/*==========================================================================*/
inline float Shader::Phong::attenuation( const kvs::Vector3f& vertex, const kvs::Vector3f& gradient ) const
{
// Light vector L, normal vector N and reflection vector R.
const kvs::Vector3f L = ( light_position - vertex ).normalized();
const kvs::Vector3f N = gradient.normalized();
const kvs::Vector3f R = 2.0f * N.dot( L ) * N - L;
const float dd = Math::Max( N.dot( L ), 0.0f );
const float ds = Math::Max( N.dot( R ), 0.0f );
/* I = Ia + Id + Is
*
* Is = Ip * Ks * cos^s(B) = Ip * Ks * ( R dot N )^s
*/
const float Ia = Ka;
const float Id = Kd * dd;
const float Is = Ks * std::pow( ds, S );
return Ia + Id + Is;
}
/*===========================================================================*/
const kvs::RGBColor Shader::Phong::shadedColor(
const kvs::RGBColor& color,
const kvs::Vector3f& vertex,
const kvs::Vector3f& normal ) const
{
// Light vector L, normal vector N and reflection vector R.
const kvs::Vector3f V = ( camera_position - vertex ).normalized();
const kvs::Vector3f L = ( light_position - vertex ).normalized();
const kvs::Vector3f N = normal.normalized();
const kvs::Vector3f R = 2.0f * N.dot( L ) * N - L;
// Intensity values.
const float Ia = kvsShaderAmbientTerm( Ka );
const float Id = kvsShaderDiffuseTerm( Kd, N, L );
const float Is = kvsShaderSpecularTerm( ks, S, R, V );
return ::Shade( color, Ia, Id, Is );
}
/*==========================================================================*/
inline float Shader::Lambert::attenuation( const kvs::Vector3f& vertex, const kvs::Vector3f& gradient ) const
{
// Light vector L and normal vector N.
const kvs::Vector3f L = ( light_position - vertex ).normalized();
const kvs::Vector3f N = gradient.normalized();
const float dd = kvs::Math::Max( N.dot( L ), 0.0f );
/* I = Ia + Id
*
* Ia = Ka (constant term)
* Id = Ip * Kd * cos(A) = Ip * Kd * ( L dot N )
*
* Ip : the intensity emitted from the light source.
*/
const float Ia = Ka;
const float Id = Kd * dd;
return Ia + Id;
}
/*==========================================================================*/
inline float Shader::BlinnPhong::attenuation( const kvs::Vector3f& vertex, const kvs::Vector3f& gradient ) const
{
// Camera vector C, light vector L, halfway vector H and normal vector N.
const kvs::Vector3f C = ( camera_position - vertex ).normalized();
const kvs::Vector3f L = ( light_position - vertex ).normalized();
const kvs::Vector3f H = ( C + L ).normalized();
const kvs::Vector3f N = gradient.normalized();
const float dd = kvs::Math::Max( N.dot( L ), 0.0f );
const float ds = kvs::Math::Max( N.dot( H ), 0.0f );
/* I = Ia + Id + Is
*
* Is = Ip * Ks * cos^s(B) = Ip * Ks * ( H dot N )^s
*/
const float Ia = Ka;
const float Id = Kd * dd;
const float Is = Ks * ::pow( ds, S );
return Ia + Id + Is;
}