Referencing a built-in matrix within the light() function of a spatial shader throws an error; falls back

[ardlak]

Godot version

4.0.2.stable.official

System information

Windows 10, NVIDIA GeForce RTX 2080 SUPER, Driver 516.94, Vulkan backend

Issue description

When referencing a built-in matrix (MODEL_MATRIX, VIEW_MATRIX...) within the light() function of a spatial shader, these errors are thrown per renderer:

Forward+:

-   servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.cpp:171 - Condition "!shader_singleton->shader.version_is_valid(version)" is true.

Mobile:

-   servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.cpp:182 - Condition "!shader_singleton->shader.version_is_valid(version)" is true.

Compatibility (MODEL_MATRIX is referenced):

-  drivers/gles3/shader_gles3.cpp:242 - SceneShaderGLES3: Fragment shader compilation failed:
-   0(521) : error C1503: undefined variable "model_matrix"
-   drivers/gles3/shader_gles3.cpp:342 - Method/function failed.

The shader displays a fallback instead of what's written. This can be avoided by defining a variable that is identical to the matrix and referencing that instead:

shader_type spatial;

varying mat4 mdlMtx;

void vertex() {
	mdlMtx = MODEL_MATRIX;
}

void light() {
	mdlMtx; // works
//	MODEL_MATRIX; // doesn't work
}

Steps to reproduce

In a spatial shader, reference any built-in matrix within the light function:

shader_type spatial;

void light() {
	DIFFUSE_LIGHT += ATTENUATION; // lighting that should be displayed
	MODEL_MATRIX; // breaks the shader, displays a fallback
}

Minimal reproduction project

issue_light_matrices.zip

[clayjohn]

Looks like the rest of the matrices need to be renamed in the light function. This comes from the uniform for the matrices using a different name from what the shader compiler maps onto.

For example, here is what is done in the GLES3 renderer's fragment function:

godot/drivers/gles3/shaders/scene.glsl

Lines 934 to 945 in 9f12e7b

	#ifdef USE_MULTIVIEW
	vec3 eye_offset = multiview_data.eye_offset[ViewIndex].xyz;
	vec3 view = -normalize(vertex_interp - eye_offset);
	mat4 projection_matrix = multiview_data.projection_matrix_view[ViewIndex];
	mat4 inv_projection_matrix = multiview_data.inv_projection_matrix_view[ViewIndex];
	#else
	vec3 eye_offset = vec3(0.0, 0.0, 0.0);
	vec3 view = -normalize(vertex_interp);
	mat4 projection_matrix = scene_data.projection_matrix;
	mat4 inv_projection_matrix = scene_data.inv_projection_matrix;
	#endif
	highp mat4 model_matrix = world_transform;

The shader compiler turns MODEL_MATRIX into model_matrix, but the uniform is called world_transform so it needs to be remapped.

[mohsenph69]

I Think get some related Issue

When I use this to calculate light direction in world space;
vec3 light_dir = mat3(INV_VIEW_MATRIX) * LIGHT;

In editor it will give me no error but I will give me a huge error in console

   at: _compile_variant (servers/rendering/renderer_rd/shader_rd.cpp:286)
### ERROR: Condition "!shader_singleton->shader.version_is_valid(version)" is true.
   at: set_code (servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.cpp:171)
### ERROR: Condition "!shader" is true. Returning: RID()
   at: uniform_set_create (drivers/vulkan/rendering_device_vulkan.cpp:5361)
### ERROR: Condition "!us" is true.
   at: uniform_set_set_invalidation_callback (drivers/vulkan/rendering_device_vulkan.cpp:5835)

But when I pass INV_VIEW_MATRIX from vertex function with varying everything works
So I will use that until this error will fix