2025-03-11 08:25:45 +00:00
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<!--********************************************************************
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* by jiawanlong
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*********************************************************************-->
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<!DOCTYPE html>
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<html>
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<head>
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<meta charset="UTF-8" />
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2025-03-19 03:00:22 +00:00
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<link rel="stylesheet" href="./../../libs/cesium/Cesium1.98/Widgets/widgets.css">
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<script type="text/javascript" src="./../../libs/cesium/Cesium1.98/Cesium.js"></script>
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2025-03-11 08:25:45 +00:00
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</head>
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<body style="margin: 0; overflow: hidden; background: #fff; width: 100%; height: 100%; position: absolute; top: 0">
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<div id="map" style="margin: 0 auto; width: 100%; height: 100%"></div>
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<script type="text/javascript">
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Cesium.Ion.defaultAccessToken = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJqdGkiOiI3ZjQ5ZGUzNC1jNWYwLTQ1ZTMtYmNjYS05YTY4ZTVmN2I2MDkiLCJpZCI6MTE3MTM4LCJpYXQiOjE2NzY0NDUyODB9.ZaNSBIfc1sGLhQd_xqhiSsc0yr8oS0wt1hAo9gbke6M'
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const viewer = new Cesium.Viewer('map', {});
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// 开启帧率
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viewer.scene.debugShowFramesPerSecond = true;
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// 深度监测
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viewer.scene.globe.depthTestAgainstTerrain = true;
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// 清除默认地形
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viewer.scene.terrainProvider = new Cesium.EllipsoidTerrainProvider({});
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// 加载火星地形
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viewer.terrainProvider = new Cesium.CesiumTerrainProvider({
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url: 'http://data.mars3d.cn/terrain'
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})
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const fs = `
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uniform sampler2D colorTexture; // 颜色纹理
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uniform sampler2D depthTexture; // 深度纹理
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in vec2 v_textureCoordinates; // 纹理坐标
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uniform float u_earthRadiusOnCamera;
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uniform float u_cameraHeight;
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uniform float u_fogHeight;
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uniform vec3 u_fogColor;
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uniform float u_globalDensity;
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// 通过深度纹理与纹理坐标得到世界坐标
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vec4 getWorldCoordinate(sampler2D depthTexture, vec2 texCoords) {
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float depthOrLogDepth = czm_unpackDepth(texture(depthTexture, texCoords));
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vec4 eyeCoordinate = czm_windowToEyeCoordinates(gl_FragCoord.xy, depthOrLogDepth);
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eyeCoordinate = eyeCoordinate / eyeCoordinate.w;
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vec4 worldCoordinate = czm_inverseView * eyeCoordinate;
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worldCoordinate = worldCoordinate / worldCoordinate.w;
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return worldCoordinate;
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}
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// 计算粗略的高程，依赖js传递的相机位置处的地球高程u_earthRadiusOnCamera。好处是计算量非常低
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float getRoughHeight(vec4 worldCoordinate) {
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float disToCenter = length(vec3(worldCoordinate));
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return disToCenter - u_earthRadiusOnCamera;
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}
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// 得到a向量在b向量的投影长度，如果同向结果为正，异向结果为复
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float projectVector(vec3 a, vec3 b) {
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float scale = dot(a, b) / dot(b, b);
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float k = scale / abs(scale);
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return k * length(scale * b);
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}
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// 线性浓度积分高度雾
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float linearHeightFog(vec3 positionToCamera, float cameraHeight, float pixelHeight, float fogMaxHeight) {
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float globalDensity = u_globalDensity / 10.0;
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vec3 up = -1.0 * normalize(czm_viewerPositionWC);
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float vh = projectVector(normalize(positionToCamera), up);
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// 让相机沿着视线方向移动 雾气产生距离 的距离
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float s = step(100.0, length(positionToCamera));
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vec3 sub = mix(positionToCamera, normalize(positionToCamera) * 100.0, s);
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positionToCamera -= sub;
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cameraHeight = mix(pixelHeight, cameraHeight - 100.0 * vh, s);
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float b = mix(cameraHeight, fogMaxHeight, step(fogMaxHeight, cameraHeight));
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float a = mix(pixelHeight, fogMaxHeight, step(fogMaxHeight, pixelHeight));
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float fog = (b - a) - 0.5 * (pow(b, 2.0) - pow(a, 2.0)) / fogMaxHeight;
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fog = globalDensity * fog / vh;
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if(abs(vh) <= 0.01 && cameraHeight < fogMaxHeight) {
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float disToCamera = length(positionToCamera);
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fog = globalDensity * (1.0 - cameraHeight / fogMaxHeight) * disToCamera;
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}
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fog = mix(0.0, 1.0, fog / (fog + 1.0));
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return fog;
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}
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void main(void) {
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vec4 color = texture(colorTexture, v_textureCoordinates);
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vec4 positionWC = getWorldCoordinate(depthTexture, v_textureCoordinates);
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float pixelHeight = getRoughHeight(positionWC);
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vec3 positionToCamera = vec3(vec3(positionWC) - czm_viewerPositionWC);
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float fog = linearHeightFog(positionToCamera, u_cameraHeight, pixelHeight, u_fogHeight);
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out_FragColor = mix(color, vec4(u_fogColor, 1.0), fog);
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}`
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const customPostProcessStage = new Cesium.PostProcessStage({
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fragmentShader: fs,
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uniforms: {
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u_earthRadiusOnCamera: () => Cesium.Cartesian3.magnitude(viewer.camera.positionWC) - viewer.camera.positionCartographic.height,
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u_cameraHeight: () => viewer.camera.positionCartographic.height,
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u_fogColor: () => new Cesium.Color(0.8, 0.82, 0.84),
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u_fogHeight: () => 1000,
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u_globalDensity: () => 0.6,
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}
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})
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viewer.scene.postProcessStages.add(customPostProcessStage)
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viewer.camera.setView({
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destination:new Cesium.Cartesian3(-1386705.7605894802,5226754.975571179,3375582.2076837276),
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orientation: {
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heading:3.968066845543675, // east, default value is 0.0 (north)
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pitch: -0.300780994602595, // default value (looking down)
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roll: 0.00007913394522685024 // default value
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}
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});
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</script>
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</body>
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</html>
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