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114 lines
4.7 KiB
GLSL
114 lines
4.7 KiB
GLSL
#version 120
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//
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// For licensing information, see http://http.developer.nvidia.com/GPUGems/gpugems_app01.html:
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//
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// NVIDIA Statement on the Software
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//
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// The source code provided is freely distributable, so long as the NVIDIA header remains unaltered and user modifications are
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// detailed.
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//
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// No Warranty
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//
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// THE SOFTWARE AND ANY OTHER MATERIALS PROVIDED BY NVIDIA ON THE ENCLOSED CD-ROM ARE PROVIDED "AS IS." NVIDIA DISCLAIMS ALL
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// WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF TITLE, MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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//
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// Limitation of Liability
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//
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// NVIDIA SHALL NOT BE LIABLE TO ANY USER, DEVELOPER, DEVELOPER'S CUSTOMERS, OR ANY OTHER PERSON OR ENTITY CLAIMING THROUGH OR
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// UNDER DEVELOPER FOR ANY LOSS OF PROFITS, INCOME, SAVINGS, OR ANY OTHER CONSEQUENTIAL, INCIDENTAL, SPECIAL, PUNITIVE, DIRECT
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// OR INDIRECT DAMAGES (WHETHER IN AN ACTION IN CONTRACT, TORT OR BASED ON A WARRANTY), EVEN IF NVIDIA HAS BEEN ADVISED OF THE
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// POSSIBILITY OF SUCH DAMAGES. THESE LIMITATIONS SHALL APPLY NOTWITHSTANDING ANY FAILURE OF THE ESSENTIAL PURPOSE OF ANY
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// LIMITED REMEDY. IN NO EVENT SHALL NVIDIA'S AGGREGATE LIABILITY TO DEVELOPER OR ANY OTHER PERSON OR ENTITY CLAIMING THROUGH
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// OR UNDER DEVELOPER EXCEED THE AMOUNT OF MONEY ACTUALLY PAID BY DEVELOPER TO NVIDIA FOR THE SOFTWARE OR ANY OTHER MATERIALS.
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//
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//
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// Atmospheric scattering fragment shader
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//
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// Author: Sean O'Neil
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//
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// Copyright (c) 2004 Sean O'Neil
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//
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uniform vec3 v3CameraPos; // The camera's current position
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uniform vec3 v3LightPos; // The direction vector to the light source
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uniform vec3 v3InvWavelength; // 1 / pow(wavelength, 4) for the red, green, and blue channels
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uniform float fCameraHeight2; // fCameraHeight^2
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uniform float fOuterRadius; // The outer (atmosphere) radius
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uniform float fOuterRadius2; // fOuterRadius^2
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uniform float fInnerRadius; // The inner (planetary) radius
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uniform float fKrESun; // Kr * ESun
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uniform float fKmESun; // Km * ESun
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uniform float fKr4PI; // Kr * 4 * PI
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uniform float fKm4PI; // Km * 4 * PI
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uniform float fScale; // 1 / (fOuterRadius - fInnerRadius)
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uniform float fScaleDepth; // The scale depth (i.e. the altitude at which the atmosphere's average density is found)
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uniform float fScaleOverScaleDepth; // fScale / fScaleDepth
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uniform float g;
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uniform float g2;
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const int nSamples = 2;
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const float fSamples = 2.0;
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varying vec3 position;
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float scale(float fCos)
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{
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float x = 1.0 - fCos;
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return fScaleDepth * 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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// 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 v3Pos = position;
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vec3 v3Ray = v3Pos - v3CameraPos;
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float fFar = length(v3Ray);
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v3Ray /= fFar;
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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(v3CameraPos, v3Ray);
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float C = fCameraHeight2 - fOuterRadius2;
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float fDet = max(0.0, B*B - 4.0 * C);
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float fNear = 0.5 * (-B - sqrt(fDet));
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// Calculate the ray's starting position, then calculate its scattering offset
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vec3 v3Start = v3CameraPos + v3Ray * fNear;
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fFar -= fNear;
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float fStartAngle = dot(v3Ray, v3Start) / fOuterRadius;
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float fStartDepth = exp(-1.0 / fScaleDepth);
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float fStartOffset = fStartDepth * scale(fStartAngle);
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// Initialize the scattering loop variables
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//gl_FrontColor = vec4(0.0, 0.0, 0.0, 0.0);
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float fSampleLength = fFar / fSamples;
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float fScaledLength = fSampleLength * fScale;
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vec3 v3SampleRay = v3Ray * fSampleLength;
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vec3 v3SamplePoint = v3Start + v3SampleRay * 0.5;
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// Now loop through the sample rays
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vec3 v3FrontColor = 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 fHeight = length(v3SamplePoint);
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float fDepth = exp(fScaleOverScaleDepth * (fInnerRadius - fHeight));
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float fLightAngle = dot(v3LightPos, v3SamplePoint) / fHeight;
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float fCameraAngle = dot((v3Ray), v3SamplePoint) / fHeight * 0.99;
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float fScatter = (fStartOffset + fDepth * (scale(fLightAngle) - scale(fCameraAngle)));
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vec3 v3Attenuate = exp(-fScatter * (v3InvWavelength * fKr4PI + fKm4PI));
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v3FrontColor += v3Attenuate * (fDepth * fScaledLength);
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v3SamplePoint += v3SampleRay;
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}
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vec3 v3Direction = v3CameraPos - v3Pos;
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float fCos = dot(v3LightPos, v3Direction) / length(v3Direction);
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float fMiePhase = 1.5 * ((1.0 - g2) / (2.0 + g2)) * (1.0 + fCos*fCos) / pow(1.0 + g2 - 2.0*g*fCos, 1.5);
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vec3 color = v3FrontColor * (v3InvWavelength * fKrESun);
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vec3 secondaryColor = v3FrontColor * fKmESun;
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gl_FragColor.rgb = color + fMiePhase * secondaryColor;
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gl_FragColor.a = gl_FragColor.b;
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gl_FragColor.rgb = pow(gl_FragColor.rgb, vec3(1.0/2.2));
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}
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