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.
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