// Chroma Fragment Shader
// (Same as textured_chroma.fsh but isn't restricted to textured elements)

#version 120

uniform float chromaSize;
uniform float timeOffset;
uniform float saturation;
uniform bool forwardDirection;

varying vec4 originalColor;

float rgb2b(vec3 rgb) {
    return max(max(rgb.r, rgb.g), rgb.b);
}

vec3 hsb2rgb_smooth(vec3 c) {
    vec3 rgb = clamp(abs(mod(c.x * 6.0 + vec3(0.0, 4.0, 2.0), 6.0) - 3.0) - 1.0, 0.0, 1.0);
    rgb = rgb * rgb * (3.0 - 2.0 * rgb); // Cubic smoothing
    return c.z * mix(vec3(1.0), rgb, c.y);
}

void main() {
    // Determine the direction chroma moves
    float fragCoord;
    if (forwardDirection) {
        fragCoord = gl_FragCoord.x - gl_FragCoord.y;
    } else {
        fragCoord = gl_FragCoord.x + gl_FragCoord.y;
    }

    // The hue takes in account the position, chroma settings, and time
    float hue = mod(((fragCoord) / chromaSize) - timeOffset, 1.0);

    // Set the color to use the new hue & original saturation/value/alpha values
    gl_FragColor = vec4(hsb2rgb_smooth(vec3(hue, saturation, rgb2b(originalColor.rgb))), originalColor.a);
}