Vulkan: Automatic mipmap LOD bias based on resolution scale is discarded when Texture Mipmap Bias is set

[Calinou]

• Related to Vulkan: Mipmap LOD bias settings behave incorrectly when there are multiple viewports rendering 3D #84083.

Godot version

4.1.2, 4.2.beta3

System information

Fedora 38, GeForce RTX 4090 (NVIDIA 535.113.01)

Issue description

The automatic mipmap LOD bias based on resolution scale is discarded when Texture Mipmap Bias is set.

The expectation is that the Texture Mipmap Bias property should be an offset of the automatically chosen value (also relevant if TAA/FXAA/FSR2 is enabled), rather than an override. This was my original intention when implementing that property.

simplescreenrecorder-2023-10-28_00.42.46.mp4

Steps to reproduce

This can be done either with project settings for the root Viewport, or with a Viewport node. The MRP uses a Viewport node.

• Decrease Scaling 3D Scale to a low value like 0.5.
• Set Texture Mipmap Bias to a small value away from 0 such as -0.01.
• Notice how the effective texture LOD bias suddenly changes, even though there should be no notceable difference.

Minimal reproduction project

test_mipmap_lod_bias_scaling_3d_scale.zip