Re: [Maya-Python] How can I use a Dependency Node plug-in inside Maya?

[Joe Weidenbach]

Hi Carlos,

Dependency Nodes are basically (once created) like other dependency nodes in Maya.  So, you can (once the plugin is loaded, either through script or through the plugins manager) call createNode('<your plugin's node name>"), which will create your node, and then you just connect and/or set attrs on that node.  It's identical to, say, a multiplyDivide node or a plusMinusAverage.

Hope that helps,

Joe

On Tue, Jan 13, 2015 at 1:32 AM, Carlos Montes <carlos...@gmail.com> wrote:

Hello, everyone. I have just finished Robert Galanakis' "Practical Maya Programming with Python" book, where in its Chapter 8 a dependency graph plug-in is developed. My problem is, I don't know how it can be used or invoked inside Maya; using plug-ins for this software is new for me. I will provide some code from the book to try to expose where my doubtfulness resides, but the question remains the

In Chapter 7, he teaches us a Command plug-in can be called with pymel.core's loadPlugin in the Script Editor, and then a plugin_name variable that was defined inside the Python plugin file can be used as a method that invokes the plugin.

This is what it would look like in the Script Editor's Python tab, for a Command plug-in to be used :

import pymel.core as pmc                 
pmc.loadPlugin('playsoundplugin.py')  
pmc.playSound()                               

Inside 'playsoundplugin.py', that variable called plugin_name is defined as the method you invoke to play a Sound in Maya, by using a creator function and initializing the plugin with registerCommand.

plugin_name = 'playSound'

def create_plugin():
    return OpenMayaMPx.asMPxPtr(SoundPlayer())

def initializePlugin(mobject):
   plugin = OpenMayaMPx.MFnPlugin(mobject)
   plugin.registerCommand(plugin_name, create_plugin)

It's very straightforward, and it all makes sense with has been taught in the book; he even offers a very interesting way to add flags to the command call.
For Chapter 8, though, he doesn't show how we can use the quite complex Dependency Node plugin where he creates a node and its attributes with specifications and concrete subclasses. The plugin takes three input values, and a compute function takes care of determining two output attributes.

Similar to the Command plugin creation, the node plugin also uses similar creator and initialization functions; but this time, a new type with the 'circler' name is created:

def register_circler(fnplugin):
    inputnames = ['input', 'scale', 'frames']
    reg, dereg = create_node(NT_DEPENDSNODE, 'circler', 0x60005, [ value1, value2, value3 ])
    reg(fnplugin)

def initializePlugin(mobject):
    register_circler(OpenMayaMPx.MFnPlugin(mobject))

And here is where my question is; Command plug-ins can be called with the plugin_name variable, but how can I use a Dependency Node plugin then? How can I create this dependency node with input and output attributes inside Maya? Do all Dependency Node plugins share the same procedure to be used?

I hope the question is not too vague or non understandable. Thank you for reading.

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[Carlos Montes]

I see, so it will become visible in, say, the Hypergraph or the Connection Editor, and I can then manipulate its inputs like I do with other nodes.

That makes a lot of sense! Thank you. I also found this helpful read from Autodesk that describes what we can do with the Dependency Graph and how it works.

Thanks again, Joe!

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[Joe Weidenbach]

No Problem, Carlos!

Glad I could help!  Also, now that I think about it, it will also show up just fine in the node editor as well :)  Good find on the dependency graph!

Joe

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