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curve(
string
, [append=boolean], [bezier=boolean], [degree=float], [editPoint=[linear, linear, linear]], [knot=float], [name=string], [objectSpace=boolean], [periodic=boolean], [point=[linear, linear, linear]], [pointWeight=[linear, linear, linear, float]], [replace=boolean], [worldSpace=boolean])
Note: Strings representing object names and arguments must be separated by commas. This is not depicted in the synopsis.
curve is undoable, NOT queryable, and NOT editable.
The curve command creates a new curve from a list of control vertices
(CVs). A string is returned containing the pathname to the newly
created curve. You can create a curve from points either in world
space or object (local) space, either with weights or without.
You can replace an existing curve by using the "r/replace"
flag. You can append a point to an existing curve by using the
"a/append" flag.
To create a curveonsurface, use the curveOnSurface command.
To change the degree of a curve, use the rebuildCurve command.
To change the of parameter range curve, use the rebuildCurve command.
string  The path to the new curve or the replaced curve 
curveOnSurface
append, bezier, degree, editPoint, knot, name, objectSpace, periodic, point, pointWeight, replace, worldSpace
Long name (short name) 
Argument types 
Properties 

append(a)

boolean



Appends point(s) to the end of an existing curve.
If you use this flag, you must specify the name of the
curve to append to, at the end of the command. (See examples below.)


bezier(bez)

boolean



The created curve will be a bezier curve.


degree(d)

float



The degree of the new curve. Default is 3. Note that you need
(degree+1) curve points to create a visible curve span. eg. you
must place 4 points for a degree 3 curve.


editPoint(ep)

[linear, linear, linear]



The x, y, z position of an edit point. "linear" means that this flag
can take values with units. This flag can not be used with
the point or the pointWeight flags.


knot(k)

float



A knot value in a knot vector. One flag per knot value.
There must be (numberOfPoints + degree  1) knots and the knot
vector must be nondecreasing.


name(n)

string



objectSpace(os)

boolean



Points are in object, or "local" space. This is the default.
You cannot specify both "os" and "ws" in the same command.


periodic(per)

boolean



If on, creates a curve that is periodic. Default is off.


point(p)

[linear, linear, linear]



The x, y, z position of a point. "linear" means that this flag
can take values with units.


pointWeight(pw)

[linear, linear, linear, float]



The x,y,z and w values of a point, where the w is a weight value.
A rational curve will be created if this flag is used.
"linear" means that this flag can take values with units.


replace(r)

boolean



Replaces an entire existing curve.
If you use this flag, you must specify the name of the curve to
replace, at the end of the command. (See examples below.)


worldSpace(ws)

boolean



Points are in world space. The default is "os".
You cannot specify both "os" and "ws" in the same command.


Flag can appear in Create mode of command

Flag can appear in Edit mode of command

Flag can appear in Query mode of command

Flag can have multiple arguments, passed either as a tuple or a list.

import maya.cmds as cmds
# These commands create curves with four control vertices.
# The first one is created without weights. The third command
# shows how you can use units to specify position.
cmds.curve( p=[(0, 0, 0), (3, 5, 6), (5, 6, 7), (9, 9, 9)] )
cmds.curve( pw=[(0, 0, 0, 1), (3, 5, 6, 1), (5, 6, 7, 1), (9, 9, 9, 1)] )
cmds.curve( p=[('0cm', '0cm', '0cm'), ('3in', '5in', '6in'), ('5ft', '6ft', '7ft'), (9, 9, 9)] )
# This command replaces an existing curve, curve1, with the given points.
# Do not use this flag on a curve that is a result of a construction
# history operation.
cmds.curve( 'curve1', r=True, p=[(0, 0, 0), (3, 5, 6), (10, 12, 14), (9, 9, 9)] )
# This command adds two CVs to an existing curve, curve1.
# The "ws" flag can be used if the specified CVs are in world space.
# Do not use this flag on a curve that is a result of a construction
# history operation.
cmds.curve( 'curve1', a=True, p=[(13, 13, 13), (13, 15, 16)] )
# This command creates a curve with five control vertices,
# with a knot vector. Notice that there must be
# (number of CVs + degree  1) knots and that the knot
# vector must be nondecreasing.
cmds.curve( p=[(0, 0, 0), (3, 5, 6), (5, 6, 7), (9, 9, 9), (12, 10, 2)], k=[0,0,0,1,2,2,2] )
# This command creates a closed (or "periodic") curve with
# four distinct CVs. You must specify a knot vector when the
# "per" flag is used. Notice that the first "degree" points
# are the same as the last "degree" points (ie. the first three
# points are the same as the last three points). Notice also
# that the knot spacing between the first "degree" knots must
# be the same as the spacing between the last "degree" knots
# (ie. the space between the 1st and 2nd knots is the same as
# the space between the 7th and 8th knots, and the space between
# the 2nd and 3rd knots is the same as the space between the
# 8th and 9th knots). There must be space between the first
# "degree" knots, unlike the previous example, where the first
# "degree" knots are the same.
cmds.curve( per=True, p=[(0, 0, 0), (3, 5, 6), (5, 6, 7), (9, 9, 9), (0, 0, 0), (3, 5, 6), (5, 6, 7)], k=[2,1,0,1,2,3,4,5,6] )
# How to query curve properties:
# This returns the degree of the curve. Note that the
# number of CVs = degree + spans.
cmds.getAttr( 'curve1.degree' )
# This returns the number of spans in the curve. Note that the
# number of CVs = degree + spans.
cmds.getAttr( 'curve1.spans' )
# This returns the curve form.
cmds.getAttr( 'curve1.form' )
# This returns the minimum parameter value on the curve.
cmds.getAttr( 'curve1.minValue' )
# This returns the maximum parameter value on the curve.
cmds.getAttr( 'curve1.maxValue' )
# This returns the local x,y,z of the 1st CV. Use a curve info node if
# the curve is a result of a construction history operation.
cmds.getAttr( 'curve1.cv[0]' )
# This returns the local x,y,z of the 1st three CVs. Use a curve info
# node if the curve is a result of a construction history operation.
cmds.getAttr( 'curve1.cv[*]' )
# This returns the local x,y,z of all CVs. Use a curve info node if
# the curve is a result of a construction history operation.
cmds.getAttr( 'curve1.cv[0:2]' )
# This returns the arc length of the curve. Use "ch" flag with
# the arclen command to get a curve info node that constantly updates
# to the current arc length.
cmds.arclen( 'curve1' )
# This sequence creates a curve info node, connects the info node to the
# curve and queries the knot vector of the curve using the curve info node.
# You can use the curve info node to query other attributes such as
# world space CV values and arc length.
cmds.createNode( 'curveInfo' )
cmds.connectAttr( 'curveShape1.worldSpace', 'curveInfo1.inputCurve' )
cmds.getAttr( 'curveInfo1.knots[*]' )