上一篇写了一个下雨的效果，本文是一个下雪的效果
- 下雪效果的类代码：
class SnowEffect {
constructor(viewer, options) {
if (!viewer) throw new Error('no viewer object!');
options = options || {};
this.snowSize = Cesium.defaultValue(options.snowSize, 0.02); //最好小于0.02
this.snowSpeed = Cesium.defaultValue(options.snowSpeed, 60.0);
this.viewer = viewer;
this.init();
}
init() {
this.snowStage = new Cesium.PostProcessStage({
name: 'czm_snow',
fragmentShader: this.snow(),
uniforms: {
snowSize: () => {
return this.snowSize;
},
snowSpeed: () => {
return this.snowSpeed;
}
}
});
this.viewer.scene.postProcessStages.add(this.snowStage);
}
destroy() {
if (!this.viewer || !this.snowStage) return;
this.viewer.scene.postProcessStages.remove(this.snowStage);
this.snowStage.destroy();
delete this.snowSize;
delete this.snowSpeed;
}
show(visible) {
this.snowStage.enabled = visible;
}
snow() {
return "uniform sampler2D colorTexture;\n\
varying vec2 v_textureCoordinates;\n\
uniform float snowSpeed;\n\
uniform float snowSize;\n\
float snow(vec2 uv,float scale)\n\
{\n\
float time=czm_frameNumber/snowSpeed;\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)*snowSize);\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=smoothstep(1.,0.3,clamp(uv.y*.3+.8,0.,.75));\n\
float c=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),.5);\n\
}\n\
";
}
}
Cesium.SnowEffect = SnowEffect;
- 页面使用方式
引入上面的js即可
new Cesium.SnowEffect(viewer, {
snowSize: 0.02, //雪大小 ，默认可不写
snowSpeed: 60.0 //雪速，默认可不写
});
-
效果图
cesium_snow.gif
