PerlinNoiseAlgorithm.h

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#ifndef VRECKO_NATURE_TERRAIN_PERLINNOISE_H
#define VRECKO_NATURE_TERRAIN_PERLINNOISE_H

#include "TerrainAlgorithm.h"
#include "../TerrainUtility.h"
#include <osg/Array>

namespace APNature
{
    class PerlinNoiseAlgorithm : public TerrainAlgorithm
    {
    private:

        int _permutationTable[514];
        osg::ref_ptr<osg::Vec2Array> _gradientsTable;

    public:

        PerlinNoiseAlgorithm(int width, int height);

        float GetNoise(float x, float y);
        
        float* GenerateNoiseTexture(float frequencyX, float frequencyY);

        float* GenerateCloudsTexture(std::size_t octaveCount, float persistence);

    private:

        void InitTables();

        static inline float EaseCurve(float t) { return (t * t) *  (3.0f - 2.0f * t); }

        inline osg::Vec2 GetGradient(int x, int y) { 
            return (*_gradientsTable)[ this->_permutationTable[ this->_permutationTable[ x ] + y ] ]; }

        static inline float InterpolationLinear(float from, float to, float x) { return from + x * (to - from); }

        static inline float InterpolationCosine(float from, float to, float x) { return from + 
            ((1.0f - cos(x * (float) osg::PI)) * 0.5f) * (to - from); }
    };

}

#endif