Week3 HW2

// Author: Jeremy
//Editor: Ziqi
// Course: ShaderArt (DIGF-3011, Winter 2022)
// Title: LiveCode_Grid

#ifdef GL_ES
precision mediump float;
#endif

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

float sdSegment( in vec2 p, in vec2 a, in vec2 b )
{
    vec2 pa = p-a, ba = b-a;
    float h = clamp( dot(pa,ba)/dot(ba,ba), -0.192, 1.536 );
    return length( pa - ba*h );
}

vec3 hsb2rgb( in 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);
    return c.z * mix( vec3(1.000,0.975,0.955), rgb, c.y);
}


void main() {
    float change = abs(sin(u_time));//the change is from thebookofshaders 

    // normalized coordinates
    vec2 st = gl_FragCoord.xy/u_resolution.xy;
    st.x *= u_resolution.x/u_resolution.y;
    
    vec2 st0 = st;
    float circ2 = distance( st, vec2(0.790,0.470));
    circ2 = step( 0.256, circ2);
    
    st *= 10.0; // 0...10
    
    vec2 cellIndex = floor(st);
    st = fract( st); // 1.3 => 0.3
    
    
    if( mod(cellIndex.y, 2.) == 0.0){
    	st = st0;
        st.x -= -0.134;
        st *= 10.*change;
        cellIndex = floor(st);
        st = fract( st); // 1.3 => 0.3
    }
    
    
    vec3 color = vec3( st, 0);
    
    float circ1 = distance( st, vec2(0.5, 0.5));
    circ1 = 1.0-step(.624, circ1);
    
    // remainder after a division operation
    // 1 % 2 => 1
    // 2 % 2 => 0
    // 3 % 2 => 1
    // 4 % 2 => 0
    // 5 % 2 => 1
    // 6 % 2 => 0
    
    if( mod(cellIndex.x, 2.) == 0.){
        
        if( mod(cellIndex.y, 2.) == 0.){
            color = vec3( change, change, change )*circ1;
        } else {
            color = vec3(1.000,0.784,0.002)*circ1;
        }

    } else {
        
        if( mod(cellIndex.y, 2.) == 0.){
            color = vec3(0.420,0.565,1.000)*circ1;
        } else {
            color = vec3( 0.0, 1.0, 1. )*circ1;
        }
        
        
    }
    
    // calculate the color in HSB space
        vec3 hsb = vec3( st.y - u_time*1.168, 0.824, 0.632);
    
    
        float line = sdSegment( st, vec2(change,0.810), vec2(0.480,change));
            color = mix( color, hsb2rgb(hsb), line );

    


    // display the color for the pixel
    gl_FragColor = vec4(color, 1.0); 
}