Shadow line when using OmniLight at a specific angle

[Alastor01]

Godot version: Godot 3.1 Beta 3

OS/device including version:

• Windows 10 64-bit
• GPU: Nvidia GTX 1050 Ti 4Gb

Issue description:

• When setting both Camera and OmniLight at the same point at the same angle facing X axis, a weird shadow line appears on the surface you face at runtime (Picture attached to demonstrate the issue)

Steps to reproduce:

• Create new project, use default settings
• Import wall / ceiling tile with basic color or texture, convert to Meshlib and use as your tile
• Add Spatial, add GridMap as a child, set it up to use your tile
• Add Camera, OmniLight and WorldEnvironment; all as children of Spatial
• OmniLight settings: Shadows enabled, Reverse Culling enabled, Bios 0, Contact 0 (otherwise shadows look horrible)
• Make a basic plane out of ceiling / floor tiles
• Make sure both Camera (rotation: y: -90) and OmniLight face in the same direction, X arrow
• Make sure both Camera and OmniLight are in the same position relative X and Z axises (camera can be in front of light as well)
• Run your the scene from this camera
• Observe the line right in front of you on the wall and / or ceiling, roughly in the middle

Extra steps:

• Move the camera towards the line (parallel to it) - it does not disappear
• Move the camera away from the line - it disappears if you are further than light origin / pivot point
• Rotate Camera - line disappears
• Rotate OmniLight - line moves with it

Minimal reproduction project:

• Included, please run Test.tscn Shadow_Bug.zip

[clayjohn]

I can confirm using intel integrated graphics.

[eon-s]

Same for amdgpu on linux, it seems like a limitation of the omnilight, put it a bit far from the surface and the line disappears.

I remember seeing other artifacts when the light on cube mode is too close to objects.

[Alastor01]

@eon-s Ye, it would be problematic for FPS games using such light sources, as the artifact depends on exact location and rotation of camera in relation to OmniLight

[dioptryk]

I've had this problem recently on GTX 970, Godot 3.1.1-windows. I'm writing a 3d dungeon crawler game, shown from first person perspective; after adding a Camera (player) with a light (torch), I've had horrible striping artifacts, no matter the bias/shadow quality or other config options (you name it). The thing is, the OmniLight was a a child of Camera and was set at (0, 0, 0) in relation to parent. The moment I moved the light a bit (about 0.2 in all directions, simulating handling the torch in right hand, and my geometry scale is pretty small, person size < 1.0), voila - all the shadows started working instantly with no artifacts whatsoever (even the performance got better). I think this case should be documented (Camera-Light position relation).

[KoBeWi]

Still valid in 3.2.4 beta3 The project is broken on master (mesh is invisible).

[clayjohn]

Fixed in 4.0. The problem here comes from using dual paraboloid shadow mapping. Godot 4 now uses cubemap shadows by default and avoids this issue