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# PtexExtractor/ptex/PtexTriangleKernel.h

    #ifndef PtexTriangleKernel_h
    #define PtexTriangleKernel_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 <assert.h>
    #include <algorithm>
    #include <numeric>
    #include "Ptexture.h"
    #include "PtexUtils.h"

    // kernel width as a multiple of filter width (should be between 3 and 4)
    // for values below 3, the gaussian is not close to zero and a contour will be formed
    // larger values are more expensive (proportional to width-squared)
    static const float PtexTriangleKernelWidth = 3.5;

    class PtexTriangleKernelIter : public Ptex {
     public:
        int rowlen;         // row length (in u)
        double u, v;        // uv center in texels
        int u1, v1, w1;     // uvw lower bounds
        int u2, v2, w2;     // uvw upper bounds
        double A,B,C;       // ellipse coefficients (F = 1)
        bool valid;         // footprint is valid (non-empty)
        double wscale;      // amount to scale weights by (proportional to texel area)
        double weight;      // accumulated weight

        void apply(double* dst, void* data, DataType dt, int nChan, int nTxChan)
        {
        // dispatch specialized apply function
        ApplyFn fn = applyFunctions[(nChan!=nTxChan)*20 + ((unsigned)nChan<=4)*nChan*4 + dt];
        fn(*this, dst, data, nChan, nTxChan);
        }

        void applyConst(double* dst, void* data, DataType dt, int nChan);

     private:

        typedef void (*ApplyFn)(PtexTriangleKernelIter& k, double* dst, void* data, int nChan, int nTxChan);
        static ApplyFn applyFunctions[40];
    };

    class PtexTriangleKernel : public Ptex {
     public:
        Res res;            // desired resolution
        double u, v;        // uv filter center
        double u1, v1, w1;      // uvw lower bounds
        double u2, v2, w2;      // uvw upper bounds
        double A,B,C;       // ellipse coefficients (F = A*C-B*B/4)

        void set(Res resVal, double uVal, double vVal,
             double u1Val, double v1Val, double w1Val,
             double u2Val, double v2Val, double w2Val,
             double AVal, double BVal, double CVal)
        {
        res = resVal;
        u = uVal; v = vVal;
        u1 = u1Val; v1 = v1Val; w1 = w1Val;
        u2 = u2Val; v2 = v2Val; w2 = w2Val;
        A = AVal; B = BVal; C = CVal;
        }

        void set(double uVal, double vVal,
             double u1Val, double v1Val, double w1Val,
             double u2Val, double v2Val, double w2Val)
        {
        u = uVal; v = vVal;
        u1 = u1Val; v1 = v1Val; w1 = w1Val;
        u2 = u2Val; v2 = v2Val; w2 = w2Val;
        }

        void setABC(double AVal, double BVal, double CVal)
        {
        A = AVal; B = BVal; C = CVal;
        }

        void splitU(PtexTriangleKernel& ka)
        {
        ka = *this;
        u1 = 0;
        ka.u2 = 0;
        }

        void splitV(PtexTriangleKernel& ka)
        {
        ka = *this;
        v1 = 0;
        ka.v2 = 0;
        }

        void splitW(PtexTriangleKernel& ka)
        {
        ka = *this;
        w1 = 0;
        ka.w2 = 0;
        }

        void rotate1()
        {
        // rotate ellipse where u'=w, v'=u, w'=v
        // (derived by converting to Barycentric form, rotating, and converting back)
        setABC(C, 2*C-B, A+C-B);
        }

        void rotate2()
        {
        // rotate ellipse where u'=v, v'=w, w'=u
        // (derived by converting to Barycentric form, rotating, and converting back)
        setABC(A+C-B, 2*A-B, A);
        }

        void reorient(int eid, int aeid)
        {
        double w = 1-u-v;

    #define C(eid, aeid) (eid*3 + aeid)
        switch (C(eid, aeid)) {
        case C(0, 0): set(1-u,  -v, 1-u2,  -v2, 1-w2, 1-u1,  -v1, 1-w1); break;
        case C(0, 1): set(1-w, 1-u, 1-w2, 1-u2,  -v2, 1-w1, 1-u1,  -v1); rotate1(); break;
        case C(0, 2): set( -v, 1-w,  -v2, 1-w2, 1-u2,  -v1, 1-w1, 1-u1); rotate2(); break;

        case C(1, 0): set(1-v,  -w, 1-v2,  -w2, 1-u2, 1-v1,  -w1, 1-u1); rotate2(); break;
        case C(1, 1): set(1-u, 1-v, 1-u2, 1-v2,  -w2, 1-u1, 1-v1,  -w1); break;
        case C(1, 2): set( -w, 1-u,  -w2, 1-u2, 1-v2,  -w1, 1-u1, 1-v1); rotate1(); break;

        case C(2, 0): set(1-w,  -u, 1-w2,  -u2, 1-v2, 1-w1,  -u1, 1-v1); rotate1(); break;
        case C(2, 1): set(1-v, 1-w, 1-v2, 1-w2,  -u2, 1-v1, 1-w1,  -u1); rotate2(); break;
        case C(2, 2): set( -u, 1-v,  -u2, 1-v2, 1-w2,  -u1, 1-v1, 1-w1); break;
    #undef C
        }
        }

        void clampRes(Res fres)
        {
        res.ulog2 = PtexUtils::min(res.ulog2, fres.ulog2);
        res.vlog2 = res.ulog2;
        }

        void clampExtent()
        {
        u1 = PtexUtils::max(u1, 0.0);
        v1 = PtexUtils::max(v1, 0.0);
        w1 = PtexUtils::max(w1, 0.0);
        u2 = PtexUtils::min(u2, 1-(v1+w1));
        v2 = PtexUtils::min(v2, 1-(w1+u1));
        w2 = PtexUtils::min(w2, 1-(u1+v1));
        }

        void getIterators(PtexTriangleKernelIter& ke, PtexTriangleKernelIter& ko)
        {
        int resu = res.u();

        // normalize coefficients for texel units
        double Finv = 1.0/(resu*resu*(A*C - 0.25 * B * B));
        double Ak = A*Finv, Bk = B*Finv, Ck = C*Finv;

        // build even iterator
        ke.rowlen = resu;
        ke.wscale = 1.0/(resu*resu);
        double scale = ke.rowlen;
        ke.u = u * scale - 1/3.0;
        ke.v = v * scale - 1/3.0;
        ke.u1 = int(ceil(u1 * scale - 1/3.0));
        ke.v1 = int(ceil(v1 * scale - 1/3.0));
        ke.w1 = int(ceil(w1 * scale - 1/3.0));
        ke.u2 = int(ceil(u2 * scale - 1/3.0));
        ke.v2 = int(ceil(v2 * scale - 1/3.0));
        ke.w2 = int(ceil(w2 * scale - 1/3.0));
        ke.A = Ak; ke.B = Bk; ke.C = Ck;
        ke.valid = (ke.u2 > ke.u1 && ke.v2 > ke.v1 && ke.w2 > ke.w1);
        ke.weight = 0;

        // build odd iterator: flip kernel across diagonal (u = 1-v, v = 1-u, w = -w)
        ko.rowlen = ke.rowlen;
        ko.wscale = ke.wscale;
        ko.u = (1-v) * scale - 1/3.0;
        ko.v = (1-u) * scale - 1/3.0;
        ko.u1 = int(ceil((1-v2) * scale - 1/3.0));
        ko.v1 = int(ceil((1-u2) * scale - 1/3.0));
        ko.w1 = int(ceil(( -w2) * scale - 1/3.0));
        ko.u2 = int(ceil((1-v1) * scale - 1/3.0));
        ko.v2 = int(ceil((1-u1) * scale - 1/3.0));
        ko.w2 = int(ceil(( -w1) * scale - 1/3.0));
        ko.A = Ck; ko.B = Bk; ko.C = Ak;
        ko.valid = (ko.u2 > ko.u1 && ko.v2 > ko.v1 && ko.w2 > ko.w1);
        ko.weight = 0;
        }
    };

    #endif