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hie i have a slight confusion as to why what writing is not working. in my MEL script editor I'm writing

string $Adistance = ("distanceDimensionShape1"+".distance");
expression -s (" $Bdistance = $Adistance; joint2.scaleX = $distance");

but I get this error 

// Warning: line 1: Converting string "distanceDimensionShape1.distance" to a float value of 0. //
  • I want joint2.scaleX to copy distanceDimensionShape1.distance float
Raspberry
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  • SORRY wrote it incorrectly this is the real problem float $distance = ("distanceDimensionShape1"+".distance"); expression -s (" $distance = $distance;"); – Raspberry Feb 16 '15 at 15:23
  • What exactly is it you're trying to achieve with this expression and MEL script? It's hard to discern the solution with an expression that only sets a variable. And when you need to clarify the question, it often makes more sense to [edit] the question itself rather than cram the change in a comment. – mhlester Feb 16 '15 at 16:18
  • I want joint2.scaleX to copy distanceDimensionShape1.distance float – Raspberry Feb 16 '15 at 16:48

2 Answers2

1

Ok, so first I'm not a Mel programmer, I usually do my script in Python so there might be syntax errors in my code.

Your problem:

Correct me if I'm wrong, but I think you are trying to get the distance attribute of distanceDimensionShape1 into a variable and set it to scaleX attribute from joint2.

Your code:

string $Adistance = ("distanceDimensionShape1"+".distance");
expression -s (" $Bdistance = $Adistance; joint2.scaleX = $distance");

What you are doing in your 1st line: You are declaring a string variable containing "distanceDimensionShape1.distance", not getting the distance attribute of distanceDimensionShape1

What you should be doing in your 1st line: Use the getAttr command provided in maya docs the retrieve the attribute of your shape.

What you are doing in your second line: You are trying to set joint2.scaleX which is a float value with a string value. I guess... because I don't know what's $distance as it appears only here in your code.

What you should be doing in your second line: Use setAttr to properly set your attribute.

My solution:

I hope this will help as we have only few informations on your current problem:

float $Adistance = `getAttr distanceDimensionShape1.distance`;
setAttr joint2.scaleX  $Adistance;

1st line retrieves properly the selected attributes and storages it to a float. 2nd line set your attribute with the retrieved value.

Note:

  • You can watch which methods are called when doing manipulation in maya by opening your script editor and checking History > Echo All Commands. This way you will be able to reproduce Maya's behaviour.
  • Always have an internet browser pointing to Maya's Mel/Python doc when scripting: link

  • Try to develop more when posting a question on SO:

    1. What are your trying to achieve and how you plan to do it

    2. A commented block of code (approx 10-15 lines is fine and give a good overview of your mel script)

    3. What's your error message

Hope this will help.

DrHaze
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1

If you want to create an expression once then change what connects to it, create it the following way:

expression -s ("joint2.scaleX = .I[0]")

Then you can connect a specific attribute to that plug like this:

connectAttr distanceDimensionShape1.distance expression1.input[0]

This is assuming there's a legitimate reason you couldn't just write the expression once directly:

expression -s ("joint2.scaleX = distanceDimensionShape1.distance")
mhlester
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