Art of Rigging - script questions!

[Buexe]

the setParent command tells Maya that the current layout does not get more controls and/or other layouts, kind of like you described it although there is no such thing as a window layout in Maya. Imagine your GUI has different layouts and they have a hierarchical order with parent/child relationships and branches. In the case you specified the setParent command is kind of useless, because no other controls/layouts are specified after the setParent command.

Regarding the eval thing I guess it should work the way you described it without the eval thing. But maybe the authors had a reason to do it this way, so ... can`t really help on that one.

[woadiestyol]

Thanks! I noticed that the setParent command was in the video tutorial and the script itself, but it wasn't shown in the book - I think because it's not actually necessary in this case.

As for the eval thing, again, it seemed to work the same when I did it my way...and there doesn't seem to be a reason (that I can find) for why it's there. I would understand if it was used for the sake of example, but there wasn't really a description of what the "eval" command does, and since there's not much documented about it in the MEL command reference, I was a bit confused.

Anyways, the parent thing makes more sense to me now...I'm still not sure what "eval" is used for, but I don't seem to need it here, so I'll just accept my confusion for the time being.

[kiaran]

woadiestyol- I can't tell you why I used the eval command there. Maybe there was a reason, maybe not. It's been so long I don't remember. But if it works without, I wouldn't stress about it :)

As for 'eval' itself. It's a very handy command. Sometimes you need to build-up a long MEL command a peice at a time before executing it. For example, the curve command takes an argument for each vertex. So you can build up each vertex inside a loop like this:

//$allVertices is a list of vertices
string $cmd = "curve ";
for ($vert in $allVertices)
{
//Get vertex position
float $pos[] = `pointPosition $vert`;
//Add vertex to command
$cmd += ("-p " +$pos[0]+" "+$pos[1]+" "+$pos[2]);
}

//Now run the command to make a curve with the specified vertex positions
eval($cmd);

[woadiestyol]

Awesome, I think I get it - you're basically storing a long command into a variable $cmd, then using eval to run the command (since there could be a ridiculous number of verticies).

Thanks for the explanation! And, of course, thanks for the really awesome books - some of the best of any computer books I've ever read. The book is so great about explaining why things are done, not just how. I feel like I've already leaned so much, and i've got hundreds of pages to go.

So props to a great author and community - where else would I get direct answers from an author (believe me, I've tried)?

[ewerybody]

@woadiestyol: if you wanna know: eval runs commands. Most common use of eval is when you assemble each part of you command call and then want to evaluate it in one go. Something like:

string $cmd = "command -bla 3";
if ($bla)
$cmd = $cmd + " -zaozaaaa " + getNumberX($obj);
// you could even print it out to check it manually:
print ($cmd + "\n");
// then run the whole crp
eval($cmd);

EDIT:
oh.. already said ^^ good morning! *yaaaaaaaaaawn*
ok but there is evalDeffered as well. Sometimes it seems Maya does stuff before something different is finished. I you feel your stuff is executed a tick too early use evalDeffered and it will run the next time Maya goes idle.

When introducing to eval something might be importat: eval always uses global scope!!! So when trying to create arbitrary variables with eval they will be available in global scope a well! .. which is quite bad and actually a very stupid idea ( I had to find about that myself ... ;] )

okok, you won't use it now. Just to let you know.. ;]

[woadiestyol]

Cool, thanks for the tips!! I'll keep this in mind next time I'm writing a script using these commands.

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