UT/UT_PolySample.h

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/*
 * PROPRIETARY INFORMATION.  This software is proprietary to
 * Side Effects Software Inc., and is not to be reproduced,
 * transmitted, or disclosed in any way without written permission.
 *
 * Produced by:
 *      Jeff Lait
 *      Side Effects Software Inc
 *      477 Richmond Street West
 *      Toronto, Ontario
 *      Canada   M5V 3E7
 *      416-504-9876
 *
 * NAME:        UT_PolySample.h ( UT Library, C++)
 *
 * COMMENTS: This code comes from VRAY_Quad2d.h, and provies
 *           methods to sample two dimensional polygons.  Ie, given
 *           a point, find the "u v" coordinates of that point in
 *           the polygon.
 *           It currently only handles quads and tris.  Tris give
 *           barycentric coordinates, quads give bilinear interpolated
 *           coordinates.
 */

#ifndef __UT_PolySample__
#define __UT_PolySample__

#include "UT_API.h"
#include "UT_Vector2.h"

class UT_SampleQuad2D;

typedef int     (UT_SampleQuad2D::*UT_QuadSampleFunc)(double x, double y,
                                              float &u, float &v);

class UT_API UT_SampleSimpleTri2D {
public:
    float       u0, u1;
    float       v0, v1;
    float       Nxi;

    inline void init(float x0[2], float x1[2], float x2[2])
                {
                    u0 = x1[0] - x0[0]; v0 = x1[1] - x0[1];
                    u1 = x2[0] - x0[0]; v1 = x2[1] - x0[1];
                    Nxi = 1.0F/(u0*v1 - u1*v0);
                }
    inline void setVertices(fpreal x0, fpreal y0, fpreal x1, fpreal y1,
                            fpreal x2, fpreal y2)
                {
                    u0 = x1 - x0; v0 = y1 - y0;
                    u1 = x2 - x0; v1 = y2 - y0;
                    Nxi = 1.0F / (u0*v1 - u1*v0);
                }

    inline void initD0(float x0[2], float x2[2], fpreal dx, fpreal dy)
                {
                    u0 = dx; v0 = dy;
                    u1 = x2[0] - x0[0]; v1 = x2[1] - x0[1];
                    Nxi = 1/(u0*v1 - u1*v0);
                }

    inline int  sample(fpreal sx, fpreal sy, fpreal x0, fpreal y0, float &u, float &v)
                {
                    fpreal      tu, tv;
                    sx -= x0; sy -= y0;
                    tu = (sx*v1 - sy*u1) * Nxi;
                    if (tu >= 0 && tu <= 1) {
                        tv = (sy*u0 - sx*v0) * Nxi;
                        if (tv >= 0 && tu+tv <= 1) {
                            u = tu;
                            v = tv;
                            return 1;
                        }
                    }
                    return 0;
                 }
};

class UT_API UT_SampleTri2D {
public:
    int         isBackface() const      { return myBackface; }
    void        setVertices(fpreal x0, fpreal y0, fpreal x1, fpreal y1,
                            fpreal x2, fpreal y2)
                {
                    fpreal      dx, dy, z;
                    myX[0] = x0;
                    myX[1] = y0;
                    myTri.setVertices(x0, y0, x1, y1, x2, y2);
                    dx = myTri.v1; dy = -myTri.u1;
                    z = -(dx*x0 + dy*y0);
                    myBackface = dx*x1 + dy*y1 + z > 0;
                }
    int         sample(fpreal x, fpreal y, float &u, float &v)
                {
                    if (myTri.sample(x, y, myX[0], myX[1], u, v))
                    {
                        return 1;
                    }
                    return 0;
                }

private:
    UT_SampleSimpleTri2D         myTri;
    float                myX[2];
    int                  myBackface;
};

class UT_API UT_SampleQuad2D {
public:
    // Static init can be called once before sampling.  Please set up the point
    // positions before this is done...
    // If the polygon is large (in screen space), please set accurate to 1
    int         setVertices(fpreal x0, fpreal y0, fpreal x1, fpreal y1,
                            fpreal x2, fpreal y2, fpreal x3, fpreal y3)
                {
                    myXY[0][0] = x0; myXY[0][1] = y0;
                    myXY[1][0] = x1; myXY[1][1] = y1;
                    myXY[2][0] = x2; myXY[2][1] = y2;
                    myXY[3][0] = x3; myXY[3][1] = y3;
                    return init();
                }

    int          init();

    int          sample(double x, double y, float &u, float &v)
                 {
                     return (this->*mySampler)(x, y, u, v);
                 }

    // Call the sampler after the init.  See above for calling syntax
    int          isBackface() { return myBackface; }

private:
    // Trapezoidal sampling
    int          sampleTrap1(double x, double y, float &u, float &v);
    int          sampleTrap2(double x, double y, float &u, float &v);

    // Convex quadrilateral
    int          sampleQuad(double x, double y, float &u, float &v);
    // Concave quadrilateral
    int          sampleConcave(double x, double y, float &u, float &v);
    // Bowtie quad
    int          sampleBowtie(double x, double y, float &u, float &v);
    int          sampleGeneral(double x, double y, float &u, float &v);

    // Otherwise, only the following is needed
    float                myXY[4][2];

    UT_QuadSampleFunc    mySampler;
    UT_SampleSimpleTri2D myFirst;
    UT_SampleSimpleTri2D mySecond;
    UT_Vector2           myAB, myBC, myCD, myAD, myAE;
    float                myU, myV;
    int                  myBackface;
};

// This class actually performs bilinear sampling, which UT_SampleQuad2D
// does not seem to do.
class UT_API UT_BilinearSampleQuad2D {
public:
    // Static init can be called once before sampling.  Please set up the point
    // positions before this is done...
    void        setVertices(fpreal x0, fpreal y0, fpreal x1, fpreal y1,
                            fpreal x2, fpreal y2, fpreal x3, fpreal y3);

    // NOTE: The u & v here are returned using the Mantra style winding
    // of the polygon.  This is opposite of Houdini's winding, so if
    // this is to be used for evaluateInteriorPoint, one should
    // reverse the u & v values (or swap x1 & x2)
    int         sample(fpreal x, fpreal y, float &u, float &v);


private:
    int                  myBackface;
    int                  myFlipped;
    int                  myGeneral;
    float                mySBx, mySDx;

    float                myAx, myAy, myBx, myBy, myCx, myCy, myDx, myDy;
    float                myK, myIK, myL, myM;
};


#endif

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