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Synopsis

projectTangent [-caching boolean] [-constructionHistory boolean] [-curvature boolean] [-curvatureScale linear] [-ignoreEdges boolean] [-name string] [-nodeState int] [-object boolean] [-replaceOriginal boolean] [-reverseTangent boolean] [-rotate angle] [-tangentDirection int] [-tangentScale linear] [curve] [[curve] [curve] | [surface]]

projectTangent is undoable, queryable, and editable.

The project tangent command is used to align (for tangents) a curve to two other curves or a surface. A surface isoparm may be selected to define the direction (U or V) to align to. The end of the curve must intersect with these other objects. Curvature continuity may also be applied if required.

Tangent continuity means the end of the curve is modified to be tangent at the point it meets the other objects.

Curvature continuity means the end of the curve is modified to be curvature continuous as well as tangent.

If the normal tangent direction is used, the curvature continuity and rotation do not apply. Also, curvature continuity is only available if align to a surface (not with 2 curves).

Return value

string[]Object name and node name

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

Flags

caching, constructionHistory, curvature, curvatureScale, ignoreEdges, name, nodeState, object, replaceOriginal, reverseTangent, rotate, tangentDirection, tangentScale
Long name (short name) Argument types Properties
-caching(-cch) boolean createqueryedit
Toggle caching for all attributes so that no recomputation is needed
-curvature(-c) boolean createqueryedit
Curvature continuity is on if true and off otherwise.
Default: false
-curvatureScale(-cs) linear createqueryedit
Curvature scale applied to curvature of curve to align. Available if curvature option is true.
Default: 0.0
-ignoreEdges(-ie) boolean createqueryedit
If false, use the tangents of the trim edge curves if the surface is trimmed. If true, use the tangents of the underlying surface in the U/V directions.
Default: false
-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
-reverseTangent(-rt) boolean createqueryedit
Reverse the tangent direction if true and leave it the way it is if false.
Default: false
-rotate(-ro) angle createqueryedit
Amount by which the tangent of the curve to align will be rotated. Available only if the normal direction (3) is not used for tangentDirection.
Default: 0.0
-tangentDirection(-td) int createqueryedit
Tangent align direction type legal values: 1=u direction (of surface or use first curve), 2=v direction (of surface or use second curve), 3=normal direction (at point of intersection).
Default: 1
-tangentScale(-ts) linear createqueryedit
Tangent scale applied to tangent of curve to align.
Default: 1.0
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

// Do project tangent with curvature continuity between a curve and a
// nurbs plane surface
projectTangent -c on curve1 nurbsPlane1;

// Do project tangent between the 3 curves and tangent align the curve
// with the reverse tangent of the second of the other 2 curves
// (i.e. with curve3)
projectTangent -td 2 -rt yes curve1 curve2 curve3;