SDFGI Ignores Dynamic Lights at High/Low Y Positions

[myersguy]

Tested versions

Godot Dev 4.6
Godot 4.5
Godot 4.0

System information

Godot v4.6.dev1.mono - CachyOS Linux #1 SMP PREEMPT_DYNAMIC Fri, 03 Oct 2025 17:06:47 +0000 on Wayland - X11 display driver, Multi-window, 2 monitors - Vulkan (Forward+) - dedicated AMD Radeon RX 7800 XT (RADV NAVI32) - AMD Ryzen 5 5600 6-Core Processor (12 threads) - 31.24 GiB memory

Issue description

SDFGI seemingly begins to completely ignore dynamic lights as Y values increase or decrease. The environment/sky/ambient light will still be bounced around surfaces, but dynamic lights will not create any indirect lighting.

Basic room at position 0,0,0:

Basic room at position 0, 200, 0 (no other changes):

Steps to reproduce

• Create a small room with a high energy spotlight and a camera (character controller optional). Mine is a StaticBody3D with mesh and collision.
• Add a world environment, and enable the default SDFGI settings
• If the small room is at position 0,0,0, SDFGI should work correctly, and the dynamic spotlight will bounce and create indirect lighting
• If the room is moved to 0, 200, 0, SDFGI will completely ignore the spotlight. The same is true at 0, -200, 0

Minimal reproduction project (MRP)

test-sdfgi.zip

StaticBody3D is at 0,0,0. SDFGI will work. Setting the transform of the StaticBody3D to 0, 200, 0 should break SDFGI for the dynamic light.

[Calinou]

I can confirm this on 4.6.dev 60710df (Linux).

Godot v4.6.dev (60710df) - Fedora Linux 42 (KDE Plasma Desktop Edition) on X11 - X11 display driver, Multi-window, 1 monitor - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 5090 (nvidia; 580.95.05) - AMD Ryzen 9 9950X3D 16-Core Processor (32 threads) - 62.33 GiB memory

I've toggled SDFGI off and back on before each screenshot to make sure it's up-to-date.

0, 0, 0

Debug cascades	Debug probes

0, 200, 0

Debug cascades	Debug probes

Moving the StaticBody3D by ±200 units on other axes works. It's only broken on the Y axis (positive or negative). Moving the StaticBody3D by 200 units on the Y axis and another axis also looks broken.

[myersguy]

Enabling Y-Scale 100% seems to fix this. I'm not sure if this is necessarily the intended use case, however.

[zuedev]

In servers\rendering\renderer_rd\environment\gi.cpp:

SDFGI cascade positions are stored in Y-scaled grid space, where world positions have been transformed by multiplying Y by y_mult. When converting these positions back to world space for bounds checking, the inverse transform (* Vector3(1, 1.0 / y_mult, 1)) must be applied.

The cascade_aabb construction in pre_process_gi() is missing this inverse transform, causing it to compare bounds in Y-scaled grid space against light_aabb in world space. This results in incorrect culling of dynamic lights at high/low Y positions when using non-100% Y scale.

I have opened a PR to fix this.