//This file is automatically rebuilt by the Cesium build process. export default "uniform vec3 u_radiiAndDynamicAtmosphereColor;\n\ \n\ uniform float u_atmosphereLightIntensity;\n\ uniform float u_atmosphereRayleighScaleHeight;\n\ uniform float u_atmosphereMieScaleHeight;\n\ uniform float u_atmosphereMieAnisotropy;\n\ uniform vec3 u_atmosphereRayleighCoefficient;\n\ uniform vec3 u_atmosphereMieCoefficient;\n\ \n\ const float ATMOSPHERE_THICKNESS = 111e3; // The thickness of the atmosphere in meters.\n\ const int PRIMARY_STEPS = 16; // Number of times the ray from the camera to the world position (primary ray) is sampled.\n\ const int LIGHT_STEPS = 4; // Number of times the light is sampled from the light source's intersection with the atmosphere to a sample position on the primary ray.\n\ \n\ /**\n\ * This function computes the colors contributed by Rayliegh and Mie scattering on a given ray, as well as\n\ * the transmittance value for the ray.\n\ *\n\ * @param {czm_ray} primaryRay The ray from the camera to the position.\n\ * @param {float} primaryRayLength The length of the primary ray.\n\ * @param {vec3} lightDirection The direction of the light to calculate the scattering from.\n\ * @param {vec3} rayleighColor The variable the Rayleigh scattering will be written to.\n\ * @param {vec3} mieColor The variable the Mie scattering will be written to.\n\ * @param {float} opacity The variable the transmittance will be written to.\n\ * @glslFunction\n\ */\n\ void computeScattering(\n\ czm_ray primaryRay,\n\ float primaryRayLength,\n\ vec3 lightDirection,\n\ float atmosphereInnerRadius,\n\ out vec3 rayleighColor,\n\ out vec3 mieColor,\n\ out float opacity\n\ ) {\n\ \n\ // Initialize the default scattering amounts to 0.\n\ rayleighColor = vec3(0.0);\n\ mieColor = vec3(0.0);\n\ opacity = 0.0;\n\ \n\ float atmosphereOuterRadius = atmosphereInnerRadius + ATMOSPHERE_THICKNESS;\n\ \n\ vec3 origin = vec3(0.0);\n\ \n\ // Calculate intersection from the camera to the outer ring of the atmosphere.\n\ czm_raySegment primaryRayAtmosphereIntersect = czm_raySphereIntersectionInterval(primaryRay, origin, atmosphereOuterRadius);\n\ \n\ // Return empty colors if no intersection with the atmosphere geometry.\n\ if (primaryRayAtmosphereIntersect == czm_emptyRaySegment) {\n\ return;\n\ }\n\ \n\ // The ray should start from the first intersection with the outer atmopshere, or from the camera position, if it is inside the atmosphere.\n\ primaryRayAtmosphereIntersect.start = max(primaryRayAtmosphereIntersect.start, 0.0);\n\ // The ray should end at the exit from the atmosphere or at the distance to the vertex, whichever is smaller.\n\ primaryRayAtmosphereIntersect.stop = min(primaryRayAtmosphereIntersect.stop, length(primaryRayLength));\n\ \n\ // Setup for sampling positions along the ray - starting from the intersection with the outer ring of the atmosphere.\n\ float rayStepLength = (primaryRayAtmosphereIntersect.stop - primaryRayAtmosphereIntersect.start) / float(PRIMARY_STEPS);\n\ float rayPositionLength = primaryRayAtmosphereIntersect.start;\n\ \n\ vec3 rayleighAccumulation = vec3(0.0);\n\ vec3 mieAccumulation = vec3(0.0);\n\ vec2 opticalDepth = vec2(0.0);\n\ vec2 heightScale = vec2(u_atmosphereRayleighScaleHeight, u_atmosphereMieScaleHeight);\n\ \n\ // Sample positions on the primary ray.\n\ for (int i = 0; i < PRIMARY_STEPS; i++) {\n\ // Calculate sample position along viewpoint ray.\n\ vec3 samplePosition = primaryRay.origin + primaryRay.direction * (rayPositionLength + rayStepLength);\n\ \n\ // Calculate height of sample position above ellipsoid.\n\ float sampleHeight = length(samplePosition) - atmosphereInnerRadius;\n\ \n\ // Calculate and accumulate density of particles at the sample position.\n\ vec2 sampleDensity = exp(-sampleHeight / heightScale) * rayStepLength;\n\ opticalDepth += sampleDensity;\n\ \n\ // Generate ray from the sample position segment to the light source, up to the outer ring of the atmosphere.\n\ czm_ray lightRay = czm_ray(samplePosition, lightDirection);\n\ czm_raySegment lightRayAtmosphereIntersect = czm_raySphereIntersectionInterval(lightRay, origin, atmosphereOuterRadius);\n\ \n\ float lightStepLength = lightRayAtmosphereIntersect.stop / float(LIGHT_STEPS);\n\ float lightPositionLength = 0.0;\n\ \n\ vec2 lightOpticalDepth = vec2(0.0);\n\ \n\ // Sample positions along the light ray, to accumulate incidence of light on the latest sample segment.\n\ for (int j = 0; j < LIGHT_STEPS; j++) {\n\ \n\ // Calculate sample position along light ray.\n\ vec3 lightPosition = samplePosition + lightDirection * (lightPositionLength + lightStepLength * 0.5);\n\ \n\ // Calculate height of the light sample position above ellipsoid.\n\ float lightHeight = length(lightPosition) - atmosphereInnerRadius;\n\ \n\ // Calculate density of photons at the light sample position.\n\ lightOpticalDepth += exp(-lightHeight / heightScale) * lightStepLength;\n\ \n\ // Increment distance on light ray.\n\ lightPositionLength += lightStepLength;\n\ }\n\ \n\ // Compute attenuation via the primary ray and the light ray.\n\ vec3 attenuation = exp(-((u_atmosphereMieCoefficient * (opticalDepth.y + lightOpticalDepth.y)) + (u_atmosphereRayleighCoefficient * (opticalDepth.x + lightOpticalDepth.x))));\n\ \n\ // Accumulate the scattering.\n\ rayleighAccumulation += sampleDensity.x * attenuation;\n\ mieAccumulation += sampleDensity.y * attenuation;\n\ \n\ // Increment distance on primary ray.\n\ rayPositionLength += rayStepLength;\n\ }\n\ \n\ // Compute the scattering amount.\n\ rayleighColor = u_atmosphereRayleighCoefficient * rayleighAccumulation;\n\ mieColor = u_atmosphereMieCoefficient * mieAccumulation;\n\ \n\ // Compute the transmittance i.e. how much light is passing through the atmosphere.\n\ opacity = length(exp(-((u_atmosphereMieCoefficient * opticalDepth.y) + (u_atmosphereRayleighCoefficient * opticalDepth.x))));\n\ }\n\ \n\ vec4 computeAtmosphereColor(\n\ vec3 positionWC,\n\ vec3 lightDirection,\n\ vec3 rayleighColor,\n\ vec3 mieColor,\n\ float opacity\n\ ) {\n\ // Setup the primary ray: from the camera position to the vertex position.\n\ vec3 cameraToPositionWC = positionWC - czm_viewerPositionWC;\n\ vec3 cameraToPositionWCDirection = normalize(cameraToPositionWC);\n\ \n\ float cosAngle = dot(cameraToPositionWCDirection, lightDirection);\n\ float cosAngleSq = cosAngle * cosAngle;\n\ \n\ float G = u_atmosphereMieAnisotropy;\n\ float GSq = G * G;\n\ \n\ // The Rayleigh phase function.\n\ float rayleighPhase = 3.0 / (50.2654824574) * (1.0 + cosAngleSq);\n\ // The Mie phase function.\n\ float miePhase = 3.0 / (25.1327412287) * ((1.0 - GSq) * (cosAngleSq + 1.0)) / (pow(1.0 + GSq - 2.0 * cosAngle * G, 1.5) * (2.0 + GSq));\n\ \n\ // The final color is generated by combining the effects of the Rayleigh and Mie scattering.\n\ vec3 rayleigh = rayleighPhase * rayleighColor;\n\ vec3 mie = miePhase * mieColor;\n\ \n\ vec3 color = (rayleigh + mie) * u_atmosphereLightIntensity;\n\ \n\ return vec4(color, opacity);\n\ }\n\ ";