text: // Copyright 2017 The Fuchsia Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  // This file contains GLSL source code strings from the shadertoy.com website.
  // The copyright of this code is owned by the respective authors, as described
  // in each GLSL program below.
  
  #include "garnet/examples/ui/shadertoy/client/glsl_strings.h"
  
  namespace shadertoy_client {
  
  constexpr char kSeascapeSrc[] = R"GLSL(
  /*
   * "Seascape" by Alexander Alekseev aka TDM - 2014
   * License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
   * Contact: tdmaav@gmail.com
   */
  
  const int NUM_STEPS = 8;
  const float PI	 	= 3.141592;
  const float EPSILON	= 1e-3;
  #define EPSILON_NRM (0.1 / iResolution.x)
  
  // sea
  const int ITER_GEOMETRY = 3;
  const int ITER_FRAGMENT = 5;
  const float SEA_HEIGHT = 0.6;
  const float SEA_CHOPPY = 4.0;
  const float SEA_SPEED = 0.8;
  const float SEA_FREQ = 0.16;
  const vec3 SEA_BASE = vec3(0.1,0.19,0.22);
  const vec3 SEA_WATER_COLOR = vec3(0.8,0.9,0.6);
  #define SEA_TIME (1.0 + iGlobalTime * SEA_SPEED)
  const mat2 octave_m = mat2(1.6,1.2,-1.2,1.6);
  
  // math
  mat3 fromEuler(vec3 ang) {
      vec2 a1 = vec2(sin(ang.x),cos(ang.x));
      vec2 a2 = vec2(sin(ang.y),cos(ang.y));
      vec2 a3 = vec2(sin(ang.z),cos(ang.z));
      mat3 m;
      m[0] = vec3(a1.y*a3.y+a1.x*a2.x*a3.x,a1.y*a2.x*a3.x+a3.y*a1.x,-a2.y*a3.x);
      m[1] = vec3(-a2.y*a1.x,a1.y*a2.y,a2.x);
      m[2] = vec3(a3.y*a1.x*a2.x+a1.y*a3.x,a1.x*a3.x-a1.y*a3.y*a2.x,a2.y*a3.y);
      return m;
  }
  float hash( vec2 p ) {
      float h = dot(p,vec2(127.1,311.7));
      return fract(sin(h)*43758.5453123);
  }
  float noise( in vec2 p ) {
      vec2 i = floor( p );
      vec2 f = fract( p );
      vec2 u = f*f*(3.0-2.0*f);
      return -1.0 + 2.0 * mix( mix( hash( i + vec2(0.0,0.0) ),
                                    hash( i + vec2(1.0,0.0) ), u.x),
                               mix( hash( i + vec2(0.0,1.0) ),
                                    hash( i + vec2(1.0,1.0) ), u.x), u.y);
  }
  
  // lighting
  float diffuse(vec3 n,vec3 l,float p) {
      return pow(dot(n,l) * 0.4 + 0.6,p);
  }
  float specular(vec3 n,vec3 l,vec3 e,float s) {
      float nrm = (s + 8.0) / (PI * 8.0);
      return pow(max(dot(reflect(e,n),l),0.0),s) * nrm;
  }
  
  // sky
  vec3 getSkyColor(vec3 e) {
      e.y = max(e.y,0.0);
      return vec3(pow(1.0-e.y,2.0), 1.0-e.y, 0.6+(1.0-e.y)*0.4);
  }
  
  // sea
  float sea_octave(vec2 uv, float choppy) {
      uv += noise(uv);
      vec2 wv = 1.0-abs(sin(uv));
      vec2 swv = abs(cos(uv));
      wv = mix(wv,swv,wv);
      return pow(1.0-pow(wv.x * wv.y,0.65),choppy);
  }
  
  float map(vec3 p) {
      float freq = SEA_FREQ;
      float amp = SEA_HEIGHT;
      float choppy = SEA_CHOPPY;
      vec2 uv = p.xz; uv.x *= 0.75;
  
      float d, h = 0.0;
      for(int i = 0; i < ITER_GEOMETRY; i++) {
          d = sea_octave((uv+SEA_TIME)*freq,choppy);
          d += sea_octave((uv-SEA_TIME)*freq,choppy);
          h += d * amp;
          uv *= octave_m; freq *= 1.9; amp *= 0.22;
          choppy = mix(choppy,1.0,0.2);
      }
      return p.y - h;
  }
  
  float map_detailed(vec3 p) {
      float freq = SEA_FREQ;
      float amp = SEA_HEIGHT;
      float choppy = SEA_CHOPPY;
      vec2 uv = p.xz; uv.x *= 0.75;
  
      float d, h = 0.0;
      for(int i = 0; i < ITER_FRAGMENT; i++) {
          d = sea_octave((uv+SEA_TIME)*freq,choppy);
          d += sea_octave((uv-SEA_TIME)*freq,choppy);
          h += d * amp;
          uv *= octave_m; freq *= 1.9; amp *= 0.22;
          choppy = mix(choppy,1.0,0.2);
      }
      return p.y - h;
  }
  
  vec3 getSeaColor(vec3 p, vec3 n, vec3 l, vec3 eye, vec3 dist) {
      float fresnel = clamp(1.0 - dot(n,-eye), 0.0, 1.0);
      fresnel = pow(fresnel,3.0) * 0.65;
  
      vec3 reflected = getSkyColor(reflect(eye,n));
      vec3 refracted = SEA_BASE + diffuse(n,l,80.0) * SEA_WATER_COLOR * 0.12;
  
      vec3 color = mix(refracted,reflected,fresnel);
  
      float atten = max(1.0 - dot(dist,dist) * 0.001, 0.0);
      color += SEA_WATER_COLOR * (p.y - SEA_HEIGHT) * 0.18 * atten;
  
      color += vec3(specular(n,l,eye,60.0));
  
      return color;
  }
  
  // tracing
  vec3 getNormal(vec3 p, float eps) {
      vec3 n;
      n.y = map_detailed(p);
      n.x = map_detailed(vec3(p.x+eps,p.y,p.z)) - n.y;
      n.z = map_detailed(vec3(p.x,p.y,p.z+eps)) - n.y;
      n.y = eps;
      return normalize(n);
  }
  
  float heightMapTracing(vec3 ori, vec3 dir, out vec3 p) {
      float tm = 0.0;
      float tx = 1000.0;
      float hx = map(ori + dir * tx);
      if(hx > 0.0) return tx;
      float hm = map(ori + dir * tm);
      float tmid = 0.0;
      for(int i = 0; i < NUM_STEPS; i++) {
          tmid = mix(tm,tx, hm/(hm-hx));
          p = ori + dir * tmid;
          float hmid = map(p);
          if(hmid < 0.0) {
              tx = tmid;
              hx = hmid;
          } else {
              tm = tmid;
              hm = hmid;
          }
      }
      return tmid;
  }
  
  // main
  void mainImage( out vec4 fragColor, in vec2 fragCoord ) {
      vec2 uv = fragCoord.xy / iResolution.xy;
      uv = uv * 2.0 - 1.0;
      uv.x *= iResolution.x / iResolution.y;
      float time = iGlobalTime * 0.3 + iMouse.x*0.01;
  
      // ray
      vec3 ang = vec3(sin(time*3.0)*0.1,sin(time)*0.2+0.3,time);
      vec3 ori = vec3(0.0,3.5,time*5.0);
      vec3 dir = normalize(vec3(uv.xy,-2.0)); dir.z += length(uv) * 0.15;
      dir = normalize(dir) * fromEuler(ang);
  
      // tracing
      vec3 p;
      heightMapTracing(ori,dir,p);
      vec3 dist = p - ori;
      vec3 n = getNormal(p, dot(dist,dist) * EPSILON_NRM);
      vec3 light = normalize(vec3(0.0,1.0,0.8));
  
      // color
      vec3 color = mix(
          getSkyColor(dir),
          getSeaColor(p,n,light,dir,dist),
      pow(smoothstep(0.0,-0.05,dir.y),0.3));
  
      // post
      fragColor = vec4(pow(color,vec3(0.75)), 1.0);
  }
  )GLSL";
  
  constexpr char kMouseInputSrc[] = R"GLSL(
  // Created by inigo quilez - iq/2013
  // License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
  
  float distanceToSegment( vec2 a, vec2 b, vec2 p )
  {
      vec2 pa = p - a, ba = b - a;
      float h = clamp( dot(pa,ba)/dot(ba,ba), 0.0, 1.0 );
      return length( pa - ba*h );
  }
  
  void mainImage( out vec4 fragColor, in vec2 fragCoord )
  {
      vec2 p = fragCoord.xy / iResolution.xx;
      vec4 m = iMouse / iResolution.xxxx;
  
      vec3 col = vec3(0.0);
  
      if( m.z>0.0 )
      {
          float d = distanceToSegment( m.xy, m.zw, p );
          col = mix( col, vec3(1.0,1.0,0.0), 1.0-smoothstep(.004,0.008, d) );
      }
  
      col = mix( col, vec3(1.0,0.0,0.0), 1.0-smoothstep(0.03,0.035, length(p-m.xy)) );
      col = mix( col, vec3(0.0,0.0,1.0), 1.0-smoothstep(0.03,0.035, length(p-abs(m.zw))) );
  
      fragColor = vec4( col, 1.0 );
  }
  )GLSL";
  
  std::string GetSeascapeSourceCode() { return kSeascapeSrc; }
  
  std::string GetMouseInputSourceCode() { return kMouseInputSrc; }
  
  }  // namespace shadertoy_client
  