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- /**
- * @license
- * 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 Cesium GS, Inc.
- */
- // Code: http://sponeil.net/
- // GPU Gems 2 Article: https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_chapter16.html
- const float Kr = 0.0025;
- const float Kr4PI = Kr * 4.0 * czm_pi;
- const float Km = 0.0015;
- const float Km4PI = Km * 4.0 * czm_pi;
- const float ESun = 15.0;
- const float KmESun = Km * ESun;
- const float KrESun = Kr * ESun;
- const vec3 InvWavelength = vec3(
- 5.60204474633241, // Red = 1.0 / Math.pow(0.650, 4.0)
- 9.473284437923038, // Green = 1.0 / Math.pow(0.570, 4.0)
- 19.643802610477206); // Blue = 1.0 / Math.pow(0.475, 4.0)
- const float rayleighScaleDepth = 0.25;
- const int nSamples = 2;
- const float fSamples = 2.0;
- const float g = -0.95;
- const float g2 = g * g;
- #ifdef COLOR_CORRECT
- uniform vec3 u_hsbShift; // Hue, saturation, brightness
- #endif
- uniform vec3 u_radiiAndDynamicAtmosphereColor; // outer radius, inner radius, dynamic atmosphere color flag
- float scale(float cosAngle)
- {
- float x = 1.0 - cosAngle;
- return rayleighScaleDepth * exp(-0.00287 + x*(0.459 + x*(3.83 + x*(-6.80 + x*5.25))));
- }
- vec3 getLightDirection(vec3 positionWC)
- {
- float lightEnum = u_radiiAndDynamicAtmosphereColor.z;
- vec3 lightDirection =
- positionWC * float(lightEnum == 0.0) +
- czm_lightDirectionWC * float(lightEnum == 1.0) +
- czm_sunDirectionWC * float(lightEnum == 2.0);
- return normalize(lightDirection);
- }
- void calculateRayScatteringFromSpace(in vec3 positionWC, in vec3 ray, in float innerRadius, in float outerRadius, inout float far, out vec3 start, out float startOffset)
- {
- // Calculate the closest intersection of the ray with the outer atmosphere (which is the near point of the ray passing through the atmosphere)
- float cameraHeight = length(positionWC);
- float B = 2.0 * dot(positionWC, ray);
- float C = cameraHeight * cameraHeight - outerRadius * outerRadius;
- float det = max(0.0, B * B - 4.0 * C);
- float near = 0.5 * (-B - sqrt(det));
- // Calculate the ray's starting position, then calculate its scattering offset
- start = positionWC + ray * near;
- far -= near;
- float startAngle = dot(ray, start) / outerRadius;
- float startDepth = exp(-1.0 / rayleighScaleDepth);
- startOffset = startDepth * scale(startAngle);
- }
- void calculateRayScatteringFromGround(in vec3 positionWC, in vec3 ray, in float atmosphereScale, in float innerRadius, out vec3 start, out float startOffset)
- {
- // Calculate the ray's starting position, then calculate its scattering offset
- float cameraHeight = length(positionWC);
- start = positionWC;
- float height = length(start);
- float depth = exp((atmosphereScale / rayleighScaleDepth ) * (innerRadius - cameraHeight));
- float startAngle = dot(ray, start) / height;
- startOffset = depth*scale(startAngle);
- }
- czm_raySegment rayEllipsoidIntersection(czm_ray ray, vec3 inverseRadii)
- {
- vec3 o = inverseRadii * (czm_inverseView * vec4(ray.origin, 1.0)).xyz;
- vec3 d = inverseRadii * (czm_inverseView * vec4(ray.direction, 0.0)).xyz;
- float a = dot(d, d);
- float b = dot(d, o);
- float c = dot(o, o) - 1.0;
- float discriminant = b * b - a * c;
- if (discriminant < 0.0)
- {
- return czm_emptyRaySegment;
- }
- discriminant = sqrt(discriminant);
- float t1 = (-b - discriminant) / a;
- float t2 = (-b + discriminant) / a;
- if (t1 < 0.0 && t2 < 0.0)
- {
- return czm_emptyRaySegment;
- }
- if (t1 < 0.0 && t2 >= 0.0)
- {
- t1 = 0.0;
- }
- return czm_raySegment(t1, t2);
- }
- vec3 getAdjustedPosition(vec3 positionWC, float innerRadius)
- {
- // Adjust the camera position so that atmosphere color looks the same wherever the eye height is the same
- float cameraHeight = czm_eyeHeight + innerRadius;
- return normalize(positionWC) * cameraHeight;
- }
- vec3 getTranslucentPosition(vec3 positionWC, vec3 outerPositionWC, float innerRadius, out bool intersectsEllipsoid)
- {
- vec3 directionWC = normalize(outerPositionWC - positionWC);
- vec3 directionEC = czm_viewRotation * directionWC;
- czm_ray viewRay = czm_ray(vec3(0.0), directionEC);
- czm_raySegment raySegment = rayEllipsoidIntersection(viewRay, czm_ellipsoidInverseRadii);
- intersectsEllipsoid = raySegment.start >= 0.0;
- if (intersectsEllipsoid)
- {
- return positionWC + raySegment.stop * directionWC;
- }
- return getAdjustedPosition(positionWC, innerRadius);
- }
- void calculateMieColorAndRayleighColor(vec3 outerPositionWC, out vec3 mieColor, out vec3 rayleighColor)
- {
- // Unpack attributes
- float outerRadius = u_radiiAndDynamicAtmosphereColor.x;
- float innerRadius = u_radiiAndDynamicAtmosphereColor.y;
- #ifdef GLOBE_TRANSLUCENT
- bool intersectsEllipsoid = false;
- vec3 startPositionWC = getTranslucentPosition(czm_viewerPositionWC, outerPositionWC, innerRadius, intersectsEllipsoid);
- #else
- vec3 startPositionWC = getAdjustedPosition(czm_viewerPositionWC, innerRadius);
- #endif
- vec3 lightDirection = getLightDirection(startPositionWC);
- // Get the ray from the start position to the outer position and its length (which is the far point of the ray passing through the atmosphere)
- vec3 ray = outerPositionWC - startPositionWC;
- float far = length(ray);
- ray /= far;
- float atmosphereScale = 1.0 / (outerRadius - innerRadius);
- vec3 start;
- float startOffset;
- #ifdef SKY_FROM_SPACE
- #ifdef GLOBE_TRANSLUCENT
- if (intersectsEllipsoid)
- {
- calculateRayScatteringFromGround(startPositionWC, ray, atmosphereScale, innerRadius, start, startOffset);
- }
- else
- {
- calculateRayScatteringFromSpace(startPositionWC, ray, innerRadius, outerRadius, far, start, startOffset);
- }
- #else
- calculateRayScatteringFromSpace(startPositionWC, ray, innerRadius, outerRadius, far, start, startOffset);
- #endif
- #else
- calculateRayScatteringFromGround(startPositionWC, ray, atmosphereScale, innerRadius, start, startOffset);
- #endif
- // Initialize the scattering loop variables
- float sampleLength = far / fSamples;
- float scaledLength = sampleLength * atmosphereScale;
- vec3 sampleRay = ray * sampleLength;
- vec3 samplePoint = start + sampleRay * 0.5;
- // Now loop through the sample rays
- vec3 frontColor = vec3(0.0, 0.0, 0.0);
- for (int i = 0; i<nSamples; i++)
- {
- float height = length(samplePoint);
- float depth = exp((atmosphereScale / rayleighScaleDepth ) * (innerRadius - height));
- float fLightAngle = dot(lightDirection, samplePoint) / height;
- float fCameraAngle = dot(ray, samplePoint) / height;
- float fScatter = (startOffset + depth*(scale(fLightAngle) - scale(fCameraAngle)));
- vec3 attenuate = exp(-fScatter * (InvWavelength * Kr4PI + Km4PI));
- frontColor += attenuate * (depth * scaledLength);
- samplePoint += sampleRay;
- }
- // Finally, scale the Mie and Rayleigh colors and set up the varying variables for the pixel shader
- mieColor = frontColor * KmESun;
- rayleighColor = frontColor * (InvWavelength * KrESun);
- // Cap mie and rayleigh colors to prevent NaNs when vertex interpolation happens
- mieColor = min(mieColor, vec3(10000000.0));
- rayleighColor = min(rayleighColor, vec3(10000000.0));
- }
- vec4 calculateFinalColor(vec3 positionWC, vec3 toCamera, vec3 lightDirection, vec3 mieColor, vec3 rayleighColor)
- {
- // Extra normalize added for Android
- float cosAngle = dot(lightDirection, normalize(toCamera)) / length(toCamera);
- float rayleighPhase = 0.75 * (1.0 + cosAngle * cosAngle);
- float miePhase = 1.5 * ((1.0 - g2) / (2.0 + g2)) * (1.0 + cosAngle * cosAngle) / pow(1.0 + g2 - 2.0 * g * cosAngle, 1.5);
- vec3 rgb = rayleighPhase * rayleighColor + miePhase * mieColor;
- const float exposure = 2.0;
- vec3 rgbExposure = vec3(1.0) - exp(-exposure * rgb);
- #ifndef HDR
- rgb = rgbExposure;
- #endif
- #ifdef COLOR_CORRECT
- // Convert rgb color to hsb
- vec3 hsb = czm_RGBToHSB(rgb);
- // Perform hsb shift
- hsb.x += u_hsbShift.x; // hue
- hsb.y = clamp(hsb.y + u_hsbShift.y, 0.0, 1.0); // saturation
- hsb.z = hsb.z > czm_epsilon7 ? hsb.z + u_hsbShift.z : 0.0; // brightness
- // Convert shifted hsb back to rgb
- rgb = czm_HSBToRGB(hsb);
- #endif
- float outerRadius = u_radiiAndDynamicAtmosphereColor.x;
- float innerRadius = u_radiiAndDynamicAtmosphereColor.y;
- float lightEnum = u_radiiAndDynamicAtmosphereColor.z;
- float cameraHeight = czm_eyeHeight + innerRadius;
- // Alter alpha based on how close the viewer is to the ground (1.0 = on ground, 0.0 = at edge of atmosphere)
- float atmosphereAlpha = clamp((outerRadius - cameraHeight) / (outerRadius - innerRadius), 0.0, 1.0);
- // Alter alpha based on time of day (0.0 = night , 1.0 = day)
- float nightAlpha = (lightEnum != 0.0) ? clamp(dot(normalize(positionWC), lightDirection), 0.0, 1.0) : 1.0;
- atmosphereAlpha *= pow(nightAlpha, 0.5);
- vec4 finalColor = vec4(rgb, mix(clamp(rgbExposure.b, 0.0, 1.0), 1.0, atmosphereAlpha) * smoothstep(0.0, 1.0, czm_morphTime));
- if (mieColor.b > 1.0)
- {
- // Fade atmosphere below the ellipsoid. As the camera zooms further away from the ellipsoid draw
- // a larger atmosphere ring to cover empty space of lower LOD globe tiles.
- float strength = mieColor.b;
- float minDistance = outerRadius;
- float maxDistance = outerRadius * 3.0;
- float maxStrengthLerp = 1.0 - clamp((maxDistance - cameraHeight) / (maxDistance - minDistance), 0.0, 1.0);
- float maxStrength = mix(100.0, 10000.0, maxStrengthLerp);
- strength = min(strength, maxStrength);
- float alpha = 1.0 - (strength / maxStrength);
- finalColor.a = alpha;
- }
- return finalColor;
- }
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