Go to: Synopsis. Return value. Flags. MEL examples.

Synopsis

pointOnCurve [-caching boolean] [-constructionHistory boolean] [-curvatureCenter] [-curvatureRadius] [-nodeState int] [-normal] [-normalizedNormal] [-normalizedTangent] [-parameter float] [-position] [-tangent] [-turnOnPercentage boolean] [objects]

pointOnCurve is undoable, queryable, and editable.

This command returns information for a point on a NURBS curve. If no flag is specified, it assumes p/position by default.

Return value

float[3]Vector query result
floatSingle float query result
stringString query result

In query mode, return type is based on queried flag.

Flags

caching, constructionHistory, curvatureCenter, curvatureRadius, nodeState, normal, normalizedNormal, normalizedTangent, parameter, position, tangent, turnOnPercentage
Long name (short name) Argument types Properties
Common flags
-caching(-cch) boolean createqueryedit
Toggle caching for all attributes so that no recomputation is needed
-constructionHistory(-ch) boolean create
Turn the construction history on or off.
-curvatureCenter(-cc) create
Returns the (x,y,z) center of curvature of the specified point on the curve
-curvatureRadius(-cr) create
Returns the radius of curvature of the specified point on the curve
-nodeState(-nds) int createqueryedit

Maya dependency nodes have 6 possible states. The Normal (0), HasNoEffect (1), and Blocking (2) states can be used to alter how the graph is evaluated.

The Waiting-Normal (3), Waiting-HasNoEffect (4), Waiting-Blocking (5) are for internal use only. They temporarily shut off parts of the graph during interaction (e.g., manipulation). The understanding is that once the operation is done, the state will be reset appropriately, e.g. Waiting-Blocking will reset back to Blocking.

The Normal and Blocking cases apply to all nodes, while HasNoEffect is node specific; many nodes do not support this option. Plug-ins store state in the MPxNode::state attribute. Anyone can set it or check this attribute. Additional details about each of these 3 states follow.

State Description
Normal The normal node state. This is the default.
HasNoEffect

The HasNoEffect option (a.k.a. pass-through), is used in cases where there is an operation on an input producing an output of the same data type. Nearly all deformers support this state, as do a few other nodes. As stated earlier, it is not supported by all nodes.

It’s typical to implement support for the HasNoEffect state in the node’s compute method and to perform appropriate operations. Plug-ins can also support HasNoEffect.

The usual implementation of this state is to copy the input directly to the matching output without applying the algorithm in the node. For deformers, applying this state leaves the input geometry undeformed on the output.

Blocking

This is implemented in the depend node base class and applies to all nodes. Blocking is applied during the evaluation phase to connections. An evaluation request to a blocked connection will return as failures, causing the destination plug to retain its current value. Dirty propagation is indirectly affected by this state since blocked connections are never cleaned.

When a node is set to Blocking the behavior is supposed to be the same as if all outgoing connections were broken. As long as nobody requests evaluation of the blocked node directly it won’t evaluate after that. Note that a blocked node will still respond to getAttr requests but a getAttr on a downstream node will not reevaluate the blocked node.

Setting the root transform of a hierarchy to Blocking won’t automatically influence child transforms in the hierarchy. To do this, you’d need to explicitly set all child nodes to the Blocking state.

For example, to set all child transforms to Blocking, you could use the following script.


import maya.cmds as cmds
def blockTree(root):
nodesToBlock = []
for node in {child:1 for child in cmds.listRelatives( root, path=True, allDescendents=True )}.keys():
nodesToBlock += cmds.listConnections(node, source=True, destination=True )
for node in {source:1 for source in nodesToBlock}.keys():
cmds.setAttr( '%s.nodeState' % node, 2 )

Applying this script would continue to draw objects but things would not be animated.


Default: kdnNormal
-normal(-no) create
Returns the (x,y,z) normal of the specified point on the curve
-normalizedNormal(-nn) create
Returns the (x,y,z) normalized normal of the specified point on the curve
-normalizedTangent(-nt) create
Returns the (x,y,z) normalized tangent of the specified point on the curve
-parameter(-pr) float queryedit
The parameter value on curve
Default: 0.0
-position(-p) create
Returns the (x,y,z) position of the specified point on the curve
-tangent(-t) create
Returns the (x,y,z) tangent of the specified point on the curve
-turnOnPercentage(-top) boolean queryedit
Whether the parameter is normalized (0,1) or not
Default: false

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 be used more than once in a command.

MEL examples

pointOnCurve -pr 0.5 -p curve1;
// Returns the (x,y,z) position of curve1 at parameter 0.5.

pointOnCurve -pr 0.5 curve1;
// Returns the (x,y,z) position of curve1 at parameter 0.5, since
// position is the default information.

pointOnCurve -pr 0.5 -nn curve1;
// Returns the (x,y,z) normalized normal of curve1 at parameter 0.5.

pointOnCurve -pr 0.5 -cr curve1;
// Returns the curvature radius of curve1 at parameter 0.5.

string $infoNode = `pointOnCurve -ch on -pr 0.55 curve1`;
getAttr ($infoNode + ".position");    // returns the position
getAttr ($infoNode + ".normal");      // returns the normal
// Returns a string which is the name of a new pointOnCurveInfo
// dependency node.  With this node connected to the curve,
// the output values of the pointOnCurveInfo node are always current
// even if, for example, the parameter is being animated.