Shaders: light-related built-in uniforms don't work correctly in custom shaders

[Indibulous]

Description

as mentioned in https://github.com/YoYoGames/GameMaker-Bugs/issues/6425 a number of uniforms listed on the Shader Constants manual page currently don't appear to work when accessed inside a custom shader. The gm_Lights_Direction, gm_Lights_PosRange, gm_Lights_Colour, and gm_AmbientColour uniforms, aside from having incorrect syntax highlighting as indicated in that issue, also seem to have some incorrect functionality:

• gm_Lights_Direction[] - Each vec4's w value seems to be always be 1, regardless of if the light has been enabled or disabled, despite the manual saying it should be 1 when the light is enabled, and 0 when disabled.

  • gm_Lights_PosRange[] - Each vec4's w value seems to always contain the light's range, regardless of if the light is enabled or disabled, despite the manual saying it should be 0 when disabled.

  • gm_Lights_Colour[] - Doesn't seem to work at all, with every vec4 in the array having a value of (0, 0, 0, 0) regardless of what colours the lights have been set to.

  • gm_AmbientColour - Works correctly, however, the alpha value will always be 0 unless draw_light_define_ambient() is provided with a colour in $AABBGGRR format, despite the built-in lighting system not using alpha values for ambient light. Unsure whether this is unintended or undocumented behaviour.

Here's an in-development version of the xUnit test framework which includes tests for these uniforms in the BasicShaderTestSuite: xUnit Shader Tests.zip

Expected Change

• The .w values of vec4s in the gm_Lights_Direction[] uniform should be 1 when the corresponding light is enabled, and 0 when disabled.
• The .w values of vec4s in the gm_Lights_PosRange[] uniform should be 0 when disabled.
• The gm_Lights_Colour[] uniform should contain the colours of all defined lights.
• And for gm_AmbientColour, it would be more intuative for the alpha value to be 1 when draw_light_define_ambient() is provided with a colour in $BBGGRR format, or at least the manual should document the behaviour of the alpha being 0 unless with $BBGGRR values.

Steps To Reproduce

1. Start GameMaker
2. Run the included version of xUnit: xUnit Shader Tests.zip
3. Check the Output after running to see the tests for gm_lights_direction, gm_pos_range, and gm_lights_colour failing
4. Open Users(user)\AppData\Local\GameMakerStudio2\GMS2TEMP\xUnit_(numbers)\ShaderTests for the visual test outputs
5. Open the LightsDirection, LightsPosRange and LightsColour folders in that directory and observe the difference between the expected and resultant values for the tests to see the issues. (note that there is an additional bug causing LightsDirection to fail, mentioned in #6507, causing the direction of the light to be inverted)

How reliably can you recreate this issue using your steps above?

Always

Which version of GameMaker are you reporting this issue for?

2024.6.0 (Monthly), 2024.600 (Betas)

Which platform(s) are you seeing the problem on?

Windows

Contact Us Package Attached?

• [X] I have attached my Contact Us Package

Sample Project Added?

• [X] I have included a small sample project

[Indibulous]

Just thought i should add, I initially only tested this in the GLSL/GLSLES shader language, which produces the behaviour described, but after testing in HLSL, found that the mentioned uniforms will just throw an error upon using shader_set() with the shader containing them:

I have created a new issue for this: https://github.com/YoYoGames/GameMaker-Bugs/issues/6840