PiecewiseFunction

Source (.js)Source (.d.ts)

Introduction

vtkPiecewiseFunction 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).

Usage

const ofun = vtkPiecewiseFunction.newInstance();
ofun.addPoint(200.0, 0.0);
ofun.addPoint(1200.0, 0.2);
ofun.addPoint(4000.0, 0.4);

See Also

vtkColorTransferFunction

Methods

addPoint

Add points to the function.

Argument	Type	Required	Description
x	Number	Yes	The x coordinate.
y	Number	Yes	The y coordinate.

addPointLong

Add points to the function.

Argument	Type	Required	Description
x	Number	Yes	The x coordinate.
y	Number	Yes	The y coordinate.
midpoint	Number	Yes
sharpness	Number	Yes

addSegment

Add a line segment to the function.

Argument	Type	Required	Description
x1	Number	Yes	The first point x coordinate.
y1	Number	Yes	The first point y coordinate.
x2	Number	Yes	The second point x coordinate.
y2	Number	Yes	The second point y coordinate.

adjustRange

Remove all points out of the new range, and make sure there is a point at each end of that range.

Argument	Type	Required	Description
range	Range	Yes

estimateMinNumberOfSamples

Estimates the minimum size of a table such that it would correctly sample this function.

extend

Method used to decorate a given object (publicAPI+model) with vtkPiecewiseFunction characteristics.

Argument	Type	Required	Description
publicAPI		Yes	object on which methods will be bounds (public)
model		Yes	object on which data structure will be bounds (protected)
initialValues	IPiecewiseFunctionInitialValues	No	(default: {})

findMinimumXDistance

Traverses the nodes to find the minimum distance.

getAllowDuplicateScalars

Toggle whether to allow duplicate scalar values in the piecewise function (off by default).

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.

getDataPointer

Returns a pointer to the data stored in the table.

getFirstNonZeroValue

Returns the first point location which precedes a non-zero segment of the function.

getNodeValue

For the node specified by index, set/get the location (X), value (Y), midpoint, and sharpness values at the node.

Argument	Type	Required	Description
index	Number	Yes
val		Yes

getRange

Returns the min and max node locations of the function.

getRangeByReference

Returns the min and max node locations of the function.

getSize

Get the number of points used to specify the function.

getTable

Fills in an array of function values evaluated at regular intervals.

Argument	Type	Required	Description
xStart	Number	Yes
xEnd	Number	Yes
size	Number	Yes
table		Yes
stride	Number	No

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)

getValue

Returns the value of the function at the specified location using the specified interpolation.

newInstance

Method used to create a new instance of vtkPiecewiseFunction.

Argument	Type	Required	Description
initialValues	IPiecewiseFunctionInitialValues	No	for pre-setting some of its content

removeAllPoints

Removes all points from the function.

removePoint

Remove the first point found at the given x location Return the index of the remove point if any, -1 otherwise.

Argument	Type	Required	Description
x	Number	Yes

setAllowDuplicateScalars

Argument	Type	Required	Description
allowDuplicateScalars	Boolean	Yes

setClamping

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.

Argument	Type	Required	Description
clamping	Boolean	Yes

setNodeValue

Argument	Type	Required	Description
index	Number	Yes
val		Yes

setNodes

Argument	Type	Required	Description
nodes		Yes

setRange

Argument	Type	Required	Description
min	Number	Yes
max	Number	Yes

setRange

Argument	Type	Required	Description
range	Range	Yes

setRangeFrom

Argument	Type	Required	Description
range	Range	Yes

sortAndUpdateRange

Internal method to sort the vector and update the Range whenever a node is added, edited or removed.

updateRange

Returns true if the range has been updated and Modified() has been called.