MultiMeshInstance3D Fade Mode Culling doesn't respect AABB

[TokisanGames]

Tested versions

4.3-stable, 4.4-beta3

System information

Godot v4.3.stable - Windows 10.0.22631 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 3070 Laptop GPU (NVIDIA; 32.0.15.6614) - 12th Gen Intel(R) Core(TM) i9-12900H (20 Threads)

Issue description

Normally, both MeshInstance3Ds and MMIs cull based on comparing the AABB of the visible meshes with the visibility_ranges.

This means, even if the MMI instance transforms are far from the location of the MMI node, they are still culled based upon distance to the center of the AABBs encompassing the instances. The MMI location is ignored.

However, if visibility_range_fade_mode = self, this is not true. Shadows correctly cull based on the AABB. The visual mesh is incorrectly culled by something else, so the shadows show but the mesh does not.

This is preventing us from providing fading between instance LODs in Terrain3D.

MMI location in the center of the instances AABB

MMI location far from the instances AABB

Steps to reproduce

Open the MRP. Look at TestArea3. Move the camera towards the center of the grey areas. Read the README node for more info.

Minimal reproduction project (MRP)

test-mmi-margin.zip

[clayjohn]

We probably need to copy the same logic used for LODs into the code for fading. See here for reference: #92290