uniform sampler2D colorTexture;//输入的场景渲染照片
varying vec2 v_textureCoordinates;

float hash(float x){
    return fract(sin(x*133.3)*13.13);
}

void main(void){

    float time = czm_frameNumber / 500.0;
    vec2 resolution = czm_viewport.zw;

    vec2 uv=(gl_FragCoord.xy*2.-resolution.xy)/min(resolution.x,resolution.y);
    vec3 c=vec3(.6,.7,.8);

    float a=-.4;
    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.)*20.;
    c*=v*b; //屏幕上雨的颜色

    gl_FragColor = mix(texture2D(colorTexture, v_textureCoordinates), vec4(c,1), 0.5); //将雨和三维场景融合
}