Solved Subd problem in viewport in bl 3.1

Support Modeling
1

i did a model in 2.79

remove the middle verts with merge
and works fine

but when i import it in bl 3.1

i get some distortion on the middle edge loop ?

zw1
zw1718×525 20 KB

ca someone explain how to get rid of this distortion in bl 3.1

thanks
happy bl

2

Are you using custom split normals by chance?

A friend of mine had a similar issue looking problem a while back when he attempted to migrate some mesh objects from Blender 2.79 to Blender 2.8+.

His solution was to apply all custom split normals before attempting to migrate from 2.79 version to 2.8+.

https://docs.blender.org/manual/en/2.79/modeling/meshes/editing/normals.html#custom-split-normals

3

i check and for whatever reason in bl 3.1 i had to re calculate the normals

this was not needed in 2.79

so not certain why i had to redo it in 3.1

thanks
happy bl