[4.17.2] can't get emissive materials to contribute to LPV

Tzur_H

hey everyone.  I started a project using LPV on 4.15, everything worked perfectly fine.  I decided to update to the latest build 4.17.2 , and now my emissive materials are no longer contributing to LPV.

r.LightPropagationVolume=1 in my ConsoleVariables
force no precomputed lightmaps checked
have a directional light with an intensity of 0.1 (since I want to rely mostly on emissive surfaces to light my scene)
emissive (dynamic area light) option checked.  the shader is just a GIreplace node hooked to emissive color channel using an unlit shading model.

am I missing anything?

Tzur_H

I was able to fix the issue.
project settings > rendering > optimisations > Early Z-Pass was set to "opaque and masked meshes" upon changing to any of the other 3 options, LPV kicked in.

I'm now facing another issue.  occlusion culling on causing my emissive surfaces to turn off when not visible in camera frustum - and thus turning off my light sources :P  is there a way to specifically tell UE4 not to occlude certain actors?

Tzur_H

Well, I dunno what happened to LPV in 4.17 but I managed to get everything back on track.  I hope writing these updates here might help someone who's facing the same issues.

Apparently, if you want to have emissive surfaces contributing to LPV, they must be air-tight, or, use two-sided shading.  No idea why... a cube worked fine, a plane didn't - but a plane worked fine when I set the material to be two-sided.