#extension GL_OES_standard_derivatives : enable

precision highp float;

uniform float time;
uniform vec2 mouse;
uniform vec2 resolution;

#define hash(x) fract(sin(x)*43758.5453)
#define X(col) if(h<.5){\
		q=vec2(q.y,-q.x);\
	}\
	h=hash(h);\
	if(h<.5){\
		q=abs(q);\
		col+=smoothstep(.1,0.,min(q.x,q.y));\
	}else{\
		if(q.y<-q.x){\
			q.xy=-q.yx;\
		}\
		q-=.5;\
		col+=smoothstep(.1,0.,abs(length(q)-.5));\
	}

const float pi2=acos(-1.)*2.;

float hash21(vec2 p){
	return hash(dot(p ,vec2(12.9898,78.233)));
}

void rot3d(inout vec3 v,float a,vec3 ax){
	ax=normalize(ax);
	v=mix(dot(ax,v)*ax,v,cos(a))-sin(a)*cross(ax,v);
}

mat2 rot(float a){
	float s=sin(a),c=cos(a);
	return mat2(c,s,-s,c);
}

const float radius=.15;
const float floorHeight=-.12;
float lightTime=0.;
float map(vec3 p){
	float d,d1,d2;
	float h=hash21(floor(p.zx));
	
	vec3 q=p;
	q.zx=fract(q.zx)-.5;
	if(h<.5){
		q.zx=vec2(q.x,-q.z);
	}
	
	vec3 q1=q;
	q.x=abs(q.x);
	d1=length(q.xy)-radius;
	float grad=48.*radius*q.x*(q.x-.5);
	float tmp=length(vec2(abs(q.y-(q.x*q.x*(q.x-.75)*32.+2.)*radius)/sqrt(1.+grad*grad),q.z))-radius;
	d1=min(d1,tmp);
		
	q=q1;
	if(q.x<-q.z){
		q.zx=-q.xz;
	}
	q.zx-=.5;
	d2=length(vec2(length(q.zx)-.5,q.y))-radius;

	float a=1.;
	float ac=0.;
	for(int i=0;i<5;i++){
		q=(p+hash(float(i))*500.)*a;
		q+=sin(q*1.7)*2.;
		q=sin(q);
		ac+=q.x*q.y*q.z/a*.07;
		a*=2.;
	}
	h=hash(h);
	lightTime=time+h*pi2;
	d=mix(d1,d2,smoothstep(-.5,.5,sin(lightTime)));
	d+=ac;
	
	float df=p.y-floorHeight;
	d=min(d,df);
	d=mix(d,df,smoothstep(-.2,.2,-sin(time*.3)));
	
	return d;
}

vec3 calcN(vec3 p){
	vec2 e=vec2(.001,0);
	return normalize(vec3(map(p+e.xyy)-map(p-e.xyy),
			      map(p+e.yxy)-map(p-e.yxy),
			      map(p+e.yyx)-map(p-e.yyx)
			      ));
}

vec3 getC(vec3 p){
	vec3 col=vec3(0);
	if(p.y>floorHeight+.01){
		col+=vec3(.9,.7,.3);		
		return col;
	}
	
	vec2 q=p.zx*5.;
	float h=hash21(floor(q)*1.1523);
	q=fract(q)-.5;
	
	vec3 c1=vec3(0);
	vec2 q1=q;
	X(c1)
		
	vec3 c2=vec3(0);
	q=q1;
	h=hash(h);
	X(c2);
	
	col=mix(c1,c2,smoothstep(-.5,.5,sin(lightTime)));
	
	q=p.zx*.5;
	q=fract(q)-.5;
	if(q.x*q.y>0.){
		col=1.-col;
	}
	col=clamp(col,.05,.95);
	float red=smoothstep(.51,.49,abs(sin(lightTime)));
	col+=vec3(1,0,0)*red*100.;
	
	return col;
}

float shadow(vec3 rp,vec3 rd){
	float d;
	float h=.001;
	float res=1.;
	float c=.2;
	for(int i=0;i<30;i++){
		d=map(rp+rd*h);
		if(d<.001){
			return c;
		}
		res=min(res,16.*d/h);
		h+=d;
	}
	return mix(c,1.,res);
}

float fs(float f0,float c){
	return f0+(1.-f0)*pow(1.-c,5.);
}

vec3 march(inout vec3 rp,inout vec3 rd,inout bool hit,inout vec3 ra,int itr){
	vec3 col=vec3(0);
	float t=0.;
	hit=false;
	
	for(int i=0;i<100;i++){
		if(i>=itr||t>30.){
			break;
		}
		float d=map(rp+rd*t);
		if(abs(d)<.0001){
			hit=true;
			break;
		}
		t+=d*.9;
	}
	rp+=rd*t;
	
	vec3 ld=normalize(vec3(-3,3,-1));
	vec3 al=getC(rp);
	vec3 n=calcN(rp);
	vec3 ref=reflect(rd,n);
	float diff=max(dot(ld,n),0.);
	float spec=pow(max(dot(reflect(ld,n),rd),0.),20.);
	float fog=exp(-t*t*.005);
	float sh=shadow(rp+.01*n,ld);
	float f0=0.8;
	float lp=10.;
	float m=0.9;
	col+=al*diff*sh*(1.-m)*lp;
	col+=al*spec*sh*m*lp;
	col=mix(vec3(1),col,fog);
	
	col*=ra;
	ra*=al*fs(f0,dot(ref,n))*fog;
	
	rp+=.01*n;
	rd=ref;
	
	return col;
}

vec3 acesFilm(vec3 x) {
	const float a = 2.51;
	const float b = 0.03;
	const float c = 2.43;
	const float d = 0.59;
	const float e = 0.14;
	return clamp((x * (a * x + b)) / (x * (c * x + d) + e), 0., 1.);
}

#define ihash(x,n) floor(hash(x)*float(n))
float in1d(float x,int n){
  float i=floor(x);
  float s=.1;
  float u=smoothstep(.5-s,.5+s,fract(x));
  return mix(ihash(i,n),ihash(i+1.,n),u);
}

void main( void ){
	vec2 uv=(gl_FragCoord.xy*2.-resolution)/min(resolution.x,resolution.y);
	vec3 col=vec3(0);
	
	vec3 cp=vec3(0,1.,-time);
	vec3 rd=normalize(vec3(uv,-2.+dot(uv,uv)*.3));
	
	cp.x+=in1d(cp.z*.33-550.5,10);
	cp.y+=in1d(cp.z*.39-61.,5);
	
	rot3d(rd,cp.y*.3,vec3(1,0,0));
	
	vec3 rp=cp;
	vec3 ra=vec3(1);
	bool hit=false;
	col+=march(rp,rd,hit,ra,100);
	if(hit){
		col+=march(rp,rd,hit,ra,30);
	}
	if(hit){
		col+=march(rp,rd,hit,ra,30);
	}
	
	col=acesFilm(col);
	col=pow(col,vec3(1./2.2));
	
	gl_FragColor = vec4(col,1);
}