MRBezier.h

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#pragma once
 
#include "MRMeshFwd.h"
#include "MRVectorTraits.h"
#include <array>
 
namespace MR
{
 
template <typename V>
struct CubicBezierCurve
{
    using VTraits = VectorTraits<V>;
    using T = typename VTraits::BaseType;
    static constexpr int elements = VTraits::size;
 
    V p[4];
 
    V getPoint( T t ) const;
 
    static std::array<T, 4> getWeights( T t );
};
 
template <typename V>
inline V CubicBezierCurve<V>::getPoint( T t ) const
{
    // De Casteljau's algorithm
    V q[3];
    for ( int i = 0; i < 3; ++i )
        q[i] = lerp( p[i], p[i+1], t );
 
    V r[2];
    for ( int i = 0; i < 2; ++i )
        r[i] = lerp( q[i], q[i+1], t );
 
    return lerp( r[0], r[1], t );
}
 
template <typename V>
inline auto CubicBezierCurve<V>::getWeights( T t ) -> std::array<T, 4>
{
    T s = 1 - t;
    std::array<T, 4> w =
    {
            s * s * s,
        3 * s * s * t,
        3 * s * t * t
    };
    w[3] = 1 - w[0] - w[1] - w[2];
    return w;
}
 
} //namespace MR