water_shader.frag

#define PROCESSING_TEXTURE_SHADER

uniform sampler2D texture;
uniform vec2 texOffset;
varying vec4 vertColor;
varying vec4 vertTexCoord;
uniform float level;

float map(float a,float amin,float amax,float bmin,float bmax) {
  return (a-amin)/(amax-amin) * (bmax-bmin) + bmin;
}

void main(void) {
  vec2 tc0 = vertTexCoord.st + vec2(-texOffset.s, -texOffset.t);
  vec4 col0 = texture2D(texture, tc0);
  vec4 color;

  vec4 dark_blue = vec4(0.0,0.0,0.5,1.0);
  vec4 light_blue = vec4(0.,0.658,1.0,1.0);

  vec4 dark_green = vec4(0.0,0.5,0.0,1.0);
  vec4 light_green = vec4(0.0,1.0,0.0,1.0);

  vec4 black = vec4(0.0,0.0,0.0,1.0);

  if (col0.r<level) {
    color = mix(dark_blue,light_blue,col0.r/level);
  }
  else {
    float p = map(col0.r,level,1.0,0.0,1.0);
    color = mix(dark_green,black,p);
  }

  gl_FragColor = color;
}