Add support for struct uniforms in shaders

[Chaosus]

• Closes Add support for uniform structs in the shader language godot-proposals#3569

Notes:

• This version uses a Dictionary type for the uniform type. I did not find the other type which fits better for this. Still, the interface sucks and do not auto-reflect the changes made in a shader struct, but at least It's something (user need to manually adds members to it and change their types) -> (UPDATE: Dictionary in the inspector now reflects the changes from the shader).

• Structs needs to be declared before MaterialUniform in order to they can be used for uniforms, that's why I pushed them under #STRUCT statements inside each shader file.

• There are few limitations with this implementation, currently:

  • You cannot assign a default value, e.g:

   struct Foo {
   	vec3 v;
   };
   uniform Foo foo = Foo(vec3(0, 1, 0));
  

  • instance/global scope initializers are not supported

• Arrays of common datatype in struct are supported (you can pass an array of conformal type):

• Compatibility renderer is supported

• set_shader_parameter via script is supported (You need to pass a dictionary, remember).

• UPDATE: You can declare an array of struct, e.g:

   struct Foo {
   	vec4 v;
   };
   uniform Foo foos[2];
  

• UPDATE 2: You can use a struct inside a struct, e.g.:

   struct A {
   	float t;
   };
   struct B {
   	A a;
   };
   uniform B b;
  

@QbieShay, @Calinou If you're interested to check and play with it, you're welcome.

[RadiantUwU]

I've tested the uniform struct out, it's a wildly amazing idea, but it doesn't work.
It seems to be either writing 2 floats before the actual vec4, or reading 2 floats after the vec4

shader_type spatial;
render_mode unshaded;

instance uniform vec3 color : source_color;

struct RayColorIdk {
	vec3 orig;
	vec3 dir;
	vec4 color;
};
uniform RayColorIdk ray;

void fragment() {
	ALBEDO = ray.color.rgb;
	//EMISSION = color;
}

This is the entirety of the code used in the example, hope this helps!

[RadiantUwU]

Another issue spotted is me being able to delete fields or add fields to that dictionary. Other than that, amazing!

[Chaosus]

I've tested the uniform struct out, it's a wildly amazing idea, but it doesn't work.

Yeah, this is because that struct layout is not aligned to 16 bytes, if you add a member to it, it will work:

struct RayColorIdk {
	vec3 orig;
	float reserved;
	vec3 dir;
	float reserved2;
	vec4 color;
};

We should probably add reserved members internally.

Another issue spotted is me being able to delete fields or add fields to that dictionary.

Well, this is ok, at least for now, as noted in the topic description. If the member is absent, the default value (0) is passed to the compiler.

[Chaosus]

It seems to be either writing 2 floats before the actual vec4, or reading 2 floats after the vec4

@RadiantUwU I think I've fixed it!

[RadiantUwU]

RadiantUwU@6d9cfab
This would fix the issue of the tests failing. (Line numbers are different for me since this is another godot fork)

[Chaosus]

Also fixed the dictionary in the inspector to reflect the changes from the shader.

[RadiantUwU]

What happens if the user has an initialization for the struct?

Like for example, having a default for the struct

struct A {
    vec3 col;
    float alph;
};
uniform A struct_uniform = A(vec3(1.0),1.0);

Wouldn't this just skip over it?

[Chaosus]

It's currently not implemented as stated in the topic header.

[RadiantUwU]

Looks fine for the most part, i'd recommend in a future pull request to implement a way for developers to have a way of setting default values.

LGTM
Can't wait to see this into 4.4 stable

[Chaosus]

Looks fine for the most part, i'd recommend in a future pull request to implement a way for developers to have a way of setting default values.

It's a draft pull request that mean I will add new features and bug fixes until a certain point in time. Don't worry about default values, it's on the list to implement.

[Chaosus]

Added support for the structs inside structs (they will be parsed as mixed Array/Dictionary hierarchy):