Dynamic Node Names in MEL Expressions

Question

You know how if you change a nodeName in an expression it will also change the name inside of it as well? Well, how do we go about doing this for stuff like a pointPosition, where the nodeName is inside of a string?

For example:

vector $v = `pointPosition -world "outputCloth1.vtx[11]"`;

If you change outputCloth1’s name to myCloth then the expression stops working, because the string still says outputCloth1!

Answer 1

I think you might be able to achieve what you're looking for via the message attribute. Messages are used to link nodes together in Maya, which (amongst other things) can form the basis of scripts that automatically update names as nodes are renamed.

Sorry I don't have a more concrete example atm, but look into message- that should get you going in the right direction.

Answer 2

Unfortunately, the short answer is that you can't (easily).. expressions within a node can be sort of housekept by Maya because it lives within a portion of Maya's actively monitored framework. The same can't be said for your script because to Maya it's just a bunch of text that it reads and processes whenever you tell it to... Two options sort of present themselves:

1. (If possible) you can rewrite your expressions to refer to objects dynamically For example, if you knew that outputCloth1 was always going to be a child of masterObjectGroup15, you could instead select the first child, instead of referencing by name.

2. Move into PyMEL. This sort of is like #1, in that you're going to be referencing the object and if you change the name, the reference to the object will still be valid. It's probably (okay, it is) beyond the scope of an answer to go into, but I'd strongly suggest you look at the PyMEL getting started docs since they give a pretty good example first up

You could also look into building DG nodes via the Maya API - it's a lot more setup work when compared to scripting, however what you're doing is building something that fits into the standard Maya framework (it's a custom node, basically) - which means you're able to take advantage of all the internal housekeeping that Maya does for you. Yay!