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[4.9] Skylight not affecting volumetric lit translucency

We recently updated our project from 4.8 to 4.9 without any problems, however, once opening a level, I noticed all particles and meshes using a directional or non-directional volumetric translucent shader were not receiving any lighting from our movable skylight (ie rendered black in shadows). I made a test scene with 4 shaders, each having 1 in base color and nothing different other than the lighting settings:

alt text

Curiously surface translucency works fine but the volumetric options do not. Additionally, post process ambient cubemap seems to affect translucent lighting as usual but is incompatible with my project for other reasons.

Product Version: UE 4.9
4.9skylight.jpg (90.5 kB)
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asked Sep 15 '15 at 07:44 PM in Bug Reports

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James Steininger
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avatar image Lovecraft_K ♦♦ STAFF Sep 15 '15 at 09:09 PM

Hi James -

I am attempting to replicate this issue and so far I have not had any luck. Here is the results that I am getting:


and without Skysphere:


Can you take a look at this sample project I have attached below and makie any adjustments to better match your project and see if you can replicate this issue?

Thank You

Eric Ketchum

Test-Project 4.9.1

test.jpg (63.7 kB)
test01.jpg (16.4 kB)
avatar image James Steininger Sep 20 '15 at 09:49 PM

I was not able to open your project file - could it be because my team is still on 4.9.0? We built the engine our self from the release branch on git but only have added PS4 support to it.

avatar image Lovecraft_K ♦♦ STAFF Sep 22 '15 at 02:51 PM

Can you try this project, it was made with a Github 4.9.0 release?

Thank You

Eric Ketchum

Test Project 4.9.0

avatar image James Steininger Sep 23 '15 at 01:29 AM

This project works, and looks identical to your image above. There must be something wrong with our project - maybe something in the .ini files? We migrated all the configuration files to the new engine so maybe something has changed. Have any idea on where to start looking?

avatar image James Steininger Sep 23 '15 at 01:47 AM

Confirmed - I removed the "defaultEngine.ini" from the configuration folder and the lighting on the translucency shaders is restored. I'll update this when I find which setting is causing this.

avatar image James Steininger Sep 23 '15 at 02:02 AM

Found it - "r.AllowStaticLighting=False". We don't have any lightmaps in our game but apparently having this disabled in 4.9 invalidates translucency lighting from a skylight - even a movable one. Hopefully this helps someone else!

avatar image James Steininger Sep 23 '15 at 01:59 PM

I ended up reverting back to "r.AllowStaticLighting=False" because it affects the way material AO is used with dynamic lights (if it is enabled, it does not affect them). Is there a way to keep the material AO and lit translucency from skylight?

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Hi James -

Thank you for your further investigation, this matches up with another issue that I reported recently as UE-21369, so I have expanded that report to include the information here and will let you know as we progress to a solution.

Eric Ketchum

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answered Sep 23 '15 at 01:58 PM

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Lovecraft_K ♦♦ STAFF
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