Create object via MEL

[joiec...@gmail.com]

Hi there,

I need to create several objects and connect their translation to an attribute of corresponding node.

So in its simplest form, it would be like this:

createNode -n Loc1 "locator";

createNode -n Pos1 "locator";

connectAttr Loc1.translateX Pos1.scaleX;

You get the idea. I create two objects and connect the attribute from one to the attribute on the other one.

But I want to do this in a loop. So I need each object's name to be unique (obvious).

So I would need something like the above example, but with names like "Loc_[n]" instead (so the [n] is a number).

How could I do that in a loop?

Thanks in advance for your help.

[stephenkmann]

Welcome to the world of scripting !

okay. so Loops in mel  and python are fairly simple. but you do want to know a little bit about variables first. and how certain commands return what kinds of variables. 

maya has a unique command to create locators..   spaceLocator

this command returns a string array    ( an array is just like a box of stuff. while a string / int / float  are individual items.. so a string array is a box of string variables)

you'll want to capture that string array so you can use it in the loop. 

In Mel. .while it can be implicit, it's good to be explicit with variable declarations ( this is not necc in python) .. to indicate an array you use brackets []

(... also in Mel vairables must start with a dollar sign     ie  $myVariable   or  $myVariable[] )

string $loc[] = `spaceLocator -name "loc"`;

string $pos[] = `spaceLocator -name "pos"`;

and then once you've created those string array variables  you'll want access to the item you want.. you can use a #  as to choose which item.. ie : $loc[0] is the first item, and $loc[1] is the second item 

the connection part is pretty easy, basicaly what you have, but replace strings with variables

connectAttr ( $loc[0] + "." + "scaleX") ( $pos[0] + "." + "scaleX") ;

and then lastly make a loop.   so a for loop will run once for each item given..    this is the more common .. however, if you just want to run a number of times. you need to use a while loop.. 

while loops can be dangerous, as you can easily get into an infinite loop, so be sure to increment your item  ( shorthand for this is ++ ) 

and then lastly, I strongly recommend always putting your MEL code in scope. that way you don't create global variables.. Unlike Python, MEL cannot change variable types, so once you make one. it's that type forever. 

if it is run scoped.. then it only exists within that scope.  ( * what's between the curly brackets) 

{
int $i = 0 ;
while ($i <= 10)
    {
    string $loc[] = `spaceLocator -name "loc"`;
    string $pos[] = `spaceLocator -name "pos"`;  
    connectAttr ( $loc[0] + "." + "scaleX")  ($pos[0] + "." + "scaleX") ;
   
    $i++;
     
    }
}

okay, so Should kickstart what you are looking to do.. Funny part is I used to write MEL in  my sleep, but since I converted to PYTHON a few years back,  my mel is getting quite rusty. 

good luck. hope that helps, safe travels, save often !

-=s

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[bobrobertuma]

Great job showing mel scripting process in simple terms.

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[SEQUENZ | Gerstenmaier]

Yes, your explanation lures all weak souls into the world of scripting! 

Thanks for your effort,

Lars

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SEQUENZ GmbH 
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[joie]

Man, that is probably the best explanation on loops and variables I ever saw!

Very thank you! :)

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[matt estela]

Indeed, awesome answer!

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[desig...@gmail.com]

+1

Nicely done!

R

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[elvis]

perfect!

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