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# PtexExtractor/ptex/PtexMitchellFilter.h

    #ifndef PtexMitchellFilter_h
    #define PtexMitchellFilter_h

    /*
    PTEX SOFTWARE
    Copyright 2009 Disney Enterprises, Inc.  All rights reserved

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are
    met:

      * Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.

      * Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in
        the documentation and/or other materials provided with the
        distribution.

      * The names "Disney", "Walt Disney Pictures", "Walt Disney Animation
        Studios" or the names of its contributors may NOT be used to
        endorse or promote products derived from this software without
        specific prior written permission from Walt Disney Pictures.

    Disclaimer: THIS SOFTWARE IS PROVIDED BY WALT DISNEY PICTURES AND
    CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
    BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS
    FOR A PARTICULAR PURPOSE, NONINFRINGEMENT AND TITLE ARE DISCLAIMED.
    IN NO EVENT SHALL WALT DISNEY PICTURES, THE COPYRIGHT HOLDER OR
    CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
    EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND BASED ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
    */

    #include <vector>
    #include "math.h"
    #include "Ptexture.h"
    #include "PtexFilterContext.h"
    #include "PtexFilterKernel.h"

    class PtexMitchellFilter : public PtexFilter, public Ptex
    {
     public:
        PtexMitchellFilter(PtexTexture* tx, float sharpness)
        : _tx(tx)
        {
        setSharpness(sharpness);
        }
        virtual void release() { delete this; }
        virtual void eval(float* result, int firstchan, int nchannels,
                  int faceid, float u, float v,
                  float uw1, float vw1, float uw2, float vw2,
                  float width, float blur);

     protected:
        struct Face {
        bool valid;     // true if face is valid
        bool blend;     // face needs blending due to insufficient res.
        int id;         // faceid
        int rotate;     // nsteps ccw face must be rotated to align w/ main
        Res res;        // resolution to filter face at (unrotated)
        operator bool() { return valid; }
        Face() : valid(0), blend(0) {}
        void set(int faceid, Res resval, int rotateval=0)
        {
            blend = 0;
            valid = 1;
            id = faceid;
            res = resval;
            rotate = rotateval&3;
            // swap u and v res if rotation is odd
            if (rotateval&1) res.swapuv();
        }
        void clampres(Res resval)
        {
            // clamp res to resval and set blend flag if < resval
            if (res.ulog2 > resval.ulog2) res.ulog2 = resval.ulog2;
            else if (res.ulog2 < resval.ulog2) blend = 1;
            if (res.vlog2 > resval.vlog2) res.vlog2 = resval.vlog2;
            else if (res.vlog2 < resval.vlog2) blend = 1;
        }
        void clear() { valid=0; blend=0; }
        };

        void setSharpness(float sharpness);
        void getNeighborhood(const FaceInfo& f);

        void computeWeights(double* kernel, double x1, double step, int size)
        {
        double m, x;
        const double* c = _filter;
        for (int i = 0; i < size; i++) {
            x = fabs(x1 + i*step);
            if (x < 1)      m = (c[0]*x + c[1])*x*x + c[2];
            else if (x < 2) m = ((c[3]*x + c[4])*x + c[5])*x + c[6];
            else m = 0;
            kernel[i] = m;
        }
        }

        void evalFaces(Res res, double weight, float uw, float vw);
        void evalFaces(Res res, double weight)
        {
        evalFaces(res, weight, 1.0f/res.u(), 1.0f/res.v());
        }
        void evalLargeDu(float du, float weight);
        void evalLargeDuFace(int faceid, int level, float weight);

        PtexTexture* _tx;       // the texture
        PtexFilterContext _ctx; // filter context

        bool _isConstant;       // true if neighborhood is constant
        bool _interior;     // true if corner point is an interior point
        double _ublend, _vblend;    // u,v edge blending weights (0=none, 1=full blend)
        Face _face, _uface, _vface; // main face and neighboring faces
        Face _cface;        // corner face (only valid if just one face)
        std::vector<Face> _cfaces;  // all faces around corner

        float _sharpness;       // current filter sharpness
        double _filter[7];      // filter coefficients for current sharpness
    };

    #endif