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- const float Kr = 0.0025;
- const float Km = 0.0015;
- const float ESun = 15.0;
- const float fKrESun = Kr * ESun;
- const float fKmESun = Km * ESun;
- const float fKr4PI = Kr * 4.0 * czm_pi;
- const float fKm4PI = Km * 4.0 * czm_pi;
- const vec3 v3InvWavelength = vec3(5.60204474633241, 9.473284437923038, 19.64380261047721);
- const float fScaleDepth = 0.25;
- struct AtmosphereColor
- {
- vec3 mie;
- vec3 rayleigh;
- };
- const int nSamples = 2;
- const float fSamples = 2.0;
- float scale(float fCos)
- {
- float x = 1.0 - fCos;
- return fScaleDepth * exp(-0.00287 + x*(0.459 + x*(3.83 + x*(-6.80 + x*5.25))));
- }
- AtmosphereColor computeGroundAtmosphereFromSpace(vec3 v3Pos, bool dynamicLighting, vec3 lightDirectionWC)
- {
- float fInnerRadius = czm_ellipsoidRadii.x;
- float fOuterRadius = czm_ellipsoidRadii.x * 1.025;
- float fOuterRadius2 = fOuterRadius * fOuterRadius;
- float fScale = 1.0 / (fOuterRadius - fInnerRadius);
- float fScaleOverScaleDepth = fScale / fScaleDepth;
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- vec3 v3Ray = v3Pos - czm_viewerPositionWC;
- float fFar = length(v3Ray);
- v3Ray /= fFar;
- float fCameraHeight = length(czm_viewerPositionWC);
- float fCameraHeight2 = fCameraHeight * fCameraHeight;
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- float B = 2.0 * length(czm_viewerPositionWC) * dot(normalize(czm_viewerPositionWC), v3Ray);
- float C = fCameraHeight2 - fOuterRadius2;
- float fDet = max(0.0, B*B - 4.0 * C);
- float fNear = 0.5 * (-B - sqrt(fDet));
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- vec3 v3Start = czm_viewerPositionWC + v3Ray * fNear;
- fFar -= fNear;
- float fDepth = exp((fInnerRadius - fOuterRadius) / fScaleDepth);
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- float fLightAngle = czm_branchFreeTernary(dynamicLighting, dot(lightDirectionWC, v3Pos) / length(v3Pos), 1.0);
- float fCameraAngle = dot(-v3Ray, v3Pos) / length(v3Pos);
- float fCameraScale = scale(fCameraAngle);
- float fLightScale = scale(fLightAngle);
- float fCameraOffset = fDepth*fCameraScale;
- float fTemp = (fLightScale + fCameraScale);
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- float fSampleLength = fFar / fSamples;
- float fScaledLength = fSampleLength * fScale;
- vec3 v3SampleRay = v3Ray * fSampleLength;
- vec3 v3SamplePoint = v3Start + v3SampleRay * 0.5;
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- vec3 v3FrontColor = vec3(0.0);
- vec3 v3Attenuate = vec3(0.0);
- for(int i=0; i<nSamples; i++)
- {
- float fHeight = length(v3SamplePoint);
- float fDepth = exp(fScaleOverScaleDepth * (fInnerRadius - fHeight));
- float fScatter = fDepth*fTemp - fCameraOffset;
- v3Attenuate = exp(-fScatter * (v3InvWavelength * fKr4PI + fKm4PI));
- v3FrontColor += v3Attenuate * (fDepth * fScaledLength);
- v3SamplePoint += v3SampleRay;
- }
- AtmosphereColor color;
- color.mie = v3FrontColor * (v3InvWavelength * fKrESun + fKmESun);
- color.rayleigh = v3Attenuate;
- return color;
- }
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