// Fork of "Day 405" by jeyko. https://shadertoy.com/view/ttVcRt
// 2021-01-27 11:17:18


const float slices = 350.;

const float aaSteps = 1.; // not really steps, it's the exponentially ^3 area growing area around the fragCoord

const float disp = .7;

const float width = 0.0004;

// asin(sin) is a triangle wave
#define sin(x) asin(sin(x))

float fun(float p, float py){

    //float f = sin(p + iTime + cos(py*0.05 + sin(p))*0.7)*sin(py*0.1 + iTime*0.2);
    py *= 170.;

    py += iTime*2.;
    float f = abs(sin(p*9. + sin(py*0.2 )*1.));

    f = pow(max(f,0.001),0.15);

    //f += (sin(py*0.1 + iTime + sin(p*6. + iTime)))*0.1;
    f += (sin(py*0.1 + iTime + sin(p*8. + iTime*.1 + sin(py*2.)*0.1)))*0.1;



    //f = cos(p*0.4- iTime + py)*cos(p*0.4*sin(p) + iTime)*(sin(py + iTime));
    //f = sin(p*0.5 + sin(py))*(cos(py*0.1 + iTime));
    /*
    f *= mix(
        smoothstep(0.,1.,abs(p + sin(py)*0.1)),
        smoothstep(0.,1.,abs(p + sin(py*0.3 + iTime)*0.1)),
        0.5 + sin(iTime*0.4 )*0.5
        );
    */
    return f*disp;
}



const float eps = 0.0004; // eps for derivative of graphing function

float graph(float y, float fn0, float fn1, float pixelSize){
  return smoothstep(pixelSize ,0.,
                    abs(fn0-y)/length(vec2((fn1-fn0)/eps,1.))- width);
}
float graphNoAbs(float y, float fn0, float fn1, float pixelSize){
  return smoothstep(pixelSize,0.,
                    -(fn0-y)/length(vec2((fn1-fn0)/eps,1.)) - width);
}


vec3 get(in vec2 fragCoord){
    vec2 uv = (fragCoord - 0.5*iResolution.xy)/iResolution.y;

    vec3 col = vec3(0);


    float pixelSize = dFdx(uv.x);

    for(float i = 0.; i < slices; i++ ){
        vec2 p = uv + vec2(0.,i/slices*2. - 0.6);

        //float funIdx = p.x*4. + sin(p.y*i/slices*2. + iTime)*1.5*sin(p.x - iTime);
        float funIdx = p.x;
        float funIdxY = i/slices;

        col -= graphNoAbs( p.y, fun(funIdx,funIdxY), fun(funIdx+eps,funIdxY), pixelSize);
        col = max(col,0.);
        col = mix(col, vec3(1), graph( p.y, fun(funIdx,funIdxY), fun(funIdx+eps,funIdxY ), pixelSize ));

    }


    col = 1. - col;
    return col;
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    vec3 col = vec3(0);


    for(float i =0.; i < aaSteps*aaSteps + min(float(iFrame),0.)   ; i++){
    	col += get(fragCoord + vec2(mod(i,aaSteps),floor(i/aaSteps))/aaSteps);
    }
    col /= aaSteps*aaSteps;


    col = max(col, 0.);
	//col = pow(col, vec3(0.4545));


    col = pow(col,vec3(0.4545));

    fragColor = vec4(col,1.0);
}