PlainImageCompositor.comp

#version 450

layout (local_size_x = 15, local_size_y = 15, local_size_z = 1) in;
layout (set = 0, binding = 0, rgba8) uniform readonly image2D VDIsColor;
layout (set = 1, binding = 0, rgba8) uniform readonly image2D VDIsDepth;
layout (set = 2, binding = 0, rgba8) uniform image2D AlphaComposited; //TODO: put loadstore

vec2 decode(vec4 c){
    vec2 v = vec2(0.);

    int ir = int(c.r*255.);
    int ig = int(c.g*255.);
    int irg = ir*256 + ig;
    v.x = float(irg) / 256.;

    int ib = int(c.b*255.);
    int ia = int(c.a*255.);
    int iba = ib*256 + ia;
    v.y = float(iba) / 256.;

    v -= 128.;
    return v;
}

const vec4 bitEnc = vec4(1.,255.,65025.,16581375.);
const vec4 bitDec = 1./bitEnc;
float DecodeFloatRGBA (vec4 v) {
    return dot(v, bitDec);
}

float adjustOpacity(float a, float modifiedStepLength) {
    return 1.0 - pow((1.0 - a), modifiedStepLength);
}

void main() {
    int numInputSupersegments = 1;

    int frontSupersegment[50]; // which supersegment of this pixel are we currently looking at, for each process

    ivec2 opImageCoords  = imageSize(AlphaComposited);
    int numOutputSupersegments = 1;

    int numProcesses = opImageCoords.r / opImageCoords.g; //TODO: generalize for non square images

    for (int i = 0; i<numProcesses; i++) {
        frontSupersegment[i] = 0;
    }

    vec4 startDepth;
    vec4 endDepth;
    vec4 colour;

    float lowDepth;
    int lowIndex;

    vec4 compositedColor = vec4(0);

    for(int i = 0; i<numProcesses; i++) {

        startDepth = vec4(0);
        colour = vec4(0);
        lowDepth = 200.0;
        lowIndex = -1;

        for (int j = 0; j < numProcesses; j++) {
            if(frontSupersegment[j] >= numInputSupersegments) {
                continue;
            }

            vec4 curStartDepthRGBA = imageLoad(VDIsDepth, ivec2(gl_GlobalInvocationID.x, j * opImageCoords.g + gl_GlobalInvocationID.y)).rgba;
            float curStartDepth = DecodeFloatRGBA(curStartDepthRGBA);

            if(curStartDepth < lowDepth && curStartDepth != 0) {
                lowDepth = curStartDepth;
                lowIndex = j;
                startDepth = curStartDepthRGBA;
                colour = imageLoad(VDIsColor, ivec2(gl_GlobalInvocationID.x, j * opImageCoords.g + gl_GlobalInvocationID.y)).rgba;
            }
        }

        compositedColor.rgb = compositedColor.rgb + (1.0f - compositedColor.a) * colour.rgb * colour.a;
        compositedColor.a = compositedColor.a + (1.0f - compositedColor.a) * colour.a;

        if(lowIndex != -1) {
            frontSupersegment[lowIndex]++;
        }

    }

    //    vec4 compositedColor = vec4(0, 1, 0, 1);
    imageStore(AlphaComposited, ivec2(gl_GlobalInvocationID.x, gl_GlobalInvocationID.y), compositedColor);
}