Function splitAt

Engine/CoonsRegularization.cpp:584–673

} // findIntersection

static bool
splitAt(const BezierCPs &cps,
        double time,
        double t,
        std::list<BezierCPs>* ret)
{
    Point dir = dirVect(cps, time, t);

    if ( (dir.x != 0.) || (dir.y != 0.) ) {
        Point z = getPointAt(cps, time, t);
        Point zLeft = getLeftPointAt(cps, time, t);
        Point zRight = getRightPointAt(cps, time, t);
        Point q;
        q.x = z.x;
        q.y = z.y + dir.y;
        BezierCPPtr newPoint;
        int pointIdx = -1;
        findIntersection(cps, time, z, q, &newPoint, &pointIdx);
        assert( pointIdx >= 0 && pointIdx < (int)cps.size() );

        //Separate the original patch in 2 parts and call regularize again on each of them
        BezierCPs firstPart, secondPart;
        BezierCPs::const_iterator it = cps.begin();
        std::advance( it, std::ceil(t) );
        /*
           "it" is now pointing to the next control point after the split point
         */
        BezierCPs::const_iterator start = it;
        BezierCPs::const_iterator end = cps.begin();
        /*
           "end" is the control point before the intersection point
         */
        if (pointIdx > 0) {
            std::advance(end, pointIdx);
        }


        BezierCPPtr startingPoint = makeBezierCPFromPoint(z, zLeft, zRight);

        //Start by adding the split point (if it is not a control point)
        if (std::ceil(t) != t) {
            firstPart.push_back(startingPoint);
        }


        //Add all control points until we reach the point before the intersection point
        for (; it != end; ) {
            firstPart.push_back(*it);

            ++it;
            if ( it == cps.end() ) {
                it = cps.begin();
            }
        }
        firstPart.push_back(*end);
        //Add the intersection point
        firstPart.push_back(newPoint);