class RainEffect {
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constructor(viewer, options) {
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if (!viewer) throw new Error("no viewer object!");
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options = options || {};
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//倾斜角度，负数向右，正数向左
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this.tiltAngle = Cesium.defaultValue(options.tiltAngle, -0.6);
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this.rainSize = Cesium.defaultValue(options.rainSize, 0.3);
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this.rainSpeed = Cesium.defaultValue(options.rainSpeed, 60.0);
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this.rainDensity = Cesium.defaultValue(options.rainDensity, 30.0);
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this.color = Cesium.defaultValue(options.color, new Cesium.Color(0.6, 0.7, 0.8, 1.0));
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this.viewer = viewer;
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this.init();
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}
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init() {
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this.rainStage = new Cesium.PostProcessStage({
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name: "czm_rain",
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fragmentShader: this.rain(),
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uniforms: {
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tiltAngle: () => {
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return this.tiltAngle;
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},
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rainSize: () => {
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return this.rainSize;
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},
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rainColor: () => {
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return this.color;
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},
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rainSpeed: () => {
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return this.rainSpeed;
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},
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rainDensity: () => {
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return this.rainDensity;
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},
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},
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});
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this.viewer.scene.postProcessStages.add(this.rainStage);
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}
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destroy() {
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if (!this.viewer || !this.rainStage) return;
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this.viewer.scene.postProcessStages.remove(this.rainStage);
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const isDestroyed = this.rainStage.isDestroyed();
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// 先检查是否被销毁过，如果已经被销毁过再调用destroy会报错
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if (!isDestroyed) {
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this.rainStage.destroy();
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}
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delete this.tiltAngle;
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delete this.rainSize;
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delete this.rainSpeed;
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delete this.rainDensity;
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}
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show(visible) {
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this.rainStage.enabled = visible;
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}
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rain() {
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return "uniform sampler2D colorTexture;\n\
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in vec2 v_textureCoordinates;\n\
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uniform float tiltAngle;\n\
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uniform vec4 rainColor;\n\
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uniform float rainSize;\n\
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uniform float rainSpeed;\n\
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uniform float rainDensity;\n\
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float hash(float x) {\n\
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return fract(sin(x * 133.3) * 13.13);\n\
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}\n\
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out vec4 fragColor;\n\
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void main(void) {\n\
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float time = czm_frameNumber * (rainSpeed / 10000.0);\n\
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vec2 resolution = czm_viewport.zw;\n\
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vec2 uv = (gl_FragCoord.xy * 2. - resolution.xy) / min(resolution.x, resolution.y);\n\
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vec3 c = rainColor.rgb;\n\
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float a = tiltAngle;\n\
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float si = sin(a), co = cos(a);\n\
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uv *= mat2(co, -si, si, co);\n\
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uv *= length(uv + vec2(0, 4.9)) / (rainSize * 3.0 + 0.1) + 0.5;\n\
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// 限制最大密度值，使用对数函数来压缩高密度范围\n\
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float cappedDensity = min(rainDensity, 30.0 + (rainDensity - 30.0) * 0.1);\n\
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float densityScale = pow(cappedDensity / 200.0, 0.4); // 使用0.4次幂进一步压缩\n\
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// 减少基础雨滴数量\n\
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float v = 1. - sin(hash(floor(uv.x * (25.0 + densityScale * 50.0))) * 2.);\n\
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// 使用更严格的阈值函数，让高密度时增加更少的雨\n\
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float densityThreshold = 0.96 - (0.15 * log(1.0 + cappedDensity / 50.0));\n\
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float b = clamp(abs(sin(20. * time * v + uv.y * (5. / (2. + v)))) - densityThreshold, 0., 1.) * 20.;\n\
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// 计算雨滴颜色\n\
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vec3 finalColor = rainColor.rgb * v * b;\n\
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// 调整混合系数\n\
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float mixFactor = min(b * 0.05, 0.5);\n\
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fragColor = mix(texture(colorTexture, v_textureCoordinates), vec4(finalColor, 1), mixFactor);\n\
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}\n\
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";
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}
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}
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export default RainEffect;
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