Cesium-Examples/examples/cesiumEx/weatherEffects.js

/***
 * @class DEUGlobe.Scene.sceneEffects.weatherEffects
 * @category  场景
 * @classdesc 场景特效-天气特效
 * @param {Object} viewer -  Cesium.viewer。
 * @param {Object} options - 参数。
 * @param {String} options.name - 天气特效名称。
 * @param {String} options.type - 天气特效类型. (snow：雪 ， rain：雨，fog：雾)。
*/
 class weatherEffects{
    constructor(viewer,options){
      this.viewer = viewer;
      var opt = options || {};
      this.name = opt.name;
      this.type = opt.type;
      let stage = this.getStage(), 
      fs = null;
      if(stage == null){
          switch(this.type){
            case "snow":
              fs = this.fs_snow();
            break;
            case "rain":
              fs = this.fs_rain();
            break;
            case "fog":
                fs = this.fs_fog();
            break;
          }
      }
      stage = new Cesium.PostProcessStage({
            name : this.name,
            fragmentShader:fs,
            uniforms : {
              color: Cesium.Color.fromAlpha(Cesium.Color.BLACK, parseFloat(1)),
            }
      });
      viewer.scene.postProcessStages.add(stage);
    }
    removePostProcessStage(){
     let stage =  this.getStage();
      if(stage){
        this.viewer.scene.postProcessStages.remove(stage);
      }
    }
    getStage(){
      let stage = null,
          stages =  this.viewer.scene.postProcessStages;
      for(let i = 0;i<stages._stages.length;i++){
        let tmp = stages.get(i);
        if(tmp != undefined && tmp.name == this.name){
          stage = tmp;
          break;
        }
      }
      return stage;
    }
    fs_snow(){
      return 'uniform sampler2D colorTexture;\n'
        + 'varying vec2 v_textureCoordinates;\n'
        + 'float snow(vec2 uv,float scale)\n'
        + '{\n'
        + '    float time = czm_frameNumber / 60.0;\n'
        + '    float w=smoothstep(1.,0.,-uv.y*(scale/10.));if(w<.1)return 0.;\n'
        + '    uv+=time/scale;uv.y+=time*2./scale;uv.x+=sin(uv.y+time*.5)/scale;\n'
        + '    uv*=scale;vec2 s=floor(uv),f=fract(uv),p;float k=3.,d;\n'
        + '    p=.5+.35*sin(11.*fract(sin((s+p+scale)*mat2(7,3,6,5))*5.))-f;d=length(p);k=min(d,k);\n'
        + '    k=smoothstep(0.,k,sin(f.x+f.y)*0.01);\n'
        + '    return k*w;\n'
        + '}\n'
        + 'void main(void){\n'
        + '     vec2 resolution = czm_viewport.zw;\n'
        + '     vec2 uv=(gl_FragCoord.xy*2.-resolution.xy)/min(resolution.x,resolution.y);\n'
        + '     vec3 finalColor=vec3(0);\n'
        + '     float c = 0.0;\n'
        + '     c+=snow(uv,30.)*.0;\n'
        + '     c+=snow(uv,20.)*.0;\n'
        + '     c+=snow(uv,15.)*.0;\n'
        + '     c+=snow(uv,10.);\n'
        + '     c+=snow(uv,8.);\n'
        + '     c+=snow(uv,6.);\n'
        + '     c+=snow(uv,5.);\n'
        + '     finalColor=(vec3(c));\n' 
        + '     gl_FragColor = mix(texture2D(colorTexture, v_textureCoordinates), vec4(finalColor,1), 0.5);\n' 
        + '}';
    }
    fs_rain(){
      return 'uniform sampler2D colorTexture;\n'
            + 'varying vec2 v_textureCoordinates;\n'
        + '	float hash(float x){\n'
        + '	     return fract(sin(x*133.3)*13.13);\n'
        + '	 }\n' 
        + '	void main(void){\n'
        + '	     float time = czm_frameNumber / 60.0;\n'
        + '	     vec2 resolution = czm_viewport.zw; \n'
        + '	     vec2 uv=(gl_FragCoord.xy*2.-resolution.xy)/min(resolution.x,resolution.y);\n'
        + '	     vec3 c=vec3(.6,.7,.8); \n'
        + '	     float a=-.4;\n'
        + '	     float si=sin(a),co=cos(a);\n'
        + '	     uv*=mat2(co,-si,si,co);\n'
        + '	     uv*=length(uv+vec2(0,4.9))*.3+1.;\n'
        + '	     float v=1.-sin(hash(floor(uv.x*100.))*2.);\n'
        + '	     float b=clamp(abs(sin(20.*time*v+uv.y*(5./(2.+v))))-.95,0.,1.)*20.;\n'
        + '	     c*=v*b; \n'
        + '	     gl_FragColor = mix(texture2D(colorTexture, v_textureCoordinates), vec4(c,1), 0.5); \n'
        + '	}';
    }
    fs_fog(){
      return 'uniform sampler2D colorTexture;\n'
          +'  uniform sampler2D depthTexture;\n' 
          +'  varying vec2 v_textureCoordinates;\n'
          +'  void main(void)\n'
          +'  {\n'
          +'      vec4 origcolor=texture2D(colorTexture, v_textureCoordinates);\n'
          +'      vec4 fogcolor=vec4(0.8,0.8,0.8,0.5);\n'
          +'      float depth = czm_readDepth(depthTexture, v_textureCoordinates);\n'
          +'      vec4 depthcolor=texture2D(depthTexture, v_textureCoordinates);\n'
          +'      float f=(depthcolor.r-0.22)/0.2;\n'
          +'      if(f<0.0) f=0.0;\n'
          +'      else if(f>1.0) f=1.0;\n'
          +'      gl_FragColor = mix(origcolor,fogcolor,0.8);\n'
          +'   }';
    }
}