Reading VIEWPORT_SIZE in light() function breaks spatial shader.

[EMBYRDEV]

Godot version

4.0.2.stable

System information

Windows 11, Vulkan, RTX2070 Super

Issue description

Reading from VIEWPORT_SIZE in the light() function causes spatial shader to break and renders as default white.

Steps to reproduce

when line 51 is present the fails to compile with the following message in the output log but no compilation errors.

servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.cpp:171 - Condition "!shader_singleton->shader.version_is_valid(version)" is true.
  drivers/vulkan/rendering_device_vulkan.cpp:5361 - Condition "!shader" is true. Returning: RID()
  drivers/vulkan/rendering_device_vulkan.cpp:5835 - Condition "!us" is true.

commenting out line 51 solves this issue.

The documentation states that VIEWPORT_SIZE should be available to the light() function.

Minimal reproduction project

N/A

[clayjohn]

Related to #76556 We need to make sure that the light builtins are properly exposed in the light shader with the appropriate names (the variables are likely already available, they just need to be renamed)

[So-Yu-Him]

@clayjohn Hi, I am a newbee to open source projects and currently being a computer science student in HKUST, I want to gain more project experiences before graduation so I want to help for open source projects, I am willing to learn new techniques and help with this issue. Can you assign this issue to me and give me more information about it? Do I need to fix #76556 before fixing this issue?

[Calinou]

Can you assign this issue to me

For future reference, we only use the assignees feature for core contributors (and we don't always use it in the first place). Since contributors can leave at any time for any reason, we'd rather avoid a situation where nobody is working on an issue because it's assigned to someone who is no longer active.

[clayjohn]

@clayjohn Hi, I am a newbee to open source projects and currently being a computer science student in HKUST, I want to gain more project experiences before graduation so I want to help for open source projects, I am willing to learn new techniques and help with this issue. Can you assign this issue to me and give me more information about it? Do I need to fix #76556 before fixing this issue?

You do not need to fix #76556 before fixing this issue. The light shader code is defined here:

godot/servers/rendering/renderer_rd/shaders/scene_forward_lights_inc.glsl

Line 42 in b0b2308

void light_compute(vec3 N, vec3 L, vec3 V, float A, vec3 light_color, bool is_directional, float attenuation, vec3 f0, uint orms, float specular_amount, vec3 albedo, inout float alpha,

You can see here the variables that are renamed to be compatible with the names expected by the light shader:

godot/servers/rendering/renderer_rd/shaders/scene_forward_lights_inc.glsl

Lines 71 to 75 in b0b2308

	mat4 inv_view_matrix = scene_data_block.data.inv_view_matrix;
	vec3 normal = N;
	vec3 light = L;
	vec3 view = V;

Here you can see that VIEWPORT_SIZE is translated into ``scene_data.viewport_size:
https://github.com/godotengine/godot/blob/b0b23082c4d8cdcf20c090159f33726317504bdc/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.cpp#LL591C6-L591C6

So you need to ensure that scene_data.viewport_size is available in the shader at the appropriate time.