9_3_smoothMin

Code 9.3, Figure 9.7:

9_3_smoothMin.frag

#version 300 es precision highp float; precision highp int; out vec4 fragColor; uniform float u_time; uniform vec2 u_resolution; float sphereSDF(vec3 p, vec3 cent, float rad){ return distance(p, cent) - rad; } float smin(float a, float b, float k){ float h = clamp(0.5 - 0.5 * (b - a) / k, 0.0, 1.0); return mix(a, b, h) - k * h * (1.0 - h); } float sceneSDF(vec3 p){ float[3] smallS, bigS; for(int i = 0; i < 3; i ++ ){ smallS[i] = sphereSDF(p, vec3(float(i - 1), sin(u_time), 0.0), 0.3); bigS[i] = sphereSDF(p, vec3(float(i - 1), 0.0, 0.0), 0.4); } float cap = smin(smallS[0], bigS[0], 0.1); float cup = smin(smallS[1], bigS[1], 0.3); float minus = smin(smallS[2], bigS[2], 0.5); return min(min(cap, cup), minus); } vec3 gradSDF(vec3 p){ float eps = 0.0001; return normalize(vec3( sceneSDF(p + vec3(eps, 0.0, 0.0)) - sceneSDF(p + vec3(-eps, 0.0, 0.0)), sceneSDF(p + vec3(0.0, eps, 0.0)) - sceneSDF(p + vec3(0.0, - eps, 0.0)), sceneSDF(p + vec3(0.0, 0.0, eps)) - sceneSDF(p + vec3(0.0, 0.0, - eps)) )); } void main(){ vec2 p = (gl_FragCoord.xy * 2.0 - u_resolution) / min(u_resolution.x, u_resolution.y); vec3 cPos = vec3(0.0, 0.0, 2.0); vec3 cDir = vec3(0.0, 0.0, - 1.0); vec3 cUp = vec3(0.0, 1.0, 0.0); vec3 cSide = cross(cDir, cUp); float targetDepth = 1.0; vec3 lDir = vec3(0.0, 0.0, 1.0); vec3 ray = cSide * p.x + cUp * p.y + cDir * targetDepth; vec3 rPos = cPos + ray; ray = normalize(ray); fragColor.rgb = vec3(0.0); for(int i = 0; i < 50; i ++ ){ if (sceneSDF(rPos) > 0.001){ rPos += sceneSDF(rPos) * ray; } else { float amb = 0.1; float diff = 0.9 * max(dot(normalize(lDir), gradSDF(rPos)), 0.0); vec3 col = vec3(1.0); fragColor.rgb = col * (diff + amb); break; } } fragColor.a = 1.0; }

#version 300 es
precision highp float;
precision highp int;
out vec4 fragColor;
uniform float u_time;
uniform vec2 u_resolution;

float sphereSDF(vec3 p, vec3 cent, float rad){
  return distance(p, cent) - rad;
}

float smin(float a, float b, float k){
  float h = clamp(0.5 - 0.5 * (b - a) / k, 0.0, 1.0);
  return mix(a, b, h) - k * h * (1.0 - h); 
}

float sceneSDF(vec3 p){
  float[3] smallS, bigS;
  for(int i = 0; i < 3; i ++ ){
    smallS[i] = sphereSDF(p, vec3(float(i - 1), sin(u_time), 0.0), 0.3);
    bigS[i] = sphereSDF(p, vec3(float(i - 1), 0.0, 0.0), 0.4);
  }
  float cap = smin(smallS[0], bigS[0], 0.1);
  float cup = smin(smallS[1], bigS[1], 0.3);
  float minus = smin(smallS[2], bigS[2], 0.5);
  return min(min(cap, cup), minus);
}

vec3 gradSDF(vec3 p){
  float eps = 0.0001;
  return normalize(vec3(
    sceneSDF(p + vec3(eps, 0.0, 0.0)) - sceneSDF(p + vec3(-eps, 0.0, 0.0)),
    sceneSDF(p + vec3(0.0, eps, 0.0)) - sceneSDF(p + vec3(0.0, - eps, 0.0)),
    sceneSDF(p + vec3(0.0, 0.0, eps)) - sceneSDF(p + vec3(0.0, 0.0, - eps))
  ));
}

void main(){
  vec2 p = (gl_FragCoord.xy * 2.0 - u_resolution) / min(u_resolution.x, u_resolution.y);

  vec3 cPos = vec3(0.0, 0.0, 2.0);
  vec3 cDir = vec3(0.0, 0.0, - 1.0);
  vec3 cUp = vec3(0.0, 1.0, 0.0);
  vec3 cSide = cross(cDir, cUp);
  float targetDepth = 1.0;

  vec3 lDir = vec3(0.0, 0.0, 1.0);

  vec3 ray = cSide * p.x + cUp * p.y + cDir * targetDepth;
  vec3 rPos = cPos + ray;
  ray = normalize(ray);
  fragColor.rgb = vec3(0.0);
  for(int i = 0; i < 50; i ++ ){
    if (sceneSDF(rPos) > 0.001){
      rPos += sceneSDF(rPos) * ray;
    } else {
      float amb = 0.1;
      float diff = 0.9 * max(dot(normalize(lDir), gradSDF(rPos)), 0.0);
      vec3 col = vec3(1.0);
      fragColor.rgb = col * (diff + amb);
      break;
    }
  }
  fragColor.a = 1.0;
}