuck in place or misaligned.
To keep parented rigs and camera hierarchies intact in Solaris, use SOP Import (Scene) or fetch the parent Nulls explicitly so USD can resolve the full transform hierarchy.
P.S. I'm probably going to force myself to use LOPs more often now. I'm running a perpetual Redshift license that isn't compatible with newer Houdini versions, so I gave Karma XPU another shot—and wow, it's nowhere near as slow as it used to be. Yooohooo!