VAT Softbody Normal Issue (Used in UE5)

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Joined: 5月 2023
I’m facing the issue of VAT Softbody normals.

(1) What I want to do
Apply a rim light effect to a VAT character imported into UE using a fresnel node of a material.

(2) Problem
Fresnel is not calculated correctly because the VAT normals are not correct.

(3) What I’d like to know
How to bake the correct normal information into the VAT Rotation Texture or the alpha of Position Texture.

I created a VAT Softbody using SideFX Labs and imported it into UE, but I'm having a problem with the fresnel material.

The image is a comparison of VAT and SkeletalMesh.
The fresnel on the arm is not displayed correctly when the VAT character raises her hand.

I’ve tried with other models, but the same problem occurs in areas with large animated movements (mainly arms).
In the World Normal View, there does not seem to be any error in the normals, but I think the cause is the VAT normals (Rotation Texture) since the fresnel is not applied correctly

The same result is observed when the normals are stored in the alpha of the Position Texture.
I'm guessing that a vertex gimbal lock occurred during VAT generation, causing the normals to flip.

I have uploaded Houdini and UE scene files on GoogleDrive. []

I would really appreciate it if someone could share with me any possible solution to this problem.

<My Environment>
Houdini Version: 19.5.650
SideFX Labs VAT Version: 3.0
Unreal Engine Version: 5.0.3
OS Version: Windows 10 Pro 22H2
Graphics Card & Driver Version: NVIDIA RTX A4000, 516.94
Edited by May_Mori910 - 2023年7月13日 06:10:57

VAT_Normal_Issue.png (3.1 MB)
VAT_Normal_Issue.png_Material.png (681.4 KB)

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