123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132 |
- /*!
- * Atmosphere code:
- *
- * Copyright (c) 2000-2005, Sean O'Neil (s_p_oneil@hotmail.com)
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * * Redistributions of source code must retain the above copyright notice,
- * this list of conditions and the following disclaimer.
- * * Redistributions in binary form must reproduce the above copyright notice,
- * this list of conditions and the following disclaimer in the documentation
- * and/or other materials provided with the distribution.
- * * Neither the name of the project nor the names of its contributors may be
- * used to endorse or promote products derived from this software without
- * specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
- * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
- * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
- * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- * Modifications made by Analytical Graphics, Inc.
- */
- // Atmosphere:
- // Code: http://sponeil.net/
- // GPU Gems 2 Article: https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_chapter16.html
- 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;
- // Original: vec3(1.0 / pow(0.650, 4.0), 1.0 / pow(0.570, 4.0), 1.0 / pow(0.475, 4.0));
- 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;
- // Get the ray from the camera to the vertex and its length (which is the far point of the ray passing through the atmosphere)
- vec3 v3Ray = v3Pos - czm_viewerPositionWC;
- float fFar = length(v3Ray);
- v3Ray /= fFar;
- float fCameraHeight = length(czm_viewerPositionWC);
- float fCameraHeight2 = fCameraHeight * fCameraHeight;
- // This next line is an ANGLE workaround. It is equivalent to B = 2.0 * dot(czm_viewerPositionWC, v3Ray),
- // which is what it should be, but there are problems at the poles.
- 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));
- // Calculate the ray's starting position, then calculate its scattering offset
- vec3 v3Start = czm_viewerPositionWC + v3Ray * fNear;
- fFar -= fNear;
- float fDepth = exp((fInnerRadius - fOuterRadius) / fScaleDepth);
- // The light angle based on the scene's light source would be:
- // dot(lightDirectionWC, v3Pos) / length(v3Pos);
- // When we want the atmosphere to be uniform over the globe so it is set to 1.0.
- 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);
- // Initialize the scattering loop variables
- float fSampleLength = fFar / fSamples;
- float fScaledLength = fSampleLength * fScale;
- vec3 v3SampleRay = v3Ray * fSampleLength;
- vec3 v3SamplePoint = v3Start + v3SampleRay * 0.5;
- // Now loop through the sample rays
- 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; // Calculate the attenuation factor for the ground
- return color;
- }
|