DirectionalLight( mobility : stationary ) occlusion bug?

hi epic!
This problem has occurred in the process of turning ue4.12.5 → ue4.13.1


  1. file → new level → default
  2. make bsp tunnel
  3. build light
  4. play( mobile preview )


  1. directional light : mobility->static

  1. directional light : mobility->stationary

  1. directional light : mobility->movable

Directional light (mobility: stationary) is the wrong.
How do i fix the Directional light for mobile( mobility:stationary ) ???

Hell kkskm,

Can you reproduce the issue without upgrading from 4.12.5 to 4.13.1, in a new blank project?

I have a few questions about your setup. You say create a new level with a BSP tunnel, but I would like some clarification it what you mean? Are you creating a hollow additive cylinder brush?

Also, I need to know the mobility of the skeletal mesh you are placing as that is a factor of the results. What is it you expect to see when using a Stationary Directional light?

There are a number of facets to Stationary lights that you need to take into account when building your lighting. Have a look at the documentation below for more information.

Let me know if you have additional questions.


This problem has occurred only mobile and mobile preview in ue4.13.1

  1. i make a test map using the startup package
  2. all default option
  3. It is placed sk_mannequin
  4. placed wall

play mobile preview

This problem has occurred only skeletal mesh
skeletalmesh is sparkles

Test done in the same conditions results in the ue4.12.5

The correct light.

Stationary Directional lights can be used to cast Whole-scene Dynamic Cascade Shadow Maps (CSM) shadows for just the dynamic objects in your scene. If you want shadows from Static Meshes placed in the environment to cast shadows on the character, you will need to change the Mobility settings on the Static Mesh from Static to Movable.

Stationary Directional Light Settings



One of the benefits to using CSM shadows is that they will blend correctly with precomputed shadows cast by the static objects in the scene. CSM shadows also do not exhibit the double shadowing you see with Modulated shadows and are faster when casting dynamic shadows for multiple objects.

We have two different dynamic shadowing techniques that are implemented for mobile, each with their own strengths and weaknesses. I would take a read over our documentation for each of these techniques to get see which one will work best for your own case.

[Lighting for Mobile Platforms][4]

[Cascaded Shadow Maps][5]

[Modulated Shadows][6]

Let me know if you have further questions.