D3D12 TextureArray2D mipmaps missing/broken

[TokisanGames]

Tested versions

Reproducible in 4.3, 4.4dev3

System information

Windows 11/64, RTX 3070, D3D12

Issue description

In the Direct3D12 renderer, TextureArray2Ds don't seem to generate mipmaps so breaks Terrain3D and all other projects using them.

This code shows the next two images:

void fragment() {
    NORMAL = mat3(VIEW_MATRIX) * normalize(v_normal);
    // broken
    ALBEDO = texture(_texture_array_albedo, vec3(UV, 0.)).rgb;
    // works
    //ALBEDO = texture(test_albedo, UV).rgb;
}

Forcing mip 0 with vec2(0) derivatives also works.

Downstream issue TokisanGames/Terrain3D#529

Minimal reproduction project (MRP)

• Create a new Godot project
• Download Terrain3D from the asset library
• Enable the plugin, open the demo, restart twice
• Change to D3D12

If you wish to edit the shader, enable Terrain3D / Material / Shader Override.

[ArseniyMirniy]

This is definitely the case where the project would be very helpful to reproduce it

[TokisanGames]

@ArseniyMirniy I added instructions that will take 2 minutes to create a test environment.