dc-sdk/modules/material/shader/weather/RainShader.glsl

uniform sampler2D colorTexture;
varying vec2 v_textureCoordinates;
uniform float speed;

float hash(float x){
  return fract(sin(x*23.3)*13.13);
}

void main(){
  float time = czm_frameNumber * speed / 1000.0;
  vec2 resolution = czm_viewport.zw;
  vec2 uv=(gl_FragCoord.xy*2.-resolution.xy)/min(resolution.x,resolution.y);
  vec3 c=vec3(.1,.2,.3);
  float a=-.3;
  float si=sin(a),co=cos(a);
  uv*=mat2(co,-si,si,co);
  uv*=length(uv+vec2(0,4.9))*.3+1.;
  float v=1.-sin(hash(floor(uv.x*100.))*2.);
  float b=clamp(abs(sin(20.*time*v+uv.y*(5./(2.+v))))-.95,0.,1.)*10.;
  c*=v*b;
  gl_FragColor = mix(texture2D(colorTexture, v_textureCoordinates), vec4(c,1), 0.5);
}