topic Re: Pass array of arguments into command in Maya Programming Forum

Pass array of arguments into command

bphoenix22YC2 — Sat, 12 Feb 2022 00:37:54 GMT

Hey folks, I'm new to Mel here so please excuse the beginner question. I'm writing a simple script to run polySeparate on the user's actively selected shells (returned from polyEvaluate).

What I'm stuck on is that I'm not able to get the -sss argument to accept a list, it seems to need an explicit index (or an explicit int more accurately). Looking at the output of the command executed manually, it adds a separate -sss flag for each selected shell, and each argument is a separate int. Since I want to run this command on all of $shells[], entering them separately obviously won't work. I haven't found a solution to this so far in the documentation, but I may be looking in the wrong way.

The following script will return an error, but if I replace $shells[] with $shells[0] it executes correctly, though not as I intend.

// Separate selected shells { int $shells[]; $shells = `polyEvaluate -as`; string $a[]; $a = `polySeparate -sss $shells[] Bone_1_Start_Mesh`; print($a); }

Thanks in advance for any help!

P.S. Bone_1_Start_Mesh is just a test object, but will be replaced with a variable.

Re: Pass array of arguments into command

Kahylan — Tue, 15 Feb 2022 01:17:19 GMT

Hi!

Flags in MEL can't change type, if they are designed to take a single value, they will only take a single value, if they are designed to take an array with 3 values they will only take an array with 3 values.

You can however, loop through your values like this:

{ int $Shells[]; $Shells = `polyEvaluate -as`; string $a[]; string $obj = "pCube1"; for($s = 0; $s < `size $Shells`; $s++){ print($s); $a = `polySeparate -sss ($Shells[$s]-$s) $obj`; $obj = $a[1]; } }

I had to introduce the Mesh to separate from as it's own variable (in my case "pCube1" in yours "Bone_1_Start_Mesh"), since this value changes when the mesh gets separated. Also I had to indicate the shell that was separated as ($Shells[number of loop] - number of loop) because with every polySeparate the Shell ID drops by 1, since there is one Shell less in the Object.

I hope this helps!

Re: Pass array of arguments into command

BurkhardRammner — Tue, 15 Feb 2022 12:31:53 GMT

The correct way of doing what you want here is to create a string with your command, then evoking it using eval:

int $shells[] = polyEvaluate( "-as" ); string $sel[] = ls( "-sl" ); if( size($shells) && size($sel) ) { string $obj = plugNode( $sel[0] ); string $c = "polySeparate "; for( $i=0; $i<size($shells); $i++ ) {$c+=" -sss "+$shells[$i]+" ";} $c+=$obj; evalEcho( $c ); }

Re: Pass array of arguments into command

bphoenix22YC2 — Wed, 16 Feb 2022 15:37:11 GMT

Thanks Kahylan! This seems to work, though it is sort of the case I was hoping to avoid by passing a simpler argument. Seems like Mel isn't well set up for that unfortunately. I've had a lot of trouble with the polySeparate command being convoluted in general (as you mentioned, the object gets renamed, and there isn't a distinction in the output between the original and new meshes), and as a result I've reimplemented this in my script by duplicating the object entirely with a selection set, inverting the selection and deleting. It ends up seeming to be much simpler.

Re: Pass array of arguments into command

bphoenix22YC2 — Wed, 16 Feb 2022 15:40:05 GMT

Thanks Burkhard! I wasn't aware of the echo command, but it seems helpful more generally as well, so I appreciate the tip.