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# PtexImporter/ptex/PtexSeparableKernel.h

    #ifndef PtexSeparableKernel_h
    #define PtexSeparableKernel_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"

    // Separable convolution kernel
    class PtexSeparableKernel : public Ptex {
     public:
        Res res;            // resolution that kernel was built for
        int u, v;           // uv offset within face data
        int uw, vw;         // kernel width
        double* ku;         // kernel weights in u
        double* kv;         // kernel weights in v
        static const int kmax = 10; // max kernel width
        double kubuff[kmax];
        double kvbuff[kmax];

        PtexSeparableKernel()
        : res(0), u(0), v(0), uw(0), vw(0), ku(kubuff), kv(kvbuff) {}

        PtexSeparableKernel(const PtexSeparableKernel& k)
        {
        set(k.res, k.u, k.v, k.uw, k.vw, k.ku, k.kv);
        }

        PtexSeparableKernel& operator= (const PtexSeparableKernel& k)
        {
        set(k.res, k.u, k.v, k.uw, k.vw, k.ku, k.kv);
        return *this;
        }

        void set(Res resVal,
             int uVal, int vVal,
             int uwVal, int vwVal,
             const double* kuVal, const double* kvVal)
        {
        assert(uwVal <= kmax && vwVal <= kmax);
        res = resVal;
        u = uVal;
        v = vVal;
        uw = uwVal;
        vw = vwVal;
        memcpy(kubuff, kuVal, sizeof(*ku)*uw);
        memcpy(kvbuff, kvVal, sizeof(*kv)*vw);
        ku = kubuff;
        kv = kvbuff;
        }

        void stripZeros()
        {
        while (ku[0] == 0) { ku++; u++; uw--; }
        while (ku[uw-1] == 0) { uw--; }
        while (kv[0] == 0) { kv++; v++; vw--; }
        while (kv[vw-1] == 0) { vw--; }
        assert(uw > 0 && vw > 0);
        }

        double weight() const
        {
        return accumulate(ku, uw) * accumulate(kv, vw);
        }

        void mergeL(BorderMode mode)
        {
        int w = -u;
        if (mode != m_black)
            ku[w] += accumulate(ku, w);
        ku += w;
        uw -= w;
        u = 0;
        }

        void mergeR(BorderMode mode)
        {
        int w = uw + u - res.u();
        double* kp = ku + uw - w;
        if (mode != m_black)
            kp[-1] += accumulate(kp, w);
        uw -= w;
        }

        void mergeB(BorderMode mode)
        {
        int w = -v;
        if (mode != m_black)
            kv[w] += accumulate(kv, w);
        kv += w;
        vw -= w;
        v = 0;
        }

        void mergeT(BorderMode mode)
        {
        int w = vw + v - res.v();
        double* kp = kv + vw - w;
        if (mode != m_black)
            kp[-1] += accumulate(kp, w);
        vw -= w;
        }

        void splitL(PtexSeparableKernel& k)
        {
        // split off left piece of width w into k
        int w = -u;

        if (w < uw) {
            // normal case - split off a portion
            //    res  u          v  uw vw  ku  kv
            k.set(res, res.u()-w, v, w, vw, ku, kv);

            // update local
            u = 0;
            uw -= w;
            ku += w;
        }
        else {
            // entire kernel is split off
            k = *this;
            k.u += res.u();
            u = 0; uw = 0;
        }
        }

        void splitR(PtexSeparableKernel& k)
        {
        // split off right piece of width w into k
        int w = u + uw - res.u();

        if (w < uw) {
            // normal case - split off a portion
            //    res  u  v  uw vw  ku           kv
            k.set(res, 0, v, w, vw, ku + uw - w, kv);

            // update local
            uw -= w;
        }
        else {
            // entire kernel is split off
            k = *this;
            k.u -= res.u();
            u = 0; uw = 0;
        }
        }

        void splitB(PtexSeparableKernel& k)
        {
        // split off bottom piece of width w into k
        int w = -v;
        if (w < vw) {
            // normal case - split off a portion
            //    res  u  v          uw vw  ku  kv
            k.set(res, u, res.v()-w, uw, w, ku, kv);

            // update local
            v = 0;
            vw -= w;
            kv += w;
        }
        else {
            // entire kernel is split off
            k = *this;
            k.v += res.v();
            v = 0; vw = 0;
        }
        }

        void splitT(PtexSeparableKernel& k)
        {
        // split off top piece of width w into k
        int w = v + vw - res.v();
        if (w < vw) {
            // normal case - split off a portion
            //    res  u  v  uw vw  ku  kv
            k.set(res, u, 0, uw, w, ku, kv + vw - w);

            // update local
            vw -= w;
        }
        else {
            // entire kernel is split off
            k = *this;
            k.v -= res.v();
            v = 0; vw = 0;
        }
        }

        void flipU()
        {
        u = res.u() - u - uw;
        std::reverse(ku, ku+uw);
        }

        void flipV()
        {
        v = res.v() - v - vw;
        std::reverse(kv, kv+vw);
        }

        void swapUV()
        {
        res.swapuv();
        std::swap(u, v);
        std::swap(uw, vw);
        std::swap(ku, kv);
        }

        void rotate(int rot)
        {
        // rotate kernel 'rot' steps ccw
        switch (rot & 3) {
        default: return;
        case 1: flipU(); swapUV(); break;
        case 2: flipU(); flipV(); break;
        case 3: flipV(); swapUV(); break;
        }
        }

        bool adjustMainToSubface(int eid)
        {
        // to adjust the kernel for the subface, we must adjust the res down and offset the uv coords
        // however, if the res is already zero, we must upres the kernel first
        if (res.ulog2 == 0) upresU();
        if (res.vlog2 == 0) upresV();

        if (res.ulog2 > 0) res.ulog2--;
        if (res.vlog2 > 0) res.vlog2--;

        // offset uv coords and determine whether target subface is the primary one
        bool primary = 0;
        int resu = res.u(), resv = res.v();
        switch (eid&3) {
        case e_bottom:
            primary = (u < resu);
            v -= resv;
            if (!primary) u -= resu;
            break;
        case e_right:
            primary = (v < resv);
            if (!primary) v -= resv;
            break;
        case e_top:
            primary = (u >= resu);
            if (primary) u -= resu;
            break;
        case e_left:
            primary = (v >= resv);
            u -= resu;
            if (primary) v -= resv;
            break;
        }
        return primary;
        }

        void adjustSubfaceToMain(int eid)
        {
        switch (eid&3) {
        case e_bottom: v += res.v(); break;
        case e_right:  break;
        case e_top:    u += res.u(); break;
        case e_left:   u += res.u(); v += res.v(); break;
        }
        res.ulog2++; res.vlog2++;
        }

        void downresU()
        {
        double* src = ku;
        double* dst = ku;

        // skip odd leading sample (if any)
        if (u & 1) {
            dst++;
            src++;
            uw--;
        }

        // combine even pairs
        for (int i = uw/2; i > 0; i--) {
            *dst++ = src[0] + src[1];
            src += 2;
        }

        // copy odd trailing sample (if any)
        if (uw & 1) {
            *dst++ = *src++;
        }

        // update state
        u /= 2;
        uw = int(dst - ku);
        res.ulog2--;
        }

        void downresV()
        {
        double* src = kv;
        double* dst = kv;

        // skip odd leading sample (if any)
        if (v & 1) {
            dst++;
            src++;
            vw--;
        }

        // combine even pairs
        for (int i = vw/2; i > 0; i--) {
            *dst++ = src[0] + src[1];
            src += 2;
        }

        // copy odd trailing sample (if any)
        if (vw & 1) {
            *dst++ = *src++;
        }

        // update state
        v /= 2;
        vw = int(dst - kv);
        res.vlog2--;
        }

        void upresU()
        {
        double* src = ku + uw-1;
        double* dst = ku + uw*2-2;
        for (int i = uw; i > 0; i--) {
            dst[0] = dst[1] = *src-- / 2;
            dst -=2;
        }
        uw *= 2;
        u *= 2;
        res.ulog2++;
        }

        void upresV()
        {
        double* src = kv + vw-1;
        double* dst = kv + vw*2-2;
        for (int i = vw; i > 0; i--) {
            dst[0] = dst[1] = *src-- / 2;
            dst -=2;
        }
        vw *= 2;
        v *= 2;
        res.vlog2++;
        }

        void makeSymmetric()
        {
        assert(u == 0 && v == 0);

        // downres higher-res dimension until equal
        if (res.ulog2 > res.vlog2) {
            do { downresU(); } while(res.ulog2 > res.vlog2);
        }
        else if (res.vlog2 > res.ulog2) {
            do { downresV(); } while (res.vlog2 > res.ulog2);
        }

        // check initial weight so we can preserve overall weight
        double initialWeight = weight();

        // truncate excess samples in longer dimension
        uw = vw = PtexUtils::min(uw, vw);

        // combine corresponding u and v samples
        double newWeight = 0;
        for (int i = 0; i < uw; i++) {
            ku[i] += kv[i];
            newWeight += ku[i];
        }

        // compensate for weight change by scaling v weights
        double scale = newWeight == 0 ? 1.0 : initialWeight / (newWeight * newWeight);
        for (int i = 0; i < uw; i++) kv[i] = ku[i] * scale;
        }

        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)
        {
        PtexUtils::applyConst(weight(), dst, data, dt, nChan);
        }

     private:
        typedef void (*ApplyFn)(PtexSeparableKernel& k, double* dst, void* data, int nChan, int nTxChan);
        typedef void (*ApplyConstFn)(double weight, double* dst, void* data, int nChan);
        static ApplyFn applyFunctions[40];
        static ApplyConstFn applyConstFunctions[20];
        static inline double accumulate(const double* p, int n)
        {
        double result = 0;
        for (const double* e = p + n; p != e; p++) result += *p;
        return result;
        }
    };

    #endif