We are working on importing a large star catalog into our Houdini/Karma fisheye render pipeline.
Render times can be long, especially if we use sprites for star glow with partial transparency.
Is there a way to disable occlusion calculations in Karma?
We want to be able to accumulate samples and ignore alpha.

Stars are very far away (light years). So we can treat them as dimensionless points. Their light and color just accumulate/stack up. There is no occlusion.

Is there a way to mimic this behavior in Karma?
If not, could I submit this as an RFE?

Thanks

This might sound strange, but what if you add a single point light to your scene and set its intensity and exposure to 0 (this avoids auto-headlight creation). This will produce a black, shadowless scene. From there, assign your diffuse texture to the emission color instead of the base color. It's just stars, so the entire scene would be lit by emission.

my apologies. I didn't articulate our challenge with clarity.
It's a 3D star catalog. We need to fly through it.
We are rendering fisheye on 180 degree hemisphere for planetarium dome.
For dim stars we render points, with a Material X emission color, with Emission illuminates other objects disabled.
For bright stars we do need to render sprites with transparency.
The ability to disable occlusion, and instead accumulate Material X emission color per-pixel is what we would like to be able to do.
Thanks

jlapre
my apologies. I didn't articulate our challenge with clarity.
It's a 3D star catalog. We need to fly through it.
We are rendering fisheye on 180 degree hemisphere for planetarium dome.
For dim stars we render points, with a Material X emission color, with Emission illuminates other objects disabled.
For bright stars we do need to render sprites with transparency.
The ability to disable occlusion, and instead accumulate Material X emission color per-pixel is what we would like to be able to do.
Thanks

If you have access to 19.5, a new materialX shader has been added called 'MtlX surface unlit' that has transmission color, which allows colors behind the surface to pass through. Beware that this is technically refract rays so set limits accordingly.