I'm bringing in a setup I've built in obj/sop land to attempt multi-shot work in Solaris.

There's lots of objects and lights instanced. I've got a frustrum cull HDA that works through the UV project method, so requires pointing to an actual camera objects. This works great in the old world.

In the new world - I want to discard any references to the original scene so I can read in USD cameras and do the cull sops in the instancer LOP. But how do I create a camera object from the camera primitive?

Am I going about this wrong? Suggestions?

In the mean time I'm just ensuring there's the original camera as an object in the hip file I can point to.

Hi Rangi!

Have you seen the %bound autocollection? https://www.sidefx.com/docs/houdini/solaris/pattern.html [www.sidefx.com]

I don't think there is a convenient node built on top of it yet, but it's not too hard to do.

Hey Jason!

Yeah, thanks for pointing that out. Looks like it should do the trick. Just doesn't work for me. I'm putting it into a prune lop. Testing with a simple bbox it's pruning the instances fine.

If I use it doesn't work. And using doesn't work either.

So not sure if bug or I'm just doing it wrong because LOPs are new to me.

Submitting a bug because if I point it to a camera that doesn't exist I get a seg fault.

h19.0.491

rangi
Yeah, thanks for pointing that out. Looks like it should do the trick. Just doesn't work for me. I'm putting it into a prune lop. Testing with a simple bbox it's pruning the instances fine.

It's not a bug, collections cannot target instances. The bound collection can only intersect with the bounding box containing all of the instances.

Here's a quick hip file showing how you can delete point instances by camera frustrum.

Dive inside the modify point instances LOP for details on how you can bring in the USD camera and reference it in a wrangle to delete unwanted instances.

Or simply do the same thing upfront in the instancer LOP before even creating the instances.

To answer your initial question, to create a camera from a USD camera prim, you need to use the LOP Import Camera node in an object context - from there you can reference it as you would any normal camera.

jsmack
It's not a bug, collections cannot target instances. The bound collection can only intersect with the bounding box containing all of the instances.

OK - cool. I've got lots to learn about USD / Solaris still! Thanks.

npetit
Here's a quick hip file showing how you can delete point instances by camera frustrum.

Sweet as... so the Lop Import Camera is exactly what I was looking for. Going to adopt your toNDC wrangle over my outdate UV texture sop too.


My problem is solved. Just left academically wondering now how one would go about this if you'd already made the instances and you wanted to prune them?

rangi
Just left academically wondering now how one would go about this if you'd already made the instances and you wanted to prune them?

Ah - I see you actually answered that in the hip file. Delete points inside "Modify Point Instances" LOP... Great!

npetit
Here's a quick hip file showing how you can delete point instances by camera frustrum.

Thanks for this file, I've just been playing with it. I would avoid simply deleting the points if animating the camera over time. As it appears to be writing the full point instances arrays for every frame, and I've had issues with instances strangely interpolating over time..

Instead use a SOP_visibility to hide the culled points.

Usd then writes a tiny file, only containing an array for invisible ids.

npetit, thanks again for the setup.