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#include "AtmosphereShadersCommon.fxh"
#ifndef THREAD_GROUP_SIZE
# define THREAD_GROUP_SIZE 16
#endif
cbuffer cbParticipatingMediaScatteringParams
{
AirScatteringAttribs g_MediaParams;
}
Texture2D<float2> g_tex2DOccludedNetDensityToAtmTop;
SamplerState g_tex2DOccludedNetDensityToAtmTop_sampler;
#include "LookUpTables.fxh"
#include "ScatteringIntegrals.fxh"
#include "PrecomputeCommon.fxh"
RWTexture3D</*format = rgba16f*/float3> g_rwtex3DSingleScattering;
// This shader pre-computes the radiance of single scattering at a given point in given
// direction.
[numthreads(THREAD_GROUP_SIZE, THREAD_GROUP_SIZE, 1)]
void PrecomputeSingleScatteringCS(uint3 ThreadId : SV_DispatchThreadID)
{
// Get attributes for the current point
float4 f4LUTCoords = LUTCoordsFromThreadID(ThreadId);
float fAltitude, fCosViewZenithAngle, fCosSunZenithAngle, fCosSunViewAngle;
InsctrLUTCoords2WorldParams(f4LUTCoords,
g_MediaParams.fEarthRadius,
g_MediaParams.fAtmBottomAltitude,
g_MediaParams.fAtmTopAltitude,
fAltitude,
fCosViewZenithAngle,
fCosSunZenithAngle,
fCosSunViewAngle );
float3 f3EarthCentre = float3(0.0, -g_MediaParams.fEarthRadius, 0.0);
float3 f3RayStart = float3(0.0, fAltitude, 0.0);
float3 f3ViewDir = ComputeViewDir(fCosViewZenithAngle);
float3 f3DirOnLight = ComputeLightDir(f3ViewDir, fCosSunZenithAngle, fCosSunViewAngle);
// Intersect view ray with the atmosphere boundaries
float4 f4Isecs;
GetRaySphereIntersection2( f3RayStart, f3ViewDir, f3EarthCentre,
float2(g_MediaParams.fAtmBottomRadius, g_MediaParams.fAtmTopRadius),
f4Isecs);
float2 f2RayEarthIsecs = f4Isecs.xy;
float2 f2RayAtmTopIsecs = f4Isecs.zw;
if(f2RayAtmTopIsecs.y <= 0.0)
{
// This is just a sanity check and should never happen
// as the start point is always under the top of the
// atmosphere (look at InsctrLUTCoords2WorldParams())
g_rwtex3DSingleScattering[ThreadId] = float3(0.0, 0.0, 0.0);
return;
}
// Set the ray length to the distance to the top of the atmosphere
float fRayLength = f2RayAtmTopIsecs.y;
// If ray hits Earth, limit the length by the distance to the surface
if(f2RayEarthIsecs.x > 0.0)
fRayLength = min(fRayLength, f2RayEarthIsecs.x);
float3 f3RayEnd = f3RayStart + f3ViewDir * fRayLength;
// Integrate single-scattering
float3 f3Extinction, f3Inscattering;
IntegrateUnshadowedInscattering(f3RayStart,
f3RayEnd,
f3ViewDir,
f3EarthCentre,
g_MediaParams.fEarthRadius,
g_MediaParams.fAtmBottomAltitude,
g_MediaParams.fAtmAltitudeRangeInv,
g_MediaParams.f4ParticleScaleHeight,
f3DirOnLight.xyz,
100u,
f3Inscattering,
f3Extinction);
g_rwtex3DSingleScattering[ThreadId] = f3Inscattering;
}
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