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Synopsis

pointCurveConstraint [-caching boolean] [-constructionHistory boolean] [-name string] [-nodeState int] [-object boolean] [-pointConstraintUVW float float float] [-pointWeight float] [-position float float float] [-replaceOriginal boolean] [-weight float] selectionItem

pointCurveConstraint is undoable, queryable, and editable.

The command enables direct manipulation of a NURBS curve. It does so by apply a position constraint at the specified parameter location on the NURBS curve.

If construction history for the cmd is enabled, a locator is created to enable subsequent interactive manipulation of the curve. The locator position may be key framed or transformed and the "curve1" will try to match the position of the locator.

The argument is a curve location

Return value

string[]Object Name(s), node name.

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

Flags

caching, constructionHistory, name, nodeState, object, pointConstraintUVW, pointWeight, position, replaceOriginal, weight
Long name (short name) Argument types Properties
-caching(-cch) boolean createqueryedit
Toggle caching for all attributes so that no recomputation is needed
-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
-pointConstraintUVW(-puv) float float float createqueryedit
Point constraint parameter space location on input NURBS Object
-pointWeight(-pw) float createqueryedit
Point constraint weight. Determines how strong an influence the constraint has on the input NURBS object.
Default: 1.0
-position(-p) float float float create
The new desired position in space for the nurbs object at the specified parameter space component. If not specified, the position is taken to be the one evaluated at the parameter space component on the nurbs object.
-weight(-w) float create
weight of the lsq constraint. The larger the weight, the least squares constraint is strictly met.
Common flags
-constructionHistory(-ch) boolean create
Turn the construction history on or off.
-name(-n) string create
Sets the name of the newly-created node. If it contains namespace path, the new node will be created under the specified namespace; if the namespace does not exist, it will be created.
-object(-o) boolean create
Create the result, or just the dependency node.
-replaceOriginal(-rpo) boolean create
Create "in place" (i.e., replace).
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

// Apply a constraint to manipulate the  position corresponding to
// the 1st edit point on curve1.
pointCurveConstraint -ch true curve1.ep[1] ;

// Apply a constraint to manipulate the end point on curve1.
pointCurveConstraint -ch true -w 1.0 curve1.un[1.0] ;

// Apply a constraint around the midpoint in the parameter domain on curve1.
pointCurveConstraint -ch true -w -1.0 curve1.un[0.5] ;