TBlackmanHarris2D.h

Go to the documentation of this file.

#pragma once
 
#include "Math/Function/TMathFunction2D.h"
#include "Math/constant.h"
 
#include <Common/assertion.h>
 
#include <cmath>
 
namespace ph::math
{
 
template<typename Value>
class TBlackmanHarris2D : public TMathFunction2D<Value>
{
public:
    explicit TBlackmanHarris2D(Value radius);
 
    Value evaluate(Value x, Value y) const override;
 
private:
    Value m_reciRadius;
 
    Value blackmanHarris1D(Value n) const;
};
 
template<typename Value>
inline TBlackmanHarris2D<Value>::TBlackmanHarris2D(const Value radius)
    : m_reciRadius(radius > Value(0) ? Value(1) / radius : Value(0))
{
    PH_ASSERT(radius > Value(0));
}
 
template<typename Value>
inline Value TBlackmanHarris2D<Value>::evaluate(const Value x, const Value y) const
{
    const Value nx = (x * m_reciRadius + Value(1.0)) * Value(0.5);
    const Value ny = (y * m_reciRadius + Value(1.0)) * Value(0.5);
 
    return blackmanHarris1D(nx) * blackmanHarris1D(ny);
}
 
template<typename Value>
inline Value TBlackmanHarris2D<Value>::blackmanHarris1D(const Value n) const
{
    return 
          Value(0.35875)
        - Value(0.48829) * std::cos(Value(2.0) * constant::pi<Value> * n)
        + Value(0.14128) * std::cos(Value(4.0) * constant::pi<Value> * n)
        - Value(0.01174) * std::cos(Value(6.0) * constant::pi<Value> * n);
    //          ^^^^^^^
    // NOTE: Originally this coefficient is 0.01168, we modified it like how
    //       appleseed renderer did to make it evaluate to 0 at boundaries.
}
 
}// end namespace ph::math