Vulkan Mobile: BaseMaterial3D Rim effect creates a dark dot on the mesh while moving the camera

[JeanKouss]

Godot version

v4.0.beta8.official [45cac42]

System information

Windows10

Issue description

First, The issue concerns only mobile rendering mode.

When a mesh have a 3DStandardMaterial that applies a rim effect on it, a dark circle appear on the surface of the mesh when the camera is moving.

The circle seems appearing on the mesh at the intersection of the word boundary and one of the word axis.

Steps to reproduce

1. Create a scene
2. Add a MeshInstance3D and choose a mesh shape
3. Add a 3DStandardMaterial to the mesh and add a rim effect
4. Move the camera move around the object

Minimal reproduction project

N/A

[clayjohn]

Looks like an NaN in the specular contribution. If I remember correctly rim lighting is added to the specular so that makes sense. What is odd though is that the same code runs in the mobile and forward_plus renderers so you should be seeing the issue in both.