jfa_2d.glsl

vec4 StepJFA (in vec2 fragCoord, in float level)
{
    level = clamp(level-1.0, 0.0, c_maxSteps);
    float stepwidth = floor(exp2(c_maxSteps - level)+0.5);
    
    float bestDistance = 9999.0;
    vec2 bestCoord = vec2(0.0);
    vec3 bestColor = vec3(0.0);
    
    for (int y = -1; y <= 1; ++y) {
        for (int x = -1; x <= 1; ++x) {
            vec2 sampleCoord = fragCoord + vec2(x,y) * stepwidth;
            
            vec4 data = texture( iChannel0, sampleCoord / iChannelResolution[0].xy);
            vec2 seedCoord;
            vec3 seedColor;
            DecodeData(data, seedCoord, seedColor);
            float dist = length(seedCoord - fragCoord);
            if ((seedCoord.x != 0.0 || seedCoord.y != 0.0) && dist < bestDistance)
            {
                bestDistance = dist;
                bestCoord = seedCoord;
                bestColor = seedColor;
            }
        }
    }
    
    return EncodeData(bestCoord, bestColor);
}