射线和平面的相交性检测

参数情势的射线与平面相交公式可以参考3D数学基本：图形与游戏开发 p269

inline int cIntersectionSegmentPlane(const cVector3d& a_segmentPointA,
                                     const cVector3d& a_segmentPointB,
                                     const cVector3d& a_planePos,
                                     const cVector3d& a_planeNormal,
                                     cVector3d& a_collisionPoint,
                                     cVector3d& a_collisionNormal)
{
    cVector3d d = a_segmentPointB - a_segmentPointA;
    cVector3d p = a_segmentPointA;
    double length = d.length();

    // sanity check
    if (cZero(length)) 
    { 
        return (0);
    }

    // normalize d
    d.mul(1.0 / length);

    // compute intersection between segment and disk plane
    double c[2];
    double s[1];

    c[0] = a_planeNormal(0)*p(0) - a_planeNormal(0)*a_planePos(0) +
           a_planeNormal(1)*p(1) - a_planeNormal(1)*a_planePos(1) +
           a_planeNormal(2)*p(2) - a_planeNormal(2)*a_planePos(2);
    c[1] = a_planeNormal(0)*d(0) + a_planeNormal(1)*d(1) + a_planeNormal(2)*d(2);

    int num = cSolveLinear(c, s);

    if (num == 0)
    {
        return (0);
    }
    else
    {
        if ((s[0] >= 0.0) && (s[0] <= length))
        {
            a_collisionPoint = p + s[0] * d;
            if (cDot(a_planeNormal, cSub(a_segmentPointA, a_collisionPoint)) >= 0.0)
            {
                a_collisionNormal = a_planeNormal;
            }
            else
            {
                a_collisionNormal =-a_planeNormal;
            }
            return (1);
        }
        else
        {
            return (0);
        }
    }
}
inline int