QwtSplineParametrization(3) Qwt User's Guide QwtSplineParametrization(3) NAME QwtSplineParametrization - Curve parametrization used for a spline interpolation. SYNOPSIS #include Public Types enum Type { ParameterX, ParameterY, ParameterUniform, ParameterChordal, ParameterCentripetal, ParameterManhattan } Parametrization type. Public Member Functions QwtSplineParametrization (int type) virtual ~QwtSplineParametrization () Destructor. int type () const virtual double valueIncrement (const QPointF &, const QPointF &) const Calculate the parameter value increment for 2 points. Static Public Member Functions static double valueIncrementX (const QPointF &, const QPointF &) Calculate the ParameterX value increment for 2 points. static double valueIncrementY (const QPointF &, const QPointF &) Calculate the ParameterY value increment for 2 points. static double valueIncrementUniform (const QPointF &, const QPointF &) Calculate the ParameterUniform value increment. static double valueIncrementChordal (const QPointF &, const QPointF &) Calculate the ParameterChordal value increment for 2 points. static double valueIncrementCentripetal (const QPointF &, const QPointF &) Calculate the ParameterCentripetal value increment for 2 points. static double valueIncrementManhattan (const QPointF &, const QPointF &) Calculate the ParameterManhattan value increment for 2 points. Detailed Description Curve parametrization used for a spline interpolation. Parametrization is the process of finding a parameter value for each curve point - usually related to some physical quantity ( distance, time ... ). Often accumulating the curve length is the intended way of parametrization, but as the interpolated curve is not known in advance an approximation needs to be used. The values are calculated by cumulating increments, that are provided by QwtSplineParametrization. As the curve parameters need to be montonically increasing, each increment need to be positive. o t[0] = 0; o t[i] = t[i-1] + valueIncrement( point[i-1], p[i] ); QwtSplineParametrization provides the most common used type of parametrizations and offers an interface to inject custom implementations. Note The most relevant types of parametrization are trying to provide an approximation of the curve length. See also QwtSpline::setParametrization() Definition at line 44 of file qwt_spline_parametrization.h. Member Enumeration Documentation enum QwtSplineParametrization::Type Parametrization type. Enumerator ParameterX No parametrization: t[i] = x[i] See also valueIncrementX() ParameterY No parametrization: t[i] = y[i] See also valueIncrementY() ParameterUniform Uniform parametrization: t[i] = i; A very fast parametrization, with good results, when the geometry of the control points is somehow 'equidistant'. F.e. when recording the position of a body, that is moving with constant speed every n seconds. See also valueIncrementUniform() ParameterChordal Parametrization using the chordal length between two control points The chordal length is the most commonly used approximation for the curve length. See also valueIncrementChordal() ParameterCentripetal Centripetal parametrization Based on the square root of the chordal length. Its name stems from the physical observations regarding the centripetal force, of a body moving along the curve. See also valueIncrementCentripetal() ParameterManhattan Parametrization using the manhattan length between two control points Approximating the curve length by the manhattan length is faster than the chordal length, but usually gives worse results. See also valueIncrementManhattan() Definition at line 48 of file qwt_spline_parametrization.h. Constructor & Destructor Documentation QwtSplineParametrization::QwtSplineParametrization (int type) [explicit] Constructor Parameters type Parametrization type See also type() Definition at line 17 of file qwt_spline_parametrization.cpp. Member Function Documentation int QwtSplineParametrization::type () const Returns Parametrization type Definition at line 72 of file qwt_spline_parametrization.cpp. double QwtSplineParametrization::valueIncrement (const QPointF & point1, const QPointF & point2) const [virtual] Calculate the parameter value increment for 2 points. Parameters point1 First point point2 Second point Returns Value increment Definition at line 35 of file qwt_spline_parametrization.cpp. double QwtSplineParametrization::valueIncrementCentripetal (const QPointF & point1, const QPointF & point2) [inline], [static] Calculate the ParameterCentripetal value increment for 2 points. Parameters point1 First point point2 Second point Returns The square root of a chordal increment Definition at line 196 of file qwt_spline_parametrization.h. double QwtSplineParametrization::valueIncrementChordal (const QPointF & point1, const QPointF & point2) [inline], [static] Calculate the ParameterChordal value increment for 2 points. Parameters point1 First point point2 Second point Returns qSqrt( dx * dx + dy * dy ); Definition at line 179 of file qwt_spline_parametrization.h. double QwtSplineParametrization::valueIncrementManhattan (const QPointF & point1, const QPointF & point2) [inline], [static] Calculate the ParameterManhattan value increment for 2 points. Parameters point1 First point point2 Second point Returns | point2.x() - point1.x() | + | point2.y() - point1.y() | Definition at line 210 of file qwt_spline_parametrization.h. double QwtSplineParametrization::valueIncrementUniform (const QPointF & point1, const QPointF & point2) [inline], [static] Calculate the ParameterUniform value increment. Parameters point1 First point point2 Second point Returns 1.0 Definition at line 162 of file qwt_spline_parametrization.h. double QwtSplineParametrization::valueIncrementX (const QPointF & point1, const QPointF & point2) [inline], [static] Calculate the ParameterX value increment for 2 points. Parameters point1 First point point2 Second point Returns point2.x() - point1.x(); Definition at line 134 of file qwt_spline_parametrization.h. double QwtSplineParametrization::valueIncrementY (const QPointF & point1, const QPointF & point2) [inline], [static] Calculate the ParameterY value increment for 2 points. Parameters point1 First point point2 Second point Returns point2.y() - point1.y(); Definition at line 148 of file qwt_spline_parametrization.h. Author Generated automatically by Doxygen for Qwt User's Guide from the source code. Version 6.2.0 Sun Jul 18 2021 QwtSplineParametrization(3)