FCurveKey.LeftTanX

Description

Sets or returns the left tangent X (in frames) of the fcurve key relative to the FCurveKey.Time value as a Double.

The left tan x value may be a negative value between a distance which is one third the distance between 2 consecutive key and 0; this guarantees that the curve is valid.

The left tangent of the first key and the right tangent of the last key cannot be changed. If you try to set the tangent for one of these the property does nothing and returns S_FALSE in C++.

Tangent values only apply to standard function curves (where FCurve.Type = siStandardFCurve), the tangent value 0 is returned for all other function curve types defined by siFCurveType.

C# Syntax

// get accessor

Object rtn = FCurveKey.LeftTanX;

// set accessor

FCurveKey.LeftTanX = Object;

Examples

1. JScript Example

/*

	This example illustrates how to create an fcurve and set the tangents on a specific key

*/

// Create new scene

NewScene( "", false );

// Create a null

var nullobj = Application.ActiveSceneRoot.AddNull();

// Get the posx parameter from the null

var posx = nullobj.posx;

// Create an fcurve on posx

var fc = posx.AddFCurve2();

// Define some keys (3 key-value pairs)

var keyvalues = new Array( 0,0, 50,25, 100,50 );

fc.SetKeys( keyvalues );

// Get the 1st, 2nd & 3rd FCurveKey objects

var key0 = fc.Keys(0);

var key1 = fc.Keys(1);

var key2 = fc.Keys(2);

// Make the key non-G1 continuous so it can have different left and right values

key1.Constraint( siG1ContinuousConstraint ) = false;

key1.LeftTanX = 0;

key1.LeftTanY = Math.abs( key1.Value - key0.Value );

key1.RightTanX = key2.Time - key1.Time;

key1.RightTanY = 0;

PrintKeys( fc );

// Convenience function to print the FCurveKeys

function PrintKeys( in_fcrv )

{

	for ( var i=0; i<in_fcrv.Keys.Count; i++ ) {

		var fckey = in_fcrv.Keys(i);

		var str = "key : " + fckey.Index;

		str += "\n\ttime : " + fckey.Time;

		str += "\n\tvalue : " + fckey.Value;

		str += "\n\ttangents : " + fckey.LeftTanX + "," + fckey.LeftTanY + "," + fckey.RightTanX + "," + fckey.RightTanY;

		str += "\n\tconstraints : " + GetConstraintType( fckey );

		Application.LogMessage( str );

	}

}

// Convenience function to get the user-friendly string describing the contraint type

function GetConstraintType( in_fcrvkey )

{

	var ConstraintTypes = new Array (

		new Array (siParameterConstraint,			"LockParameter"),

		new Array (siLeftRightValuesConstraint,			"LeftRightParameter"),

		new Array (siG1ContinuousConstraint,			"G1Continuous"),

		new Array (siLeftRightTangentDirectionConstraint,	"LeftRightTangentDirection"),

		new Array (siLeftRightTangentLengthConstraint,		"LeftRightTangentLength"),

		new Array (siLockConstraint,				"LockAll"),

		new Array (siHorizontalTangentConstraint,		"HorizontalTangent"),

		new Array (siExtremumHorizontalTangentConstraint,	"ExtremumHorizontalTangent"),

		new Array (siAdjustedTangentConstraint,			"AdjustedTangent"),

		new Array (siZeroLengthTangentConstraint,		"ZeroLengthTangent"),

		new Array (siSameLengthTangentConstraint,		"SameLengthTangent"), 

		new Array (siNeighborTangentConstraint,			"NeighborTangent"),

		new Array (siMirrorTangentConstraint,			"MirrorTangent"),

		new Array (siAutoPlateauTangentConstraint,		"AutoPlateauTangent") 

	)

	var str = "";

	for ( var i=0; i<ConstraintTypes.length; i++ ) {

		if ( in_fcrvkey.Constraint( ConstraintTypes[i][0] ) ) {

			str += ConstraintTypes[i][1] + " ";

		}		 

	}

	return str;

}

// Expected results:

//INFO : key : 0

//	time : 0

//	value : 0

//	tangents : -16.666666666666668,0,16.666666666666668,0

//	constraints : G1Continuous  

//INFO : key : 1

//	time : 50

//	value : 25

//	tangents : 0,25,50,0

//	constraints : 

//INFO : key : 2

//	time : 100

//	value : 50

//	tangents : -16.666666666666664,0,16.666666666666664,0

//	constraints : G1Continuous

2. VBScript Example

'

' This example illustrates how to create an fcurve and set the tangents on a specific key

' 

' Create new scene

NewScene , false 

' Create a null

set nullobj = Application.ActiveSceneRoot.AddNull()

' Get the posx parameter from the null

set posx = nullobj.posx

' Create an fcurve on posx

set fc = posx.AddFCurve2()

' Define some keys (3 key-value pairs)

keyvalues = array( 0,0, 50,25, 100,50 )

fc.SetKeys keyvalues 

' Get the 1st, 2nd & 3rd FCurveKey objects

set key0 = fc.Keys(0)

set key1 = fc.Keys(1)

set key2 = fc.Keys(2)

' Make the key non-G1 continuous so it can have different left and right values

key1.Constraint( siG1ContinuousConstraint ) = false

key1.LeftTanX = 0

key1.LeftTanY = Abs( key1.Value - key0.Value )

key1.RightTanX = key2.Time - key1.Time

key1.RightTanY = 0

PrintKeys fc 

' Convenience routine to print the FCurveKeys

sub PrintKeys( in_fcrv )

	for each fckey in in_fcrv.Keys

		str = "key : " & fckey.Index

		str = str & vbCrLf & vbTab & "time : " & fckey.Time

		str = str & vbCrLf & vbTab & "value : " & fckey.Value

		str = str & vbCrLf & vbTab & "tangents : " & fckey.LeftTanX & "," & fckey.LeftTanY & "," & fckey.RightTanX & "," & fckey.RightTanY

		str = str & vbCrLf & vbTab & "constraints : " & GetConstraintType( fckey )

		Application.LogMessage str 

	next

end sub

' Convenience function to get the user-friendly string describing the contraint type

function GetConstraintType( in_fcrvkey )

	set ConstraintTypes = CreateObject( "Scripting.Dictionary" )

	ConstraintTypes.Add siParameterConstraint, 			"LockParameter"

	ConstraintTypes.Add siLeftRightValuesConstraint,		"LeftRightParameter"

	ConstraintTypes.Add siG1ContinuousConstraint,			"G1Continuous"

	ConstraintTypes.Add siLeftRightTangentDirectionConstraint,	"LeftRightTangentDirection"

	ConstraintTypes.Add siLeftRightTangentLengthConstraint,		"LeftRightTangentLength"

	ConstraintTypes.Add siLockConstraint,				"LockAll"

	ConstraintTypes.Add siHorizontalTangentConstraint,		"HorizontalTangent"

	ConstraintTypes.Add siExtremumHorizontalTangentConstraint,	"ExtremumHorizontalTangent"

	ConstraintTypes.Add siAdjustedTangentConstraint,		"AdjustedTangent"

	ConstraintTypes.Add siZeroLengthTangentConstraint,		"ZeroLengthTangent"

	ConstraintTypes.Add siSameLengthTangentConstraint,		"SameLengthTangent"

	ConstraintTypes.Add siNeighborTangentConstraint,		"NeighborTangent"

	ConstraintTypes.Add siMirrorTangentConstraint,			"MirrorTangent"

	ConstraintTypes.Add siAutoPlateauTangentConstraint,		"AutoPlateauTangent"

	str = ""

	for each k in ConstraintTypes.Keys

		if in_fcrvkey.Constraint( k ) then

			str = str & ConstraintTypes(k) & " "

		end if

	next

	GetConstraintType = str

end function

' Expected results:

'INFO : key : 0

'	time : 0

'	value : 0

'	tangents : -16.6666666666667,0,16.6666666666667,0

'	constraints : G1Continuous  

'INFO : key : 1

'	time : 50

'	value : 25

'	tangents : 0,25,50,0

'	constraints : 

'INFO : key : 2

'	time : 100

'	value : 50

'	tangents : -16.6666666666667,0,16.6666666666667,0

'	constraints : G1Continuous

3. Python Example

#

# This example illustrates how to create an fcurve and set the tangents on a specific key

# 

from win32com.client import constants as c

# Convenience function to get the user-friendly string describing the contraint type

def GetConstraintType( in_fcrvkey ) :

	ConstraintTypes = {

		c.siParameterConstraint:"LockParameter", 

		c.siLeftRightValuesConstraint:"LeftRightParameter", 

		c.siG1ContinuousConstraint:"G1Continuous", 

		c.siLeftRightTangentDirectionConstraint:"LeftRightTangentDirection", 

		c.siLeftRightTangentLengthConstraint:"LeftRightTangentLength", 

		c.siLockConstraint:"LockAll", 

		c.siHorizontalTangentConstraint:"HorizontalTangent", 

		c.siExtremumHorizontalTangentConstraint:"ExtremumHorizontalTangent", 

		c.siAdjustedTangentConstraint:"AdjustedTangent", 

		c.siZeroLengthTangentConstraint:"ZeroLengthTangent", 

		c.siSameLengthTangentConstraint:"SameLengthTangent",

		c.siNeighborTangentConstraint:"NeighborTangent",

		c.siMirrorTangentConstraint:"MirrorTangent",

		c.siAutoPlateauTangentConstraint:"AutoPlateauTangent"

	}

	str = ""

	for k in ConstraintTypes.keys() :

		if ( in_fcrvkey.Constraint(k) ) :

			str += ConstraintTypes[k] + " "

	return str

# Convenience function to print the FCurveKeys

def PrintKeys( in_fcrv ) :

	for fckey in in_fcrv.Keys :

		str = "key : %d" % (fckey.Index)

		str = str + "\n\ttime : %d" % (fckey.Time)

		str = str + "\n\tvalue : %d" % (fckey.Value)

		str = str + "\n\ttangents : %d,%d,%d,%d" % (fckey.LeftTanX,fckey.LeftTanY,fckey.RightTanX,fckey.RightTanY)

		str = str + "\n\tconstraints : " + GetConstraintType( fckey )

		Application.LogMessage( str )

	return None

# Create new scene

Application.NewScene( "", 0 )

# Create a null

nullobj = Application.ActiveSceneRoot.AddNull()

# Get the posx parameter from the null

posx = nullobj.posx

# Create an fcurve on posx

fc = posx.AddFCurve2()

# Define some keys (3 key-value pairs)

keyvalues = [ 0,0, 50,25, 100,50 ]

fc.SetKeys( keyvalues )

# Get the 1st, 2nd & 3rd FCurveKey objects

key0 = fc.Keys(0)

key1 = fc.Keys(1)

key2 = fc.Keys(2)

# Make the key non-G1 continuous so it can have different left and right values

# (Python can't use the Constraint property as-is, so use SetConstraint as an alias)

key1.SetConstraint( c.siG1ContinuousConstraint, 0 )

key1.LeftTanX = 0

key1.LeftTanY = abs( key1.Value - key0.Value )

key1.RightTanX = key2.Time - key1.Time

key1.RightTanY = 0

PrintKeys( fc )

# Expected results:

# INFO : key : 0

# 	time : 0

# 	value : 0

# 	tangents : -16,0,16,0

# 	constraints : G1Continuous 

# INFO : key : 1

# 	time : 50

# 	value : 25

# 	tangents : 0,25,50,0

# 	constraints : 

# INFO : key : 2

# 	time : 100

# 	value : 50

# 	tangents : -16,0,16,0

# 	constraints : G1Continuous

See Also

FCurve.SetKeyTangents FCurveKey.LeftTanY FCurveKey.RightTanY FCurveKey.RightTanX

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