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Usage
Defines a piecewise function mapping. This mapping allows
the addition of control points, and allows the user to
control the function between the control points. A piecewise
hermite curve is used between control points, based on the
sharpness and midpoint parameters. A sharpness of 0 yields a
piecewise linear function and a sharpness of 1 yields a
piecewise constant function. The midpoint is the normalized
distance between control points at which the curve reaches
the median Y value. The midpoint and sharpness values
specified when adding a node are used to control the
transition to the next node (the last node's values are
ignored) Outside the range of nodes, the values are 0 if
Clamping is off, or the nearest node point if Clamping is
on. Using the legacy methods for adding points (which do not
have Sharpness and Midpoint parameters) will default to
Midpoint = 0.5 (halfway between the control points) and
Sharpness = 0.0 (linear).
To create an instance of class vtkPiecewiseFunction, simply
invoke its constructor as follows
obj = vtkPiecewiseFunction
Methods
The class vtkPiecewiseFunction has several methods that can
be used. They are listed below. Note that the documentation
is translated automatically from the VTK sources, and may
not be completely intelligible. When in doubt, consult the
VTK website. In the methods listed below, obj is an instance
of the vtkPiecewiseFunction class.
* string = obj.GetClassName ()
* int = obj.IsA (string name)
* vtkPiecewiseFunction = obj.NewInstance ()
* vtkPiecewiseFunction = obj.SafeDownCast (vtkObject o)
* obj.DeepCopy (vtkDataObject f)
* obj.ShallowCopy (vtkDataObject f)
* int = obj.GetDataObjectType () - Return what type of
dataset this is.
* int = obj.GetSize () - Get the number of points used to
specify the function
* int = obj.AddPoint (double x, double y) - Add/Remove
points to/from the function. If a duplicate point is added
then the function value is changed at that location.
Return the index of the point (0 based), or -1 on error.
* int = obj.AddPoint (double x, double y, double midpoint,
double sharpness) - Add/Remove points to/from the
function. If a duplicate point is added then the function
value is changed at that location. Return the index of the
point (0 based), or -1 on error.
* int = obj.RemovePoint (double x) - Add/Remove points to/
from the function. If a duplicate point is added then the
function value is changed at that location. Return the
index of the point (0 based), or -1 on error.
* obj.RemoveAllPoints () - Removes all points from the
function.
* obj.AddSegment (double x1, double y1, double x2, double
y2) - Add a line segment to the function. All points
defined between the two points specified are removed from
the function. This is a legacy method that does not allow
the specification of the sharpness and midpoint values for
the two nodes.
* double = obj.GetValue (double x) - Returns the value of
the function at the specified location using the specified
interpolation.
* int = obj.GetNodeValue (int index, double val[4]) - For
the node specified by index, set/get the location (X),
value (Y), midpoint, and sharpness values at the node.
* int = obj.SetNodeValue (int index, double val[4]) - For
the node specified by index, set/get the location (X),
value (Y), midpoint, and sharpness values at the node.
* obj.FillFromDataPointer (int , double ) - Returns a
pointer to the data stored in the table. Fills from a
pointer to data stored in a similar table. These are
legacy methods which will be maintained for compatibility
- however, note that the vtkPiecewiseFunction no longer
stores the nodes in a double array internally.
* double = obj. GetRange () - Returns the min and max node
locations of the function.
* int = obj.AdjustRange (double range[2]) - Remove all
points out of the new range, and make sure there is a
point at each end of that range. Return 1 on success, 0
otherwise.
* obj.GetTable (double x1, double x2, int size, float table,
int stride) - Fills in an array of function values
evaluated at regular intervals. Parameter "stride" is used
to step through the output "table".
* obj.GetTable (double x1, double x2, int size, double
table, int stride) - Fills in an array of function values
evaluated at regular intervals. Parameter "stride" is used
to step through the output "table".
* obj.BuildFunctionFromTable (double x1, double x2, int
size, double table, int stride) - Constructs a piecewise
function from a table. Function range is is set to [x1,
x2], function size is set to size, and function points are
regularly spaced between x1 and x2. Parameter "stride" is
is step through the input table.
* obj.SetClamping (int ) - When zero range clamping is Off,
GetValue() returns 0.0 when a value is requested outside
of the points specified. When zero range clamping is On,
GetValue() returns the value at the value at the lowest
point for a request below all points specified and returns
the value at the highest point for a request above all
points specified. On is the default.
* int = obj.GetClamping () - When zero range clamping is
Off, GetValue() returns 0.0 when a value is requested
outside of the points specified. When zero range clamping
is On, GetValue() returns the value at the value at the
lowest point for a request below all points specified and
returns the value at the highest point for a request above
all points specified. On is the default.
* obj.ClampingOn () - When zero range clamping is Off,
GetValue() returns 0.0 when a value is requested outside
of the points specified. When zero range clamping is On,
GetValue() returns the value at the value at the lowest
point for a request below all points specified and returns
the value at the highest point for a request above all
points specified. On is the default.
* obj.ClampingOff () - When zero range clamping is Off,
GetValue() returns 0.0 when a value is requested outside
of the points specified. When zero range clamping is On,
GetValue() returns the value at the value at the lowest
point for a request below all points specified and returns
the value at the highest point for a request above all
points specified. On is the default.
* string = obj.GetType () - Return the type of function:
Function Types: 0 : Constant (No change in slope between
end points) 1 : NonDecreasing (Always increasing or zero
slope) 2 : NonIncreasing (Always decreasing or zero slope)
3 : Varied (Contains both decreasing and increasing
slopes)
* double = obj.GetFirstNonZeroValue () - Returns the first
point location which precedes a non-zero segment of the
function. Note that the value at this point may be zero.
* obj.Initialize () - Clears out the current function. A
newly created vtkPiecewiseFunction is alreay initialized,
so there is no need to call this method which in turn
simply calls RemoveAllPoints()
* obj.SetAllowDuplicateScalars (int ) - Toggle whether to
allow duplicate scalar values in the piecewise function
(off by default).
* int = obj.GetAllowDuplicateScalars () - Toggle whether to
allow duplicate scalar values in the piecewise function
(off by default).
* obj.AllowDuplicateScalarsOn () - Toggle whether to allow
duplicate scalar values in the piecewise function (off by
default).
* obj.AllowDuplicateScalarsOff () - Toggle whether to allow
duplicate scalar values in the piecewise function (off by
default).
* FreeMat_Documentation
* Visualization_Toolkit_Filtering_Classes
* Generated on Thu Jul 25 2013 17:18:31 for FreeMat by
doxygen_ 1.8.1.1
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