Developer Notes

This issue has been closed as 'Won't Fix' due to an extended period of time without updates. If this issue is important to you please let us know by posting on the AnswerHub or UDN, and Epic will re-open the ticket for further review.


When comparing the World Normals of an Instanced Static Mesh being scaled non-uniformly to that of a regular Static Mesh, their normals do not match one another.

I have attempted to look over the documentation that would provide some more documentation on whether or not this is intentional or not, but the user who is reporting seems to think it is "a rather large functional hole in the engine."

"Maybe we could have a bool on the instanced mesh component that, if set, would ignore the scale while transforming the per-instance normals. That way, we would get both, the performance and the correct normals."

"What's happening is that instanced meshes do not compute their tangent basis vectors correctly if the instance is non-uniformly scaled."

Steps to Reproduce

1. Launch Uproject from attached zip folder.
2. Click on the Instanced_SM_BP already placed in the scene, and within the details panel set the scale of the X-value to a high number. (something like 100 works fine)
3. Observe the difference between the Static Mesh normals and the Instanced Static Mesh normals.

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Won't Fix
CreatedApr 2, 2015
ResolvedFeb 17, 2017
UpdatedApr 27, 2018