Interpolation.h

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Copyright (c) 2005-2009 David Williams

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#ifndef __PolyVox_Interpolation_H__
#define __PolyVox_Interpolation_H__

#include <cassert>

namespace PolyVox
{
    template <typename Type>
    Type lerp(
        const Type& v0,const Type& v1,
        const float x)
    {
        assert((x >= 0.0f) && (x <= 1.0f));

        //Interpolate along X
        Type v0_1 = v0 + x * (v1 - v0);

        return v0_1;
    }

    template <typename Type>
    Type bilerp(
        const Type& v00,const Type& v10,const Type& v01,const Type& v11,
        const float x, const float y)
    {
        assert((x >= 0.0f) && (y >= 0.0f) && 
            (x <= 1.0f) && (y <= 1.0f));

        // Linearly interpolate along x
        Type v00_10 = lerp(v00, v10, x);
        Type v01_11 = lerp(v01, v11, x);

        // And linearly interpolate the results along y
        Type v00_10__v01_11 = lerp(v00_10, v01_11, y);

        return v00_10__v01_11;
    }

    template <typename Type>
    Type trilerp(
        const Type& v000,const Type& v100,const Type& v010,const Type& v110,
        const Type& v001,const Type& v101,const Type& v011,const Type& v111,
        const float x, const float y, const float z)
    {
        assert((x >= 0.0f) && (y >= 0.0f) && (z >= 0.0f) && 
            (x <= 1.0f) && (y <= 1.0f) && (z <= 1.0f));

        // Bilinearly interpolate along Y
        Type v000_v100__v010_v110 = bilerp(v000, v100, v010, v110, x, y);
        Type v001_v101__v011_v111 = bilerp(v001, v101, v011, v111, x, y);

        // And linearly interpolate the results along z
        Type v000_v100__v010_v110____v001_v101__v011_v111 = lerp(v000_v100__v010_v110, v001_v101__v011_v111, z);
            
        return v000_v100__v010_v110____v001_v101__v011_v111;
    }
}

#endif //__PolyVox_Interpolation_H__