PtexFilters.cpp

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#include "PtexPlatform.h"
#include "Ptexture.h"
#include "PtexSeparableFilter.h"
#include "PtexSeparableKernel.h"
#include "PtexTriangleFilter.h"
 
PTEX_NAMESPACE_BEGIN
 
class PtexPointFilter : public PtexFilter
{
 public:
    PtexPointFilter(PtexTexture* tx) : _tx(tx) {}
    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*/)
    {
        if (!_tx || nchannels <= 0) return;
        if (faceid < 0 || faceid >= _tx->numFaces()) return;
        const FaceInfo& f = _tx->getFaceInfo(faceid);
        int resu = f.res.u(), resv = f.res.v();
        int ui = PtexUtils::clamp(int(u*(float)resu), 0, resu-1);
        int vi = PtexUtils::clamp(int(v*(float)resv), 0, resv-1);
        _tx->getPixel(faceid, ui, vi, result, firstchan, nchannels);
    }
 
 private:
    PtexTexture* _tx;
};
 
 
class PtexPointFilterTri : public PtexFilter
{
 public:
    PtexPointFilterTri(PtexTexture* tx) : _tx(tx) {}
    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*/)
    {
        if (!_tx || nchannels <= 0) return;
        if (faceid < 0 || faceid >= _tx->numFaces()) return;
        const FaceInfo& f = _tx->getFaceInfo(faceid);
        int res = f.res.u();
        int resm1 = res - 1;
        float ut = u * (float)res, vt = v * (float)res;
        int ui = PtexUtils::clamp(int(ut), 0, resm1);
        int vi = PtexUtils::clamp(int(vt), 0, resm1);
        float uf = ut - (float)ui, vf = vt - (float)vi;
 
        if (uf + vf <= 1.0f) {
            // "even" triangles are stored in lower-left half-texture
            _tx->getPixel(faceid, ui, vi, result, firstchan, nchannels);
        }
        else {
            // "odd" triangles are stored in upper-right half-texture
            _tx->getPixel(faceid, resm1-vi, resm1-ui, result, firstchan, nchannels);
        }
    }
 
 private:
    PtexTexture* _tx;
};
 
 
class PtexWidth4Filter : public PtexSeparableFilter
{
 public:
    typedef float KernelFn(float x, const float* c);
 
    PtexWidth4Filter(PtexTexture* tx, const PtexFilter::Options& opts, KernelFn k, const float* c = 0)
        : PtexSeparableFilter(tx, opts), _k(k), _c(c) {}
 
    virtual void buildKernel(PtexSeparableKernel& k, float u, float v, float uw, float vw,
                             Res faceRes)
    {
        buildKernelAxis(k.res.ulog2, k.u, k.uw, k.ku, u, uw, faceRes.ulog2);
        buildKernelAxis(k.res.vlog2, k.v, k.vw, k.kv, v, vw, faceRes.vlog2);
    }
 
 private:
 
    float blur(float x)
    {
        // 2-unit (x in -1..1) cubic hermite kernel
        // this produces a blur roughly 1.5 times that of the 4-unit b-spline kernel
        x = PtexUtils::abs(x);
        return x < 1.0f ? (2.0f*x-3.0f)*x*x+1.0f : 0.0f;
    }
 
    void buildKernelAxis(int8_t& k_ureslog2, int& k_u, int& k_uw, float* ku,
                         float u, float uw, int f_ureslog2)
    {
        // build 1 axis (note: "u" labels may repesent either u or v axis)
 
        // clamp filter width to no smaller than a texel
        uw = PtexUtils::max(uw, PtexUtils::reciprocalPow2(f_ureslog2));
 
        // compute desired texture res based on filter width
        k_ureslog2 = (int8_t)PtexUtils::calcResFromWidth(uw);
        int resu = 1 << k_ureslog2;
        float uwlo = 1.0f/(float)resu; // smallest filter width for this res
 
        // compute lerp weights (amount to blend towards next-lower res)
        float lerp2 = _options.lerp ? (uw-uwlo)/uwlo : 0;
        float lerp1 = 1.0f-lerp2;
 
        // adjust for large filter widths
        if (uw >= .25f) {
            if (uw < .5f) {
                k_ureslog2 = 2;
                float upix = u * 4.0f - 0.5f;
                int u1 = int(PtexUtils::ceil(upix - 2)), u2 = int(PtexUtils::ceil(upix + 2));
                u1 = u1 & ~1;       // round down to even pair
                u2 = (u2 + 1) & ~1; // round up to even pair
                k_u = u1;
                k_uw = u2-u1;
                float x1 = (float)u1-upix;
                for (int i = 0; i < k_uw; i+=2) {
                    float xa = x1 + (float)i, xb = xa + 1.0f, xc = (xa+xb)*0.25f;
                    // spread the filter gradually to approach the next-lower-res width
                    // at uw = .5, s = 1.0; at uw = 1, s = 0.8
                    float s = 1.0f/(uw + .75f);
                    float ka = _k(xa, _c), kb = _k(xb, _c), kc = blur(xc*s);
                    ku[i] = ka * lerp1 + kc * lerp2;
                    ku[i+1] = kb * lerp1 + kc * lerp2;
                }
                return;
            }
            else if (uw < 1) {
                k_ureslog2 = 1;
                float upix = u * 2.0f - 0.5f;
                k_u = int(PtexUtils::floor(u - .5f))*2;
                k_uw = 4;
                float x1 = (float)k_u-upix;
                for (int i = 0; i < k_uw; i+=2) {
                    float xa = x1 + (float)i, xb = xa + 1.0f, xc = (xa+xb)*0.5f;
                    // spread the filter gradually to approach the next-lower-res width
                    // at uw = .5, s = .8; at uw = 1, s = 0.5
                    float s = 1.0f/(uw*1.5f + .5f);
                    float ka = blur(xa*s), kb = blur(xb*s), kc = blur(xc*s);
                    ku[i] = ka * lerp1 + kc * lerp2;
                    ku[i+1] = kb * lerp1 + kc * lerp2;
                }
                return;
            }
            else {
                // use res 0 (1 texel per face) w/ no lerping
                // (future: use face-blended values for filter > 2)
                k_ureslog2 = 0;
                float upix = u - .5f;
                k_uw = 2;
                float ui = PtexUtils::floor(upix);
                k_u = int(ui);
                ku[0] = blur(upix-ui);
                ku[1] = 1-ku[0];
                return;
            }
        }
 
        // convert from normalized coords to pixel coords
        float upix = u * (float)resu - 0.5f;
        float uwpix = uw * (float)resu;
 
        // find integer pixel extent: [u,v] +/- [2*uw,2*vw]
        // (kernel width is 4 times filter width)
        float dupix = 2.0f*uwpix;
        int u1 = int(PtexUtils::ceil(upix - dupix)), u2 = int(PtexUtils::ceil(upix + dupix));
 
        if (lerp2) {
            // lerp kernel weights towards next-lower res
            // extend kernel width to cover even pairs
            u1 = u1 & ~1;
            u2 = (u2 + 1) & ~1;
            k_u = u1;
            k_uw = u2-u1;
 
            // compute kernel weights
            float step = 1.0f/uwpix, x1 = ((float)u1-upix)*(float)step;
            for (int i = 0; i < k_uw; i+=2) {
                float xa = x1 + (float)i*step, xb = xa + step, xc = (xa+xb)*0.5f;
                float ka = _k(xa, _c), kb = _k(xb, _c), kc = _k(xc, _c);
                ku[i] = ka * lerp1 + kc * lerp2;
                ku[i+1] = kb * lerp1 + kc * lerp2;
            }
        }
        else {
            k_u = u1;
            k_uw = u2-u1;
            // compute kernel weights
            float x1 = ((float)u1-upix)/uwpix, step = 1.0f/uwpix;
            for (int i = 0; i < k_uw; i++) ku[i] = _k(x1 + (float)i*step, _c);
        }
    }
 
    KernelFn* _k;               // kernel function
    const float* _c;            // kernel coefficients (if any)
};
 
 
class PtexBicubicFilter : public PtexWidth4Filter
{
 public:
    PtexBicubicFilter(PtexTexture* tx, const PtexFilter::Options& opts, float sharpness)
        : PtexWidth4Filter(tx, opts, kernelFn, _coeffs)
    {
        // compute Cubic filter coefficients:
        // abs(x) < 1:
        //   1/6 * ((12 - 9*B - 6*C)*x^3 + (-18 + 12*B + 6*C)*x^2 + (6 - 2*B))
        //   == c[0]*x^3 + c[1]*x^2 + c[2]
        // abs(x) < 2:
        //   1/6 * ((-B - 6*C)*x^3 + (6*B + 30*C)*x^2 + (-12*B - 48*C)*x + (8*B + 24*C))
        //   == c[3]*x^3 + c[4]*x^2 + c[5]*x + c[6]
        // else: 0
 
        float B = 1.0f - sharpness; // choose C = (1-B)/2
        _coeffs[0] = 1.5f - B;
        _coeffs[1] = 1.5f * B - 2.5f;
        _coeffs[2] = 1.0f - float(1.0/3.0) * B;
        _coeffs[3] = float(1.0/3.0) * B - 0.5f;
        _coeffs[4] = 2.5f - 1.5f * B;
        _coeffs[5] = 2.0f * B - 4.0f;
        _coeffs[6] = 2.0f - float(2.0/3.0) * B;
    }
 
 private:
    static float kernelFn(float x, const float* c)
    {
        x = PtexUtils::abs(x);
        if (x < 1.0f)      return (c[0]*x + c[1])*x*x + c[2];
        else if (x < 2.0f) return ((c[3]*x + c[4])*x + c[5])*x + c[6];
        else               return 0.0f;
    }
 
    float _coeffs[7]; // filter coefficients for current sharpness
};
 
 
 
class PtexGaussianFilter : public PtexWidth4Filter
{
 public:
    PtexGaussianFilter(PtexTexture* tx, const PtexFilter::Options& opts)
        : PtexWidth4Filter(tx, opts, kernelFn) {}
 
 private:
    static float kernelFn(float x, const float*)
    {
        return (float)exp(-2.0f*x*x);
    }
};
 
 
 
class PtexBoxFilter : public PtexSeparableFilter
{
 public:
    PtexBoxFilter(PtexTexture* tx, const PtexFilter::Options& opts)
        : PtexSeparableFilter(tx, opts) {}
 
 protected:
    virtual void buildKernel(PtexSeparableKernel& k, float u, float v, float uw, float vw,
                             Res faceRes)
    {
        // clamp filter width to no larger than 1.0
        uw = PtexUtils::min(uw, 1.0f);
        vw = PtexUtils::min(vw, 1.0f);
 
        // clamp filter width to no smaller than a texel
        uw = PtexUtils::max(uw, PtexUtils::reciprocalPow2(faceRes.ulog2));
        vw = PtexUtils::max(vw, PtexUtils::reciprocalPow2(faceRes.vlog2));
 
        // compute desired texture res based on filter width
        uint8_t ureslog2 = (uint8_t)PtexUtils::calcResFromWidth(uw);
        uint8_t vreslog2 = (uint8_t)PtexUtils::calcResFromWidth(vw);
        Res res(ureslog2, vreslog2);
        k.res = res;
 
        // convert from normalized coords to pixel coords
        u = u * (float)k.res.u();
        v = v * (float)k.res.v();
        uw *= (float)k.res.u();
        vw *= (float)k.res.v();
 
        // find integer pixel extent: [u,v] +/- [uw/2,vw/2]
        // (box is 1 unit wide for a 1 unit filter period)
        float u1 = u - 0.5f*uw, u2 = u + 0.5f*uw;
        float v1 = v - 0.5f*vw, v2 = v + 0.5f*vw;
        float u1floor = PtexUtils::floor(u1), u2ceil = PtexUtils::ceil(u2);
        float v1floor = PtexUtils::floor(v1), v2ceil = PtexUtils::ceil(v2);
        k.u = int(u1floor);
        k.v = int(v1floor);
        k.uw = int(u2ceil)-k.u;
        k.vw = int(v2ceil)-k.v;
 
        // compute kernel weights along u and v directions
        computeWeights(k.ku, k.uw, 1.0f-(u1-u1floor), 1.0f-(u2ceil-u2));
        computeWeights(k.kv, k.vw, 1.0f-(v1-v1floor), 1.0f-(v2ceil-v2));
    }
 
 private:
    void computeWeights(float* kernel, int size, float f1, float f2)
    {
        assert(size >= 1 && size <= 3);
 
        if (size == 1) {
            kernel[0] = f1 + f2 - 1.0f;
        }
        else {
            kernel[0] = f1;
            for (int i = 1; i < size-1; i++) kernel[i] = 1.0f;
            kernel[size-1] = f2;
        }
    }
};
 
 
class PtexBilinearFilter : public PtexSeparableFilter
{
 public:
    PtexBilinearFilter(PtexTexture* tx, const PtexFilter::Options& opts)
        : PtexSeparableFilter(tx, opts) {}
 
 protected:
    virtual void buildKernel(PtexSeparableKernel& k, float u, float v, float uw, float vw,
                             Res faceRes)
    {
        // clamp filter width to no larger than 1.0
        uw = PtexUtils::min(uw, 1.0f);
        vw = PtexUtils::min(vw, 1.0f);
 
        // clamp filter width to no smaller than a texel
        uw = PtexUtils::max(uw, PtexUtils::reciprocalPow2(faceRes.ulog2));
        vw = PtexUtils::max(vw, PtexUtils::reciprocalPow2(faceRes.vlog2));
 
        uint8_t ureslog2 = (uint8_t)PtexUtils::calcResFromWidth(uw);
        uint8_t vreslog2 = (uint8_t)PtexUtils::calcResFromWidth(vw);
        Res res(ureslog2, vreslog2);
        k.res = res;
 
        // convert from normalized coords to pixel coords
        float upix = u * (float)k.res.u() - 0.5f;
        float vpix = v * (float)k.res.v() - 0.5f;
 
        float ufloor = PtexUtils::floor(upix);
        float vfloor = PtexUtils::floor(vpix);
        k.u = int(ufloor);
        k.v = int(vfloor);
        k.uw = 2;
        k.vw = 2;
 
        // compute kernel weights
        float ufrac = upix-ufloor, vfrac = vpix-vfloor;
        k.ku[0] = 1.0f - ufrac;
        k.ku[1] = ufrac;
        k.kv[0] = 1.0f - vfrac;
        k.kv[1] = vfrac;
    }
};
 
 
PtexFilter* PtexFilter::getFilter(PtexTexture* tex, const PtexFilter::Options& opts)
{
    switch (tex->meshType()) {
    case Ptex::mt_quad:
        switch (opts.filter) {
        case f_point:       return new PtexPointFilter(tex);
        case f_bilinear:    return new PtexBilinearFilter(tex, opts);
        default:
        case f_box:         return new PtexBoxFilter(tex, opts);
        case f_gaussian:    return new PtexGaussianFilter(tex, opts);
        case f_bicubic:     return new PtexBicubicFilter(tex, opts, opts.sharpness);
        case f_bspline:     return new PtexBicubicFilter(tex, opts, 0.f);
        case f_catmullrom:  return new PtexBicubicFilter(tex, opts, 1.f);
        case f_mitchell:    return new PtexBicubicFilter(tex, opts, 2.f/3.f);
        }
        break;
 
    case Ptex::mt_triangle:
        switch (opts.filter) {
        case f_point:       return new PtexPointFilterTri(tex);
        default:            return new PtexTriangleFilter(tex, opts);
        }
        break;
    }
    return 0;
}
 
PTEX_NAMESPACE_END