Is there any way to access LIGHT in the fragment shader?

[yukikon]

Godot Version

4.2.1

Question

I was creating a fragment shader for adding a texture to the parts of my characters and objects in shadow, and I was wondering if there was a way to get the LIGHT value, the one available in the light shader, in the fragment shader?

I’m still a bit new to creating shaders so maybe there’s a better way of implementing this, but I’ve searched around and haven’t found a good solution. Any help would be appreciated!

[gertkeno]

You might be able to use a varying, but the docs say light is a function in part of the fragment shader so it can only be used to pass from void fragment() to void light(). Your best best is to find a way to adhere to this pipeline direction.

It’s also possible to send data from fragment to light processors using varying keyword. To do so you can assign it in the fragment and later use it in the light function.

shader_type spatial;

varying vec3 some_light;

void fragment() {
    some_light = ALBEDO * 100.0; // Make a shining light.
}

void light() {
    DIFFUSE_LIGHT = some_light;
}

Note that varying may not be assigned in custom functions or a light processor function like:

shader_type spatial;

varying float test;

void foo() {
    test = 0.0; // Error.
}

void vertex() {
    test = 0.0;
}

void light() {
    test = 0.0; // Error too.
}

This limitation was introduced to prevent incorrect usage before initialization

Shading language

[yukikon]

Thanks for the response! The shader works if I use a static light vector for both the fragment and light shader, however I want the texture added to the albedo with regard to the light level from multiple light sources, and a static vector can’t give that information. I also tried adjusting the albedo in the light shader but albedo is just a constant in the light shader, so I’m kind of at an impasse.

[gertkeno]

@gertkeno

void light() {
    DIFFUSE_LIGHT = some_light;
}

Maybe the keyword you are looking for is DIFFUSE_LIGHT instead of ALBEDO?

[yukikon]

This kind of works, the applied texture’s color still changes a bit depending on the color of the underlying texture but I’ll tweak it and see if I can make it look a bit better. Thanks for putting me on the right track.