de.glsl

#ifdef GL_ES
precision mediump float;
#endif

#extension GL_OES_standard_derivatives : enable

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


#define PI 3.1415926535898
float aspect_ratio = resolution.y / resolution.x;
float ray_scale = (1. / max(resolution.x, resolution.y)) * .47;

float de(vec3 p){
	float r =0.,power = 8.,dr = 1.;
	vec3 z = p;
	for(int i=0;i<10;i++){
		r = length(z);
		if(r > 4.) break;
		float theta = acos(z.z / r) ;//+ fract(t/20.) * 6.3;
		float phi = atan(z.y,z.x);
		
		dr = pow(r,power-1.)*power*dr+1.;
		float zr =  pow(r,power);
		theta = theta * power;
		phi = phi*power;
		z =  zr*vec3(sin(theta) * cos(PI),sin(phi) * sin(theta),cos(theta)) ;
		z += p;
		
	}
	
	return .5 * log(r) * r / dr;
	}

float kset(vec3 p) {
	p=abs(.5-fract(p*1.));
	float es, l=es=0.;
	for (int i=0;i<13;i++) {
		float pl=l;
		l=length(p);
		p=abs(p)/dot(p,p)-.5;
		es+=exp(-1./abs(l-pl));
	}
	return es;	
}

	
float trace(vec3 from, vec3 dir) {
	float l = 0.; 
	float d = 0.; 
	float e = 0.00001; 
	float it = 0.;
	
	for(int i=0;i<12;i++){
		d = de(from);
		
		from += d * dir;
		l += d;
		if(d<e) break;
		
		e = ray_scale * l;
		it++;	
	}	
	float f = 1. - (it / float(12));
	return  f;
}

vec3 map(vec3 p){
	return vec3(de(p));
}

vec3 calcNormal( in vec3 pos )
{
   vec3 eps = vec3( 0.0005, 0.0, 0.0 );
	vec3 nor = vec3(
	    map(pos+eps.xyy).x - map(pos-eps.xyy).x,
	    map(pos+eps.yxy).x - map(pos-eps.yxy).x,
	    map(pos+eps.yyx).x - map(pos-eps.yyx).x );
	return normalize(nor);
}

float calcAO( in vec3 pos, in vec3 nor )
{
	float occ = 0.0;
    float sca = 1.0;
    for( int i=0; i<5; i++ )
    {
        float hr = 0.01 + 0.12*float(i)/4.0;
        vec3 aopos =  nor * hr + pos;
        float dd = map( aopos ).x;
        occ += -(dd-hr)*sca;
        sca *= 0.95;
    }
    return clamp( 1.0 - 3.0*occ, 0.0, 1.0 );    
}


float softshadow( in vec3 ro, in vec3 rd, in float mint, in float tmax )
{
	float res = 1.0;
    float t = mint;
    for( int i=0; i<16; i++ )
    {
	vec3 p = vec3(de( ro + rd*t ));
	float h = p.x;
        res = min( res, 8.0*h/t );
        t += clamp( h, 0.02, 0.10 );
        if( h<0.001 || t>tmax ) break;
    }
    return clamp( res, 0.0, 1.0 );
}



vec3 light(vec3 rd,vec3 ro, float t ){
	
	vec3 col = vec3(0.5);
	
	vec3 pos = ro + t*rd;
        vec3 nor = calcNormal( pos );
	
	vec3 ref = reflect( rd, nor );
	float occ = calcAO( pos, nor );
	 
	vec3  lig = normalize( vec3(-0.4, 0.7, -0.6) );
	float amb = clamp( 0.5+0.5*nor.y, 0.0, 1.0 );
        float dif = clamp( dot( nor, lig ), 0.0, 1.0 );
        float bac = clamp( dot( nor, normalize(vec3(-lig.x,0.0,-lig.z))), 0.0, 1.0 )*clamp( 1.0-pos.y,0.0,1.0);
        float dom = smoothstep( -0.1, 0.1, ref.y );
        float fre = pow( clamp(1.0+dot(nor,rd),0.0,1.0), 2.0 );
		float spe = pow(clamp( dot( ref, lig ), 0.0, 1.0 ),16.0);
        
        dif *= softshadow( pos, lig, 0.02, 2.5 );
        dom *= softshadow( pos, ref, 0.02, 2.5 );

	vec3 lin = vec3(0.0);
        lin += 1.30*dif*vec3(1.00,0.80,0.55);
		lin += 2.00*spe*vec3(1.00,0.90,0.70)*dif;
        lin += 0.40*amb*vec3(0.40,0.60,1.00)*occ;
        lin += 0.50*dom*vec3(0.40,0.60,1.00)*occ;
        lin += 0.50*bac*vec3(0.25,0.25,0.25)*occ;
        lin += 0.25*fre*vec3(1.00,1.00,1.00)*occ;
	
	col = col*lin;

    	col = mix( col, vec3(0.8,0.9,1.0), 1.0-exp( -0.0002*t*t*t ) );
    
	return vec3( clamp(col,0.0,1.0) );
	
}



void main( void ) {

	vec2 tx = ( gl_FragCoord.xy / resolution.xy ) -.5 ;
	
	
	float a =  time*0.3 ;
	float sa = sin(a);
	float ca = cos(a);
	
	float fov  =  1.5;
	
	vec3 dir = vec3(tx.x * fov, tx.y * fov * aspect_ratio, 1.);
	
	dir.xy = vec2(dir.x * ca - dir.y * sa,dir.x * sa + dir.y * ca);
	dir.xz = vec2(dir.x * ca - dir.z * sa, dir.x  * sa + dir.z * ca); 
	
	vec3 cam = vec3(0.0,0.,-2.5 );
		cam.xz = vec2(cam.x * ca - cam.z * sa, cam.x * sa + cam.z * ca);
	
	float t = trace(cam,dir);
	
	
	 vec3 tot = vec3(0.0);
	if(t > 0.){
		
	
	vec3 col = light(cam,dir,t);
	
	
	 col = pow( col, vec3(0.4545) );

        tot += col;
	}
	
	 
	

	gl_FragColor = vec4( tot, 1.0 );

}