fractal_test4.glsl

// Tutorial from https://www.youtube.com/watch?v=Cfe5UQ-1L9Q
// Thanks iq!
// Shadertoy defines

#define O gl_FragColor
#define U gl_FragCoord.xy
#define iGlobalTime iTime
#define AA 1.
#define R iResolution.xy
float Mx() 
{
    return iMouse.x / iResolution.x;
}

float My()
{
    return iMouse.y / iResolution.y;
}

float smin( in float a, in float b, float k )
{
    float h = max( k - abs(a-b), 0.0 );
    return min(a,b) - h*h/(k*4.0);
}

float smax( in float a, in float b, float k )
{
    float h = max( k - abs(a-b), 0.0 );
    return max(a,b) + h*h/(k*4.0);
}

mat3 rotateZ(float angle) {
	float c = cos(angle), s = sin(angle);
    return mat3(c,-s,0,s,c,0,0,0,1);
}

mat3 rotateY(float angle) {
	float c = cos(angle), s = sin(angle);
    return mat3(c, 0, -s, 0, 1, 0, s, 0, c);
}

float sdSphere(vec3 p, float r) {
	return length(p) - r;    
} 

// from iq
float sdPlane(in vec3 p, in vec4 n)
{
  return dot(p,n.xyz) + n.w;
}

// from iq
float sdBox( vec3 p, vec3 b )
{
  vec3 d = abs(p) - b;
  return length(max(d,0.0));
        
}

// https://github.com/HackerPoet/MarbleMarcher/blob/master/assets/frag.glsl
vec3 boxFold(vec3 z, vec3 r) {
	return clamp(z.xyz, -r, r) * 2.0 - z.xyz;
}

// http://www.fractalforums.com/fragmentarium/fragmentarium-an-ide-for-exploring-3d-fractals-and-other-systems-on-the-gpu/15/
void sphereFold(inout vec3 z, inout float dz) {
    
    float fixedRadius2 = 1.3;
    float minRadius2 = 0.1;
	float r2 = dot(z,z);
	if (r2< minRadius2) {
		float temp = (fixedRadius2/minRadius2);
		z*= temp;
		dz*=temp;
	} 
    else if (r2<fixedRadius2) {
		float temp =(fixedRadius2/r2);
		z*=temp;
		dz*=temp;
	}
}

// https://github.com/HackerPoet/MarbleMarcher/blob/master/assets/frag.glsl
vec3 mengerFold(vec3 z) {
	float a = min(z.x - z.y, 0.0);
	z.x -= a;
	z.y += a;
	a = min(z.x - z.z, 0.0);
	z.x -= a;
	z.z += a;
	a = min(z.y - z.z, 0.0);
	z.y -= a;
	z.z += a;
    return z;
}

float getRotation(float time) 
{
    return 0.;
}

vec2 getOffset(float time) 
{
    float frames = 5.;
    time = mod(time, frames);

    float it = floor(time),
          ft = fract(time);
    
    vec2 p1 = vec2(0.04, 0.12);
    vec2 p2 = vec2(0.25, 0.25); 
    vec2 p3 = vec2(0.12, 0.17); 
    vec2 p4 = vec2(0.05, 0.17); 
    vec2 pl = vec2(0.04, 0.12);
 
    vec2 pos = pl;

    if(it < 0.5)       pos = mix(pl, p1, smoothstep(0.0, .1, ft));
    else if(it < 1.5)  pos = mix(p1, p2, smoothstep(0.6, 0.8, ft));
    else if(it < 2.5)  pos = mix(p2, p3, smoothstep(0.5, .6, ft));
    else if(it < 3.5)  pos = mix(p3, p4, smoothstep(0.0, .1, ft));
    else if(it < 4.5)  pos = mix(p4, pl, smoothstep(0.0, .1, ft));

    return pos;
}

// http://blog.hvidtfeldts.net/index.php/2011/11/distance-estimated-3d-fractals-vi-the-mandelbox/
vec2 DE(vec3 z, float time)
{
    z *= rotateY(getRotation(time));
    float Iterations = 14.;
    float Scale = 2.6;
    vec2 of = getOffset(time);
	vec3 offset = z*10.*vec3(of.x, 0, of.y) -.5;
	float dr = 1.0;
    float trap = 99.;
	for (float n = 0.; n < Iterations; n++) {
        
        //z = boxFold(z, vec3(1.4));       // Reflect
        //z = mengerFold(z);

        z.xz = -z.zx;
        z.yx = -z.xy;
		
        z = boxFold(z, vec3(1));       // Reflect
        sphereFold(z, dr);    // Sphere Inversion
		
        z=z*Scale + offset;  // Scale & Translate
        
        dr = dr*abs(Scale)+1.0;
        trap = min(trap, length(abs(z)));
	}
	float r = length(z);
	return vec2(r/abs(dr), trap);
}

vec2 map( in vec3 pos, float time ) 
{
    vec2 d1 = DE(pos - vec3(0,0,0), time);
    return d1;
}

vec3 calcNormal( in vec3 pos, float t ) 
{
    vec2 e = vec2(0.00001, 0.0);
    return normalize( vec3(map(pos+e.xyy,t).x-map(pos-e.xyy,t).x,
                           map(pos+e.yxy,t).x-map(pos-e.yxy,t).x,
                           map(pos+e.yyx,t).x-map(pos-e.yyx,t).x ) );
}

float castShadow( in vec3 ro, vec3 rd, float time )
{
    float res = 1.0;
    float t = 0.00;
    for( int i=0; i<100; i++ )
    {
        vec3 pos = ro + t*rd;
        float h = map( pos, time ).x;
        res = min( res, 16.0*h/t );
        if ( res<0.01 ) break;
        t += h;
        if( t > 10.0 ) break;
    }

    return clamp(res,0.0,1.0);
} 

vec2 castRay( in vec3 ro, vec3 rd, float time )
{
    float m = -1.0;
    float t = 0.0;
    for( int i=0; i<100; i++ )
    {
        vec3 pos = ro + t*rd;

        vec2 h = map( pos, time );
        m = h.y;
        if( h.x<0.00075 )
            break;
        t += h.x;
        if( t>20.0 )
            break;
    } 
    if( t>20.0 ) m=-1.0;
    return vec2(t,m);
}


vec3 camPos(float time) 
{
    float frames = 5.;
    time = mod(time, frames);

    float it = floor(time),
          ft = fract(time);
    
    vec3 p1 = vec3(-0.25, 0, 0.2);
    vec3 p2 = vec3(0.2, 0, 0.2); 
    vec3 p3 = vec3(-.4, -0.3, 0.6); 
    vec3 p4 = vec3(-.3, 0.2, 0.4); 
    vec3 pl = vec3(-0.42, -0.05, 0.17);
 
    vec3 pos = pl;

    if(it < 0.5)       pos = mix(pl, p1, smoothstep(0.0, 1.0, ft));
    else if(it < 1.5)  pos = mix(p1, p2, smoothstep(0.0, 1.0, ft));
    else if(it < 2.5)  pos = mix(p2, p3, smoothstep(0.0, 1.0, ft));
    else if(it < 3.5)  pos = mix(p3, p4, smoothstep(0.0, 1.0, ft));
    else if(it < 4.5)  pos = mix(p4, pl, smoothstep(0.0, 1.0, ft));


    return pos * 2.0;
}

mat3 camRotation(float time)
{
    float frames = 2.;
    float it = floor(time),
          ft = fract(time);
 
    float angleY = 3.*cos(time);
    float angleZ = sin(time);

    float angleY1 = 0.;
    float angleZ1 = 0.;

    mat3 ry = rotateY(angleY);
    mat3 rz = rotateZ(angleZ);
    return ry * rz;
}
 
void main() {

    float time = iTime;
    //time = 4.5;
    //time = 3.;
    time /= 16.;

    vec3 col = vec3(0);
    vec3 res = vec3(0);
    
    for(float aax=0.; aax < AA; aax++)
    for(float aay=0.; aay < AA; aay++)
    {
        vec2 p = (2.*(U + vec2(aax, aay) / AA)-R)/R.y;
        
        mat3 rot = camRotation(time);

        vec3 ta = vec3(0,0,3) * rot;
        vec3 ro = camPos(time);

        //ta += ro;
        
        vec3 ww = normalize( ta-ro );
        vec3 uu = normalize( cross(ww, vec3(0,1,0)) );
        vec3 vv = normalize( cross(uu,ww) );

        vec3 rd = normalize( p.x*uu + p.y*vv + 1.8*ww );
 
        vec3 col = vec3(0.0);

        vec2 tm = castRay(ro, rd, time); 

        if( tm.x < 20. )
        {
            float t = tm.x;
            vec3 pos = ro + t*rd;
            vec3 nor = calcNormal(pos, time);

            vec3 mate = vec3(0.18); 
            mate = cos(vec3(0,1,1.5) + tm.y*1.2 - iTime/2.) *.5 + .5;

            mat3 sunRot = rotateY(1.9);
            vec3 sun_dir = normalize( vec3(5,0.05,-2) * sunRot );
            float sun_dif = clamp( dot(nor,sun_dir),0.0,1.0); 
            float sun_sha = 0.75*castShadow( pos+nor*0.001, sun_dir, time );
            float sky_dif = clamp( 0.5 + 0.5*dot(nor,vec3(0.0,1.0,0.0)), 0.0, 1.0);
            float bou_dif = clamp( 0.5 + 0.5*dot(nor,vec3(0.0,-1.0,0.0)), 0.0, 1.0);

            col  = 0.25*mate*vec3(5.0,4.5,4.0)*sun_dif*sun_sha;
            //col += mate*vec3(0.5,0.6,0.6)*sky_dif;
            col += 0.2*mate*vec3(0.5,0.6,0.6)*bou_dif;
        }

        res += clamp(col, 0.0, 1.0);
    }

    col = pow( res/(AA*AA), vec3(0.4545) );
    
    O = vec4(col, 1.0);
}