Developer Notes

By Design: Normals (and positions) are always affected by blend shapes/morph targets regardless of the recompute tangent mode. 4.13 is wrong.

Description

In 4.13 if you imported a skeletal mesh with a blendshape and run the blend shape. The normals are not recalculated.

To Recalculate the normals during runtime you need to edit the Console Variables.ini and add

r.SkinCache.CompileShaders=1
r.SkinCache.Mode=1
r.SkinCache.RecomputeTangents=1

And then on the skeletal mesh you have to enable Recompute Tangent.

In 4.14 release.
Without enabling anything, Skin cache or the recompute tangent (Skin cache needs to be on for this to work) tangents are recomputed on blendshapes anyway.

Steps to Reproduce
  1. Download the release build and open the editor
  2. Create a new blank project
  3. Import the attached file with Import Morph Targets enabled
  4. Add the animation Smooth_sine_Anim to the gameworld
  5. Change the view mode to World Normal
  6. Hit simulate
    Result
    As the animation plays the normals are recalculated without SkinCache turned on Or Recompute tangent enabled on the skeletal mesh

Have Comments or More Details?

There's no existing public thread on this issue, so head over toAnswerHub just mention UE-38360 in the post.

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By Design
ComponentRendering
Affects Versions4.14
Target Fix4.14
CreatedNov 8, 2016
ResolvedNov 8, 2016
UpdatedApr 27, 2018