Hw42

// Title: HW4
// Author: Iris
// Course: ShaderArt (DIGF-3011, Winter 2022)

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_mouse;
uniform vec2 u_resolution;
uniform float u_time;


// calculateHue()
// select a color from a collection of 6 based on a percentage
// returns a RGB color

// random()
// by Patricio Gonzalez-Vivo
float random (vec2 st) {
    return fract(sin(dot(st.xy,
                         vec2(12.9898,78.233)))*
        43758.5453123);
}

float map(float value, float min1, float max1, float min2, float max2) {
  return min2 + (value - min1) * (max2 - min2) / (max1 - min1);
}

vec3 calculateHue(vec3 colors[3], float pct){

    pct = fract(pct);

    vec3 result = vec3(0.0); // Define the result so that we don't return nothing by accident

    float numberOfSections = 3.; // Number of sections (maximum of 12)

    for (int position = 0; position <= 3; position ++){                 // Loops through the following code 12 times
        float leftPosition = float(position) / numberOfSections;        // Defines the left most position of the current section you're in
        float rightPosition = float(position) + 1. / numberOfSections;  // Defines the right most position of the current section you're in
        if (pct > leftPosition && pct <= rightPosition){                // Checks what section of the screen you are in (divided into numberOfSections)
            result = colors[position];                                  // Colors your section with the appropriate colour
        }
    }

    return result;
}

vec3 rgb_normalize( int r, int g, int b){
    return vec3(float(r)/255., float(g)/255., float(b)/255.);
}

void main (void) {

    vec2 st = gl_FragCoord.xy/u_resolution.xy;


    vec3 colors[3];
    // DEFINE YOUR COLOURS FOR THE TOP ROW HERE
    colors[0] = rgb_normalize(128, 0, 32);
    colors[1] = rgb_normalize(125, 112, 152);
    colors[2] = rgb_normalize(255, 0, 0);

    vec3 color = vec3(0);

    float row = 1.0 - st.y;
    row = floor( row * 3.0); // Split the screen into 4 rows

    // calculate the brightness based on the cell index using map()
    // this creates steps for brightness: 0., 0.25, 0.5, 0.75, 1.0
    float minBri = 0.3;
    float brightness = map(abs(row), 0., 4., 1., minBri );
    brightness *= map(abs(row), 0., 4., 1., minBri );

    if( row == 0.0){
        // SHOW THE TOP ROW
        color = calculateHue(colors, st.x*-1.);
    } else if( row == 1.0 ){
        // SHOW THE FIRST MIDDLE ROW
        color = calculateHue(colors, st.x-1.*tan(u_time)/3.);

    } else if( row == 2.0 ){
        // SHOW THE SECOND MIDDLE ROW
        color = calculateHue(colors, random(st*u_time/8.));
    }



    gl_FragColor = vec4(color,1.0);
}