# Performance Hit Fixing Unbuilt Light Interactions in VR Level

**URL:** <https://forums.unrealengine.com/t/performance-hit-fixing-unbuilt-light-interactions-in-vr-level/2657461>\
**Category:** XR Development\
**Tags:** static-lights, unreal-engine, skeletalmesh, Rendering, question\
**Created:** [September 17, 2025, 8:13am UTC](https://forums.unrealengine.com/t/performance-hit-fixing-unbuilt-light-interactions-in-vr-level/2657461 "2025-09-17T08:13:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![XxpiingyxX](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@XxpiingyxX](https://forums.unrealengine.com/u/XxpiingyxX)\
**Post date:** [September 17, 2025, 8:13am UTC](https://forums.unrealengine.com/t/performance-hit-fixing-unbuilt-light-interactions-in-vr-level/2657461/1 "2025-09-17T08:13:08Z")

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Hello!

> **Project notes**
>
> **This project is for VR PC.**
> 
> ALL lights are set to static and built with “Build lighting only”.

> **TLDR:**
> 
> In a VR PC project with static lighting, unbuilt light warnings remained due to skeletal meshes marked _Movable_ under _Static_ parents in blueprints. Fixing it by making parents _Movable_ removed the warning but hurt performance (12ms → 19ms). Rebuilding the animation isn’t an option.
> 
> **Questions:**
> 
> - How can this be optimized?
> 
> - Can a skeletal mesh remain in a static parent without causing lighting issues?
> 
> - If left as-is (with the unbuilt light bug), will it cause visual problems in a shipping build?

I had a light bug in my VR project; whenever I would build the light and then reopen the level I did the build in, I would still receive the Unbuilt light warning.

To find out which lights where unbuilt, I used the command **DumpUnbuiltLightInteractions.** This in its turn did show a few unbuilt light but also a few _Primitives with unbuilt interactions._

After some testing I found out that the unbuilt interactions was blueprints with a skeletal mesh component set to Movable but a “parent” to the attached SK was set to static. Setting the parent to movable solved the problem with all unbuilt light warnings in the level.

**However,** this resulted in the level going from 12ms to 19ms, with one of the higher thieves being the shadows (of course).

I guess one workaround would be to recreate the animation (its an electric door with hydraulics that have an open/close animation) with constraints in blueprints, but that is currently not an option.

So **my questions are** , how can I optimize this? Is there a way to have the SK in a static parent in the blueprint? If I keep the bug, will it cause problems in a shipping build? Why does this lightbug happen?

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**Author:** ![XxpiingyxX](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@XxpiingyxX](https://forums.unrealengine.com/u/XxpiingyxX)\
**Post date:** [September 17, 2025, 2:08pm UTC](https://forums.unrealengine.com/t/performance-hit-fixing-unbuilt-light-interactions-in-vr-level/2657461/2 "2025-09-17T14:08:29Z")

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Another thing I don’t understand is that when a SM is set to movable in the BP and bake light, the texture renders wrong like if the UV is incorrect. But if I set it to Static, the Texture is correct but I will receive multiple warnings because it is a moving object.