Vulkan: Moving a light in a VoxelGI is extremely slow if no mesh has a Global Illumination Mode set to Baked

[Calinou]

Godot version: Git 11cd8b8

OS/device including version: Fedora 31, NVIDIA 440.44, GeForce GTX 1080

Issue description: After baking a GIProbe in a simple scene with a few lights, moving an OmniLight inside will take several seconds just to update the editor viewport. Attempting to move a light without using snapping will likely freeze the editor for more than 10 seconds.

Moving the VoxelGI node itself can cause this slowdown if the VoxelGI node is moved in a way that puts some of the lights outside its bounding box (notice the update spinner in the top-right corner):

voxelgi-dynamic-moving-slow.mp4

Moving a MeshInstance3D node does not cause this slowdown.

Steps to reproduce: Edit the attached reproduction project and try to move an OmniLight.

Minimal reproduction project: test_giprobe_vulkan.zip
_{Old MRP from February 2020: test_giprobe_vulkan.zip}

[Ace-Dragon]

I think the issue really stems from the fact that even moving the view can be pretty glacial, and this is on a machine that has no problem rendering out multiple GI Probes at high resolutions in Godot 3.2 (GTX 1060 GPU).

The actual computing part (creating the data) does not take that long.

[Calinou]

I can still reproduce this on commit 2a9dd65. It occurs as soon as no mesh with its global illumination mode set to Baked is present within the VoxelGI's extents: test_voxelgi_dynamic_only.zip

Note that this issue is unrelated to #55359, as here, we're talking about sub-1 FPS performance.

[Zireael07]

I seem to have triggered it on alpha 1. Before that, voxelgi performed fairly well even on my integrated Kaby Lake GPU.

[Calinou]

I seem to have triggered it on alpha 1. Before that, voxelgi performed fairly well even on my integrated Kaby Lake GPU.

I didn't notice VoxelGI performance regressions on master lately, although my above comment still applies if you have no meshes with the Static bake mode within the VoxelGI's extents.

[Calinou]

I can't reproduce this on 4.2.dev 6758a7f (Linux, GeForce RTX 4090 with NVIDIA 535.98), but I can reproduce it on 4.1.1. This was likely fixed at some point recently.