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Backface not lit on a Static mobility mesh


I have a very simple setup with a weird result:

  1. A single Directional light with Static mobility, shining straight down, with Indirect Lighting Intensity set to 0 to keep only direct lighting in the scene.

  2. A Plane static mesh with Static mobility and a simple Two-Sided Material applied.

Problem - the backface doesn't receive any light when it should, please see the pics. I built lighting before taking screenshots. If I set the mesh to Stationary mobility then the backface gets lit correctly, but shouldn't that work with the Static mobility too? What's wrong?

alt text alt text

Product Version: UE 4.16
ueq1.png (522.0 kB)
ueq2.png (568.5 kB)
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asked Jun 16 '17 at 04:33 PM in Rendering

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21 1 2 6

avatar image Ninjin Jun 17 '17 at 10:32 AM

I'm also starting to think that it might be a bug. I even checked "Use Two Sided Lighting" under the Mesh Lighting settings and still don't get the right result.

avatar image SergoK Jun 17 '17 at 12:59 PM

Hi again,

I'm attaching a minimal scene for testing - put to the Content folder, open the TestLighting map and set Lighting Quality to Production. The scene contains only the following:

  1. Two directional light sources shining straight up and straight down. Their Indirect Lighting Intensity is set to 0.

  2. Two Plane static meshes with a simple Two-Sided material applied.

I varied their mobilities and reconfirm that a Static Mobility light source does not light the backface of a Static Mobility mesh. So question #1: is this a bug?

I also found that a mesh set to Stationary mobility receives light from Static light sources properly on both faces, but if both meshes are set to Stationary then none receives lighting on any face. Question #2: what does Stationary mobility do for the Meshes? The documentation reads "Static Mesh Actors cannot have a Mobility of Stationary" which is obviously outdated.


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