I have a scene that contain a sphere emissive object in the blue transparent cube.

If I didn't Enable The `Treat As Light Source` in the Render Geometry Settings Node. The rendering result will be dark.

But When I Enabled this option. the LPE of `Direct Emission` and `Indirect Emission` will output black screen and no results.

And When I Disbaled this option, It's going to be correct.



Has anyone encountered this issue? Is it my inappropriate operation or is it a bug?

Any help would be greatly appreciated.

Aaron

Same issue for me I've submitted two RFE for many months and no solutions

Hi, if you enable "Treat as Light Source" the emissive material is treated as light and not emission, so it will only contribute to LPE AOVs that accumulate direct/indirect lighting (i.e. expressions that end with 'L' not 'O').

As for the render being darker without light source: It's because diffuse indirect ray hitting transmissive surface (which then hits emissive surface or anything for that matter) is a caustic path and true caustics is disabled by default. Fake caustic is automatically enabled on MaterialX-based transmissive materials, so the colour of shadow rays for the light source is adjusted and thus appears brighter. Otherwise you'd have to enable true caustics (via rendergeometrysettings LOP on the glass object, or globally).

dlee
Hi, if you enable "Treat as Light Source" the emissive material is treated as light and not emission, so it will only contribute to LPE AOVs that accumulate direct/indirect lighting (i.e. expressions that end with 'L' not 'O').

As for the render being darker without light source: It's because diffuse indirect ray hitting transmissive surface (which then hits emissive surface or anything for that matter) is a caustic path and true caustics is disabled by default. Fake caustic is automatically enabled on MaterialX-based transmissive materials, so the colour of shadow rays for the light source is adjusted and thus appears brighter. Otherwise you'd have to enable true caustics (via rendergeometrysettings LOP on the glass object, or globally).

I understand. I've always understood it wrong before. Thank you so much. I tried to add an LPE Tag to this object, then write a custom LPE, only retain this object as the influence of the light, and then get the final result. The LPE tag of this object is `pemiss` and the LPE Expression is `C.*<L.'pemiss'>`

AAaronLi

dlee
Hi, if you enable "Treat as Light Source" the emissive material is treated as light and not emission, so it will only contribute to LPE AOVs that accumulate direct/indirect lighting (i.e. expressions that end with 'L' not 'O').

As for the render being darker without light source: It's because diffuse indirect ray hitting transmissive surface (which then hits emissive surface or anything for that matter) is a caustic path and true caustics is disabled by default. Fake caustic is automatically enabled on MaterialX-based transmissive materials, so the colour of shadow rays for the light source is adjusted and thus appears brighter. Otherwise you'd have to enable true caustics (via rendergeometrysettings LOP on the glass object, or globally).

I understand. I've always understood it wrong before. Thank you so much. I tried to add an LPE Tag to this object, then write a custom LPE, only retain this object as the influence of the light, and then get the final result. The LPE tag of this object is `pemiss` and the LPE Expression is `C.*<L.'pemiss'>`

Can you provide you hip file please, I'd like to test too
Thanks

This one is a simple file with my settings inside.

AAaronLi
This one is a simple file with my settings inside.

thanks