/**
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* @license
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* Copyright (c) 2000-2005, Sean O'Neil (s_p_oneil@hotmail.com)
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* * Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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* * Neither the name of the project nor the names of its contributors may be
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* used to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Modifications made by Analytical Graphics, Inc.
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*/
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// Code: http://sponeil.net/
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// GPU Gems 2 Article: https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_chapter16.html
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attribute vec4 position;
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uniform vec4 u_cameraAndRadiiAndDynamicAtmosphereColor; // Camera height, outer radius, inner radius, dynamic atmosphere color flag
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const float Kr = 0.0025;
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const float Kr4PI = Kr * 4.0 * czm_pi;
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const float Km = 0.0015;
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const float Km4PI = Km * 4.0 * czm_pi;
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const float ESun = 15.0;
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const float KmESun = Km * ESun;
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const float KrESun = Kr * ESun;
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const vec3 InvWavelength = vec3(
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5.60204474633241, // Red = 1.0 / Math.pow(0.650, 4.0)
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9.473284437923038, // Green = 1.0 / Math.pow(0.570, 4.0)
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19.643802610477206); // Blue = 1.0 / Math.pow(0.475, 4.0)
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const float rayleighScaleDepth = 0.25;
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const int nSamples = 2;
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const float fSamples = 2.0;
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varying vec3 v_rayleighColor;
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varying vec3 v_mieColor;
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varying vec3 v_toCamera;
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float scale(float cosAngle)
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{
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float x = 1.0 - cosAngle;
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return rayleighScaleDepth * exp(-0.00287 + x*(0.459 + x*(3.83 + x*(-6.80 + x*5.25))));
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}
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void main(void)
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{
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// Unpack attributes
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float cameraHeight = u_cameraAndRadiiAndDynamicAtmosphereColor.x;
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float outerRadius = u_cameraAndRadiiAndDynamicAtmosphereColor.y;
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float innerRadius = u_cameraAndRadiiAndDynamicAtmosphereColor.z;
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// Get the ray from the camera to the vertex and its length (which is the far point of the ray passing through the atmosphere)
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vec3 positionV3 = position.xyz;
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vec3 ray = positionV3 - czm_viewerPositionWC;
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float far = length(ray);
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ray /= far;
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float atmosphereScale = 1.0 / (outerRadius - innerRadius);
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#ifdef SKY_FROM_SPACE
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// Calculate the closest intersection of the ray with the outer atmosphere (which is the near point of the ray passing through the atmosphere)
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float B = 2.0 * dot(czm_viewerPositionWC, ray);
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float C = cameraHeight * cameraHeight - outerRadius * outerRadius;
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float det = max(0.0, B*B - 4.0 * C);
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float near = 0.5 * (-B - sqrt(det));
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// Calculate the ray's starting position, then calculate its scattering offset
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vec3 start = czm_viewerPositionWC + ray * near;
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far -= near;
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float startAngle = dot(ray, start) / outerRadius;
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float startDepth = exp(-1.0 / rayleighScaleDepth );
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float startOffset = startDepth*scale(startAngle);
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#else // SKY_FROM_ATMOSPHERE
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// Calculate the ray's starting position, then calculate its scattering offset
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vec3 start = czm_viewerPositionWC;
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float height = length(start);
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float depth = exp((atmosphereScale / rayleighScaleDepth ) * (innerRadius - cameraHeight));
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float startAngle = dot(ray, start) / height;
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float startOffset = depth*scale(startAngle);
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#endif
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float lightEnum = u_cameraAndRadiiAndDynamicAtmosphereColor.w;
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vec3 lightDirection =
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czm_viewerPositionWC * float(lightEnum == 0.0) +
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czm_lightDirectionWC * float(lightEnum == 1.0) +
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czm_sunDirectionWC * float(lightEnum == 2.0);
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lightDirection = normalize(lightDirection);
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// Initialize the scattering loop variables
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float sampleLength = far / fSamples;
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float scaledLength = sampleLength * atmosphereScale;
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vec3 sampleRay = ray * sampleLength;
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vec3 samplePoint = start + sampleRay * 0.5;
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// Now loop through the sample rays
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vec3 frontColor = vec3(0.0, 0.0, 0.0);
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for(int i=0; i<nSamples; i++)
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{
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float height = length(samplePoint);
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float depth = exp((atmosphereScale / rayleighScaleDepth ) * (innerRadius - height));
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float fLightAngle = dot(lightDirection, samplePoint) / height;
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float fCameraAngle = dot(ray, samplePoint) / height;
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float fScatter = (startOffset + depth*(scale(fLightAngle) - scale(fCameraAngle)));
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vec3 attenuate = exp(-fScatter * (InvWavelength * Kr4PI + Km4PI));
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frontColor += attenuate * (depth * scaledLength);
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samplePoint += sampleRay;
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}
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// Finally, scale the Mie and Rayleigh colors and set up the varying variables for the pixel shader
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v_mieColor = frontColor * KmESun;
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v_rayleighColor = frontColor * (InvWavelength * KrESun);
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v_toCamera = czm_viewerPositionWC - positionV3;
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gl_Position = czm_modelViewProjection * position;
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}
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