Add ability to include built-in include files

[BastiaanOlij]

This PR is a prelude to functionality we need for custom shader templates, but also has broader use in compositor effects.

This adds extra code so our include files are compiled along side the full template shader files. We can then include those in source and register them which enables us to use them in user shaders.

As part of this PR only 3 include files are actually exposed as a larger reorganisation will be needed before custom shader templates can be a thing.
For compositor effects however these can be useful includes. Right now we only have access to the scene data uniform but we'll be exposing more in the near future.

Note, this PR in godot demo projects has an example of how to use this in compositor effects:
godotengine/godot-demo-projects#1086

Here you can see that we're including our scene data UBO by including the scene data include file:

#include "godot/scene_data_inc.glsl"

layout(set = 0, binding = 0, std140) uniform SceneDataBlock {
	SceneData data;
	SceneData prev_data;
}
scene_data_block;

(the SceneDataBlock is not part of the include file so you can use your own set and binding as this will be likely different from the built in values).

Then in the compositor effect code you simply assign the existing UBO:

var scene_data := p_render_data.get_render_scene_data()
var scene_data_buffers: RID = scene_data.get_uniform_buffer()

var uniform:= RDUniform.new()
uniform.uniform_type = RenderingDevice.UNIFORM_TYPE_UNIFORM_BUFFER
uniform.binding = 0
uniform.add_id(scene_data_buffers)
var uniform_set := UniformSetCacheRD.get_cache(shader, 0, [uniform])

var compute_list := rd.compute_list_begin()
rd.compute_list_bind_uniform_set(compute_list, uniform_set, 0)

Now you have access to all the global scene data information such as projection matrices, view matrices, etc. in your compositor effect.

[BastiaanOlij]

Added a really crude demonstration of the compositor effects use case of this functionality here: godotengine/godot-demo-projects#1086

This should both work if you build the shader manually like in the post_proces_shader.gd example, as well as doing the include in a .glsl file. I'm assuming for real files they need a res::// prefix, else this means that our build in glsl include files have become reserved names.

As we lack some of the build in defines, it all does come with a bit of a manual (yet to be written), but for instance to include the scene data we get:

#version 450

#define MAX_VIEWS 2

#include "godot/scene_data_inc.glsl"

// Invocations in the (x, y, z) dimension.
layout(local_size_x = 8, local_size_y = 8, local_size_z = 1) in;

layout(set = 0, binding = 0, std140) uniform SceneDataBlock {
	SceneData data;
	SceneData prev_data;
}
scene_data_block;
...

Then in code we get:

var scene_data := p_render_data.get_render_scene_data()
var scene_data_buffers: RID = scene_data.get_uniform_buffer()

To retrieve our RID, and then obviously our uniform set:

var scene_data_uniform := RDUniform.new()
scene_data_uniform.uniform_type = RenderingDevice.UNIFORM_TYPE_UNIFORM_BUFFER
scene_data_uniform.binding = 0
scene_data_uniform.add_id(scene_data_buffers)
var uniform_set := UniformSetCacheRD.get_cache(shader, 0, [scene_data_uniform])

...

rd.compute_list_bind_uniform_set(compute_list, uniform_set, 0)

Now in the shader we can access the build in scene data uniform buffer (view in this case coming from our push constant):

mat4 inv_projection_matrix = scene_data_block.data.inv_projection_matrix_view[int(params.view)];

[BastiaanOlij]

Rebased and added some more code that is needed for custom shader templates.

[BastiaanOlij]

@clayjohn Would you mind reviewing this, I'd like to get this merged as the functionality added here is already useful even before we add custom shader templates.

[BastiaanOlij]

Forgot to put some extra info here after our rendering meeting a month ago.
Decision was made to change this PR so the include files are held within their own ShaderIncludeDB class.
Just haven't had time to do this yet.

[BastiaanOlij]

Rofl, edited the OP to include an example only to realise I had previously provided an example. A well, makes more sense in the OP. :)

This is ready for review again, with changes applied as discussed in rendering meeting from some time ago.

[BlueCube3310]

I've tested this locally and it works as expected. Looks good to me aside from some minor nitpicks

[clayjohn]

:) Reviewed in the rendering meeting

[Mickeon]

Suggested change

	Internal database of built in shader include files.
	Internal database of built-in shader include files.

[Mickeon]

Suggested change

	This object contains shader fragments from Godot's internal shaders. These can be used when access to internal uniform buffers and/or internal functions is required for instance when composing compositor effects or compute shaders. Only fragments for the current rendering device are loaded.
	This object contains shader fragments from Godot's internal shaders. These can be used when it is necessary to access to internal uniform buffers and/or internal functions, for example when composing compositor effects or compute shaders. Only fragments for the current rendering device are loaded.

[Mickeon]

Suggested change

	Returns [code]true[/code] if an include file with this name exists.
	Returns [code]true[/code] if an include file with the given [param filename] exists.

[Mickeon]

Suggested change

	Returns a list of built-in include files that are currently registered.
	Returns the list of built-in include files that are currently registered.

[Repiteo]

Thanks!

[Mickeon]

Merged a bit too soon with the "built in" typo but ah well

[BastiaanOlij]

h the "built in" typo but a

Shhhh, you can just fix it separately :P