accumulate.comp

#version 450

// Copied from the color conversion shader where it gave the best performance.
#define WORKGROUP_SIZE 4
layout (local_size_x = WORKGROUP_SIZE, local_size_y = WORKGROUP_SIZE, local_size_z = 1) in;

layout (binding = 0, rgba8) uniform readonly image2D image_frame;
layout (binding = 1, rgba16) uniform image2D image_sample;
layout (push_constant) uniform push_constants {
    float weight;
};

// Transfer functions are the sRGB reference monitor EOTF of x^2.2, explicitly
//  not the piecewise functions.
//  https://en.wikipedia.org/wiki/SRGB#Transfer_function_(%22gamma%22)
//  definitions of terms: https://cie.co.at/e-ilv

// sRGB electro-optical transfer function
vec3 sRGB_EOTF(vec3 value)
{
    return pow(value, vec3(2.2));
}

void main() {
    ivec2 size = imageSize(image_frame);
    uint width = uint(size.x), height = uint(size.y);

    uint x = gl_GlobalInvocationID.x, y = gl_GlobalInvocationID.y;
    if (x >= width || y >= height)
        return;

    ivec2 coords = ivec2(x, y);

    vec4 frameColor = imageLoad(image_frame, coords);
    vec4 sampleColor = imageLoad(image_sample, coords);

    vec4 newColor = vec4(
        sampleColor.rgb + sRGB_EOTF(frameColor.rgb) * weight,
        sampleColor + frameColor * weight // alpha channel isn't encoded
    );
    imageStore(image_sample, coords, newColor);
}