small raymarcher. nothing fancy

tiny-raymarcher.frag

#ifdef GL_ES
precision mediump float;
#endif

uniform float time;
uniform vec2 resolution;
#define PI 3.1415926535898
#define EPS 0.01
const float clipFar = 16.0;

mat2 rot2( float angle ) {  float c = cos( angle );  float s = sin( angle );  return mat2( c, s,-s, c); }
float bump(vec3 p) { return sin(p.x*PI*.25)*sin(p.y*PI*.25)*sin(p.z*PI*2.5);}

float map(vec3 p) {
  vec3 p2 = p;
  p.xy *= rot2( p.z * PI/6. + time*PI/2. );
  float b = bump(p*PI/12.)*.5;
  return length(p.xy + b) - clipFar;
}
void main( void ) {
  vec2 uv = (2.0*gl_FragCoord.xy/resolution.xy - 1.0) * vec2(resolution.x/resolution.y, 1.0);
  vec3 lookAt   = vec3(0,0, time/6.);
  vec3 camPos   = lookAt + vec3(0, 0, lookAt.z - 12.0);
  vec3 lightPos = lookAt + vec3(0, 0, lookAt.z - 0.0);
  vec3 forward = normalize(camPos);
  vec3 right = vec3(forward.z, 0., -forward.x );
  vec3 up = cross(forward, right);
  vec3 rd = normalize(forward + uv.x*right + uv.y*up);
  rd.xy *= rot2(time * PI / 9.);
  rd.yz *= rot2(time * PI / 18.);
  float t = 0.0;
  for (int i = 0 ; i < 120; i++) {
    float k = map(camPos + rd * t);
    t += k;
    // t += k * 0.35;
    if ((k < 0.0) || (t > clipFar)) {
      break;
    }
  }
  vec3 final  = vec3(0);
  vec3 p = camPos + rd * t;
  vec3 normal = normalize(vec3(
    map(vec3(p.x+EPS,p.y,p.z)) - map(vec3(p.x-EPS,p.y,p.z)),
    map(vec3(p.x,p.y+EPS,p.z)) - map(vec3(p.x,p.y-EPS,p.z)),
    map(vec3(p.x,p.y,p.z+EPS)) - map(vec3(p.x,p.y,p.z-EPS))
  ));
  vec3 lightDirection = normalize(lightPos - p);
  vec3 eyeDirection = normalize(camPos - p);
  final += 0.05 + 0.95 * max( 0.0, dot(normal, lightDirection) );
  final += pow(max( 0.0, dot(reflect(-lightDirection, normal), eyeDirection) ), 112.0);
  final.rg *= rot2(p.z*PI/6.);
  final *= 3.;
  // final *= fract(p);
  // gl_FragColor = vec4(clamp(mix(final, .2*vec3(.96,.9,.92), t/clipFar), 0.0, 1.0), 1.0);
  gl_FragColor = vec4(pow(final, vec3(1.0 / .6)) , 1.0);
}