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skydome object
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tmj-fstate
332
skydome.cpp
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332
skydome.cpp
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//******************************************************************************//
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// NightShine Engine //
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// Sky : Gradient SkyDome Class //
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//******************************************************************************//
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// sky gradient based on "A practical analytic model for daylight"
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// by A. J. Preetham Peter Shirley Brian Smits (University of Utah)
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#include "stdafx.h"
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#include "opengl/glew.h"
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#include "skydome.h"
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#include "color.h"
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//******************************************************************************//
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float CSkyDome::m_distributionluminance[ 5 ][ 2 ] = { // Perez distributions
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{ 0.17872f , -1.46303f }, // a = darkening or brightening of the horizon
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{ -0.35540f , 0.42749f }, // b = luminance gradient near the horizon,
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{ -0.02266f , 5.32505f }, // c = relative intensity of the circumsolar region
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{ 0.12064f , -2.57705f }, // d = width of the circumsolar region
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{ -0.06696f , 0.37027f } // e = relative backscattered light
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};
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float CSkyDome::m_distributionxcomp[ 5 ][ 2 ] = {
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{ -0.01925f , -0.25922f },
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{ -0.06651f , 0.00081f },
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{ -0.00041f , 0.21247f },
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{ -0.06409f , -0.89887f },
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{ -0.00325f , 0.04517f }
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};
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float CSkyDome::m_distributionycomp[ 5 ][ 2 ] = {
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{ -0.01669f , -0.26078f },
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{ -0.09495f , 0.00921f },
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{ -0.00792f , 0.21023f },
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{ -0.04405f , -1.65369f },
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{ -0.01092f , 0.05291f }
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};
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float CSkyDome::m_zenithxmatrix[ 3 ][ 4 ] = {
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{ 0.00165f, -0.00375f, 0.00209f, 0.00000f },
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{ -0.02903f, 0.06377f, -0.03202f, 0.00394f },
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{ 0.11693f, -0.21196f, 0.06052f, 0.25886f }
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};
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float CSkyDome::m_zenithymatrix[ 3 ][ 4 ] = {
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{ 0.00275f, -0.00610f, 0.00317f, 0.00000f },
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{ -0.04214f, 0.08970f, -0.04153f, 0.00516f },
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{ 0.15346f, -0.26756f, 0.06670f, 0.26688f }
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};
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//******************************************************************************//
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float clamp( float const Value, float const Min, float const Max ) {
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float value = Value;
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if( value < Min ) { value = Min; }
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if( value > Max ) { value = Max; }
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return value;
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}
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float interpolate( float const First, float const Second, float const Factor ) {
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return ( First * ( 1.0f - Factor ) ) + ( Second * Factor );
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}
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//******************************************************************************//
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CSkyDome::CSkyDome (int const Tesselation) :
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m_tesselation( Tesselation ) {
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// SetSunPosition( Math3D::vector3(75.0f, 0.0f, 0.0f) );
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SetTurbidity( 3.5f );
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SetExposure( true, 16.0f );
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SetOvercastFactor( 0.08f );
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SetGammaCorrection( 2.2f );
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Generate();
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}
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CSkyDome::~CSkyDome() {
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}
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//******************************************************************************//
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void CSkyDome::Generate() {
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// radius of dome
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float const radius = 1.0f; // 100.0f;
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// create geometry chunk
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int const latitudes = m_tesselation / 2;
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int const longitudes = m_tesselation;
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for( int i = 0; i < latitudes; ++i ) {
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float lat0 = M_PI * ( -0.5f + (float)( i ) / latitudes );
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float z0 = std::sin( lat0 );
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float zr0 = std::cos( lat0 );
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float lat1 = M_PI * ( -0.5f + (float)( i + 1 ) / latitudes );
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float z1 = std::sin( lat1 );
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float zr1 = std::cos( lat1 );
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// quad strip
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for( int j = 0; j <= longitudes / 2; ++j ) {
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float longitude = 2.0 * M_PI * (float)( j ) / longitudes;
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float x = std::cos( longitude );
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float y = std::sin( longitude );
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m_vertices.emplace_back( float3( x * zr0, y * zr0 - 0.1f, z0 ) * radius );
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// m_normals.emplace_back( float3( -x * zr0, -y * zr0, -z0 ) );
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m_colours.emplace_back( float3( 0.75f, 0.75f, 0.75f ) );
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m_vertices.emplace_back( float3( x * zr1, y * zr1 - 0.1f, z1 ) * radius );
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// m_normals.emplace_back( float3( -x * zr1, -y * zr1, -z1 ) );
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m_colours.emplace_back( float3( 0.75f, 0.75f, 0.75f ) );
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}
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}
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}
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//******************************************************************************//
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void CSkyDome::Update( Math3D::vector3 const &Sun ) {
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if( true == SetSunPosition( Sun ) ) {
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// build colors if there's a change in sun position
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RebuildColors();
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}
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}
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// render skydome to screen
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void CSkyDome::Render() {
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int const latitudes = m_tesselation / 2;
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int const longitudes = m_tesselation;
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int idx = 0;
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for( int i = 0; i < latitudes; ++i ) {
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::glBegin( GL_QUAD_STRIP );
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for( int j = 0; j <= longitudes / 2; ++j ) {
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::glColor3f( m_colours[ idx ].x, m_colours[ idx ].y, m_colours[ idx ].z );
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// ::glNormal3f( m_normals[ idx ].x, m_normals[ idx ].y, m_normals[ idx ].z );
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::glVertex3f( m_vertices[ idx ].x, m_vertices[ idx ].y, m_vertices[ idx ].z );
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++idx;
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::glColor3f( m_colours[ idx ].x, m_colours[ idx ].y, m_colours[ idx ].z );
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// ::glNormal3f( m_normals[ idx ].x, m_normals[ idx ].y, m_normals[ idx ].z );
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::glVertex3f( m_vertices[ idx ].x, m_vertices[ idx ].y, m_vertices[ idx ].z );
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++idx;
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}
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glEnd();
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}
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}
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//******************************************************************************//
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bool CSkyDome::SetSunPosition( Math3D::vector3 const &Direction ) {
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auto sundirection = SafeNormalize( float3( Direction.x, Direction.y, Direction.z) );
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if( sundirection == m_sundirection ) {
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return false;
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}
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m_sundirection = sundirection;
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m_thetasun = std::acosf( m_sundirection.y );
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m_phisun = std::atan2( m_sundirection.z , m_sundirection.x );
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return true;
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}
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void CSkyDome::SetTurbidity( float const Turbidity ) {
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m_turbidity = clamp( Turbidity, 1.0f, 512.0f );
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}
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void CSkyDome::SetExposure( bool const Linearexposure, float const Expfactor ) {
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m_linearexpcontrol = Linearexposure;
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m_expfactor = 1.0f / clamp( Expfactor, 1.0f, std::numeric_limits<float>::infinity() );
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}
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void CSkyDome::SetGammaCorrection( float const Gamma ) {
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m_gammacorrection = 1.0f / clamp( Gamma, std::numeric_limits<float>::epsilon(), std::numeric_limits<float>::infinity() );
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}
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void CSkyDome::SetOvercastFactor( float const Overcast ) {
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m_overcast = clamp( Overcast, 0.0f, 1.0f );
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}
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//******************************************************************************//
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void CSkyDome::GetPerez( float *Perez, float Distribution[ 5 ][ 2 ], const float Turbidity ) {
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Perez[ 0 ] = Distribution[ 0 ][ 0 ] * Turbidity + Distribution[ 0 ][ 1 ];
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Perez[ 1 ] = Distribution[ 1 ][ 0 ] * Turbidity + Distribution[ 1 ][ 1 ];
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Perez[ 2 ] = Distribution[ 2 ][ 0 ] * Turbidity + Distribution[ 2 ][ 1 ];
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Perez[ 3 ] = Distribution[ 3 ][ 0 ] * Turbidity + Distribution[ 3 ][ 1 ];
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Perez[ 4 ] = Distribution[ 4 ][ 0 ] * Turbidity + Distribution[ 4 ][ 1 ];
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}
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float CSkyDome::GetZenith( float Zenithmatrix[ 3 ][ 4 ], const float Theta, const float Turbidity ) {
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const float theta2 = Theta*Theta;
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const float theta3 = Theta*theta2;
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return ( Zenithmatrix[0][0] * theta3 + Zenithmatrix[0][1] * theta2 + Zenithmatrix[0][2] * Theta + Zenithmatrix[0][3]) * Turbidity * Turbidity +
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( Zenithmatrix[1][0] * theta3 + Zenithmatrix[1][1] * theta2 + Zenithmatrix[1][2] * Theta + Zenithmatrix[1][3]) * Turbidity +
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( Zenithmatrix[2][0] * theta3 + Zenithmatrix[2][1] * theta2 + Zenithmatrix[2][2] * Theta + Zenithmatrix[2][3]);
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}
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//******************************************************************************//
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float CSkyDome::PerezFunctionO1( float Perezcoeffs[ 5 ], const float Thetasun, const float Zenithval ) {
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const float val = ( 1.0f + Perezcoeffs[ 0 ] * std::exp( Perezcoeffs[ 1 ] ) ) *
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( 1.0f + Perezcoeffs[ 2 ] * std::exp( Perezcoeffs[ 3 ] * Thetasun ) + Perezcoeffs[ 4 ] * std::pow( std::cos( Thetasun ), 2 ) );
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return Zenithval / val;
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}
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float CSkyDome::PerezFunctionO2( float Perezcoeffs[ 5 ], const float Icostheta, const float Gamma, const float Cosgamma2, const float Zenithval ) {
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// iCosTheta = 1.0f / cosf(theta)
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// cosGamma2 = SQR( cosf( gamma ) )
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return Zenithval * ( 1.0f + Perezcoeffs[ 0 ] * std::exp( Perezcoeffs[ 1 ] * Icostheta ) ) *
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( 1.0f + Perezcoeffs[ 2 ] * std::exp( Perezcoeffs[ 3 ] * Gamma ) + Perezcoeffs[ 4 ] * Cosgamma2 );
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}
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//******************************************************************************//
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void CSkyDome::RebuildColors() {
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// get zenith luminance
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float const chi = ( (4.0f / 9.0f) - (m_turbidity / 120.0f) ) * ( M_PI - (2.0f * m_thetasun) );
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float zenithluminance = ( (4.0453f * m_turbidity) - 4.9710f ) * std::tan( chi ) - (0.2155f * m_turbidity) + 2.4192f;
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// get x / y zenith
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float zenithx = GetZenith( m_zenithxmatrix, m_thetasun, m_turbidity );
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float zenithy = GetZenith( m_zenithymatrix, m_thetasun, m_turbidity );
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// get perez function parametrs
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float perezluminance[5], perezx[5], perezy[5];
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GetPerez( perezluminance, m_distributionluminance, m_turbidity );
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GetPerez( perezx, m_distributionxcomp, m_turbidity );
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GetPerez( perezy, m_distributionycomp, m_turbidity );
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// make some precalculation
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zenithx = PerezFunctionO1( perezx, m_thetasun, zenithx );
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zenithy = PerezFunctionO1( perezy, m_thetasun, zenithy );
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zenithluminance = PerezFunctionO1( perezluminance, m_thetasun, zenithluminance );
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// start with fresh average for the new pass
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float3 averagecolor{ 0.0f, 0.0f, 0.0f };
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// trough all vertices
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float3 vertex;
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float3 color, colorconverter;
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for ( unsigned int i = 0; i < m_vertices.size(); ++i ) {
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// grab it
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vertex = SafeNormalize( m_vertices[ i ] );
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// angle between sun and vertex
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const float gamma = std::acos( DotProduct( vertex, m_sundirection ) );
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// warning : major hack!!! .. i had to do something with values under horizon
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//vertex.y = Clamp<float>( vertex.y, 0.05f, 1.0f );
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if ( vertex.y < 0.05f ) vertex.y = 0.05f;
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// from paper:
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// const float theta = arccos( vertex.y );
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// const float iCosTheta = 1.0f / cosf( theta );
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// optimized:
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// iCosTheta =
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// = 1.0f / cosf( arccos( vertex.y ) );
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// = 1.0f / vertex.y;
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float const icostheta = 1.0f / vertex.y;
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float const cosgamma2 = std::pow( std::cos( gamma ), 2 );
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// Compute x,y values
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float const x = PerezFunctionO2( perezx, icostheta, gamma, cosgamma2, zenithx );
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float const y = PerezFunctionO2( perezy, icostheta, gamma, cosgamma2, zenithy );
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// luminance(Y) for clear & overcast sky
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float const yclear = PerezFunctionO2( perezluminance, icostheta, gamma, cosgamma2, zenithluminance );
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float const yover = ( 1.0f + 2.0f * vertex.y ) / 3.0f;
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float const Y = interpolate( yclear, yover, m_overcast );
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float const X = (x / y) * Y;
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float const Z = ((1.0f - x - y) / y) * Y;
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colorconverter = float3( X, Y, Z );
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color = XYZtoRGB( colorconverter );
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colorconverter = RGBtoHSV(color);
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if ( m_linearexpcontrol ) {
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// linear scale
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colorconverter.z *= m_expfactor;
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} else {
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// exp scale
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colorconverter.z = 1.0f - exp( -m_expfactor * colorconverter.z );
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}
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color = HSVtoRGB(colorconverter);
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/*
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// gamma control
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color.x = std::pow( color.x, m_gammacorrection );
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color.x = std::pow( color.y, m_gammacorrection );
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color.x = std::pow( color.z, m_gammacorrection );
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*/
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// crude correction for the times where the model breaks (late night)
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// TODO: use proper night sky calculation for these times instead
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if( ( color.x <= 0.0f )
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&& ( color.y <= 0.0f ) ) {
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// darken the sky as the sun goes deeper below the horizon
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// 15:50:75 is picture-based night sky colour. it may not be accurate but looks 'right enough'
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color.z = 0.75f * std::max( color.z + m_sundirection.y, 0.075f );
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color.x = 0.20f * color.z;
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color.y = 0.65f * color.z;
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}
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// save
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m_colours[ i ] = color;
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averagecolor += color;
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}
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m_averagecolour = averagecolor / m_vertices.size();
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m_averagecolour.x = std::max( m_averagecolour.x, 0.0f );
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m_averagecolour.y = std::max( m_averagecolour.y, 0.0f );
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m_averagecolour.z = std::max( m_averagecolour.z, 0.0f );
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}
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//******************************************************************************//
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