/// <summary>
/// Builds a 3D lookup texture containing the scattering values for a parameterization of
/// the view frame and sun position.
/// </summary>
/// <param name="parameters">Parameters for the build process</param>
/// <param name="progress">Progress object</param>
/// <param name="voxels">3d texture voxels</param>
/// <returns>true if build completed (wasn't cancelled)</returns>
private unsafe bool BuildScatteringTexture( AtmosphereBuildParameters parameters, byte* voxels, AtmosphereBuildProgress progress )
{
float viewAngle = Constants.Pi;
float viewAngleInc = Constants.Pi / ( parameters.ViewAngleSamples - 1 );
float heightRange = ( m_OuterRadius - m_InnerRadius );
float heightInc = ( heightRange * 0.9999f ) / ( parameters.HeightSamples - 1 ); // Push height range in slightly to allow simplification of sphere intersections
float sunAngleInc = ( Constants.Pi ) / ( parameters.SunAngleSamples - 1 );
for ( int viewAngleSample = 0; viewAngleSample < parameters.ViewAngleSamples; ++viewAngleSample, viewAngle -= viewAngleInc )
{
Vector3 viewDir = new Vector3( Functions.Sin( viewAngle ), Functions.Cos( viewAngle ), 0 );
float sunAngle = 0;
for ( int sunAngleSample = 0; sunAngleSample < parameters.SunAngleSamples; ++sunAngleSample, sunAngle += sunAngleInc )
{
Vector3 sunDir = new Vector3( Functions.Sin( sunAngle ), Functions.Cos( sunAngle ), 0 );
float height = m_InnerRadius;
for ( int heightSample = 0; heightSample < parameters.HeightSamples; ++heightSample, height += heightInc )
{
ComputeScattering( viewDir, sunDir, height, voxels );
voxels += 4;
}
}
if ( progress != null )
{
progress.OnSliceCompleted( viewAngleSample / ( float )( parameters.ViewAngleSamples - 1 ) );
if ( progress.Cancel )
{
return false;
}
}
}
return true;
}
/// <summary>
/// Builds a 2D lookup texture containing optical depth for a paramerization of the view frame
/// </summary>
/// <param name="buildParams">Atmosphere build parameters</param>
/// <param name="pixels">Atmosphere texture pixels</param>
/// <param name="progress">Progress indicator</param>
/// <returns>Returns true if the build completed (wasn't cancelled)</returns>
private unsafe bool BuildOpticalDepthTexture( AtmosphereBuildParameters buildParams, byte* pixels, AtmosphereBuildProgress progress )
{
// TODO: AP: Because we know that the view to pos angle range will never be > pi, can optimise this later
int viewSamples = buildParams.OpticalDepthResolution;
int heightSamples = buildParams.OpticalDepthResolution;
float viewAngleInc = Constants.Pi / ( viewSamples - 1 );
float heightRange = ( m_OuterRadius - m_InnerRadius );
float heightInc = ( heightRange * 0.9999f ) / ( heightSamples - 1 ); // Push height range in slightly to allow simplification of sphere intersections
float* rAccum = stackalloc float[ 3 ];
float* mAccum = stackalloc float[ 3 ];
float height = m_InnerRadius;
for ( int heightSample = 0; heightSample < heightSamples; ++heightSample, height += heightInc )
{
Point3 pos = new Point3( 0, height, 0 );
// Start the view angle at pi, and count down to 0. This is because it is quickest to address
// the 2D texture using the dot of the view vector and the view position, saving a (1-th) operation
float viewAngle = Constants.Pi;
Point3 lastAtmInt = pos;
for ( int viewSample = 0; viewSample < viewSamples; ++viewSample, viewAngle -= viewAngleInc )
{
Vector3 viewDir = new Vector3( Functions.Sin( viewAngle ), Functions.Cos( viewAngle ), 0 );
// NOTE: If ray intersection fails, the previous intersection position is used...
Point3 atmInt;
// if ( !GetRayPlanetAndAtmosphereIntersection( pos, viewDir, out atmInt ) )
if ( !GetRayAtmosphereIntersection( pos, viewDir, out atmInt ) )
{
atmInt = lastAtmInt;
}
else
{
lastAtmInt = atmInt;
}
Vector3 step = ( atmInt - pos ) / m_AttenuationSamples;
rAccum[ 0 ] = rAccum[ 1 ] = rAccum[ 2 ] = 0;
mAccum[ 0 ] = mAccum[ 1 ] = mAccum[ 2 ] = 0;
CalculateOutScatter( pos, step, rAccum, mAccum );
// float oR = CalculateCombinedOutScatter( pos, step, m_RayleighCoefficients[ 0 ], m_MieCoefficients[ 0 ] );
// float oG = CalculateCombinedOutScatter( pos, step, m_RayleighCoefficients[ 1 ], m_MieCoefficients[ 1 ] );
// float oB = CalculateCombinedOutScatter( pos, step, m_RayleighCoefficients[ 2 ], m_MieCoefficients[ 2 ] );
float attR = ExtinctionCoefficient( rAccum[ 0 ], mAccum[ 0 ] );
float attG = ExtinctionCoefficient( rAccum[ 1 ], mAccum[ 1 ] );
float attB = ExtinctionCoefficient( rAccum[ 2 ], mAccum[ 2 ] );
pixels[ 2 ] = ( byte )( Utils.Clamp( attR, 0, 1 ) * 255.0f );
pixels[ 1 ] = ( byte )( Utils.Clamp( attG, 0, 1 ) * 255.0f );
pixels[ 0 ] = ( byte )( Utils.Clamp( attB, 0, 1 ) * 255.0f );
pixels += 3;
}
if ( progress != null )
{
progress.OnSliceCompleted( heightSample / ( float )( heightSamples - 1 ) );
if ( progress.Cancel )
{
return false;
}
}
}
return true;
}