Maya MEL Programming

// scripts put here will be automatically loaded by Maya at launch time
~/maya/x.x/scripts

// Custom extra scripts folders could be added by updating bash env variable
set MAYA_SCRIPTS_PATH=$MAYA_SCRIPTS_PATH;<new_script_path>;

// An alternative way is to update Maya.env file with
MAYA_SCRIPTS_PATH = <new_script_path>;

// Retrieve the current Maya.env filepath location
string $envFile = `about -environnementFile`;

// userSetup.mel is being executed every time maya is started
// this can't be used to set the scene up

int $a = 65;
trace -where ("value : " + $a);
// returns 
// file: <filepath> line n : value : 65 

// 3 Mel command mode: create (default), query, edit
// <nodeType> <mode> <flags/values> -name <nodeName>
sphere -radius 4 -name mySphere;  // Create (default)
sphere -query -radius mysphere; // Query 
sphere -edit -radius 2 mySphere; // Edit
rename mySphere mySphere2; // Rename
delete mySphere; // Delete

source myMelFile.mel // reimport current myMelFile definition state

undo;

help(sphere)

int $myvar = 2;
sphere -edit -radius $myvar MySphere;

// Int & Float
int $myInt = 2;
float $myFloat = 2.0;

// String
string $myString = "Hello World\n";
int numChars = size($myString);

// Vector
vector $myVector = << 10.0, 2.0, 3.0 >>; 
// update x axis value as follow
vector $myVector = << 15.0, $myVector.y, $myVector.z >>; 
move -absolute ($myVector.x) ($myVector.y) ($myVector.z);
print ($myVector.x);

// Array
int $myIntArray[] = {2, 5, 8}; // more efficient to provide array size at creation time
string $myStrArray[3] = {"hello", "world", '!'}; 
vector $myVecArray[2] = {<< 10.0, 2.0, 3.0 >>, << 10.0, 5.0, 3.0 >>};
float $myFloatArray[3] = {2.5, 5.0, 8.1};
print ( $myFloatArray[0], size($myFloatArray) );

// dynamic array resizing
int $vals = [];
$vals[0] = 2;
$vals[4] = 4;
print ( $vals ) // returns 2 0 0 4

// appending to array
$myStrArray[ size($myStrArray) ] = "\nYea";

// deleting array content
clear( $myStrArray );

// Matrices
matrix $myMatrix[2][4] = << 3,8,9,7; 5,4,3,2 >>;
print ( $myMatrix[0][0] );
float $topTransformMtx[] = `xform -query -matrix topTransform;` // retrieve topTransform node's matrix as a float values list

// Boolean
bool_true = on; // => true
bool_true = true; // => true
bool_true = yes; // => true

bool_false = off; // => false
bool_false = false; // => false
bool_false = no; // => false

int $a, $b;

$b = $a = 50;

$a/=1;
$a+=1;
$a-=1;
$a*=1;

$a++;
$a--;

float $myNodeScale = `getAttr myNode.scale`; // store scale info in $myNodeScale var

vector  $tmp = << 1.0, 0.0, 0.0>>;
setAttr myNode.scale ($tmp.x) ($tmp.y) ($tmp.z);

/* Create */
addAttr -longName "mySlider" -attibutType long -min 0 -max 10 -defaultValue 0 myNode; //create a slider

if (!attributeExists ("id", myNode)) {
    addAttr -longName "id" -attibutType long myNode;
}

/* Read */
listAttr myNode; // list all attributes
listAttr -userDefined myNode; // list all custom attributes
listAttr -keyable myNode; // list all keyable attributes

/* Update */
setAttr -keyable true myNode.mySlider;

/* Delete */
deleteAttr myNode.mySlider; //delete attr

int $a = 10;

if ( $a < 10) {
	print "a is lower than 10";
}
else if ($a == 10) {
	print "a is equal to 10";
}
else {
	print "a is higher than 10";
}

int $a = 10;

switch ($a) {
    case 1:
        print "a == 1";
        break;
    case 2:
        print "a == 2";
        break;
    default:
        print "a is not in equal to either 1 or 2";
        break;
}

int $a = 10;
$equal_ten = ($a == 10) ? true : false; 

int $elems[3] = { 10, 5, 2 };
int $index;

for ($index=0; $index < size($elems); $index++ ) {
    print ( $elems[$index] );
}

int $elems[3] = { 10, 5, 2 };
int $elem;

for ($elem in $elems ) {
    print ( $elem );
}

warning "Incorrect parm, it will be ignored!";
error "Error, illegit value";

if (!`exists myProcedure`)
    error "Error, Couldn't find myProcedure. Please install it"
else 
    // returns the filepath where the procedure comes from
    `whatIs myProcedure`;  // whatIs could also be used to retrieve variable's type

int $a = 10;
whatIs "$a"; // returns int variable

proc int test (int $input){
	if ($input == 1) {
		return 1;
	}
	return 0;
}

int $err = catch( eval("source foobar") ) // return 1 if an error was raised

float $currentFrame = currentime -query; //retrieve current frame
currentTime 2; // set current frame to be the #2 
currentTime 2sec; // compute and place the current frame to be on 2sec 

listAnimatable myNode; // retrieve all keyable attributes
keyframe -query -name myNode; // retrieve myNode keyframed attributes
keyframe -query -name myNode.translateY; // retrieve myNode.translateY keyframes
keyframe -query -time 2 -eval myNode.translateY; // retrieve myNode.translateY keyframes at frame 2 without evaluating DAG
getAttr -time 2 myNode.translateX; // retrieve x translate value at frame 2 (getAttr with -time could induce DAG eval)
play; // play the frame range

setKeyframe -time 2 -value 2 myNode.translateY; // set a keyframe at frame 2
setKeyframe -time 4 -value 4 myNode.translateY; // set a keyframe at frame 2
setKeyframe -insert -time 3 myNode.translateY; // insert a keyframe at frame 3 without changing the curve shape
keyframe -edit -time 4 -valueChange 10 myNode.translateY; // update keyframe value

ls  // list all nodes
ls -type surfaceShape // list all surface shape nodes
ls -selection // list currently selected nodes
ls -clear // cancel selection

listRelatives parentNode; // list all child nodes, extra flags could be used to filter out result
listRelatives -parent childNode; // retrieve parent nodes
listRelatives -shapes node; // retrieve shapeNode

select -r mySphere; // select a node

group -name topTransform mySphere; // create a new transform node and parent the node to it. Transformation applied to topTransform will also affect mySphere
parent mySphere2 topTransform; // make mySphere2 a child of topTransform and applied transforms
inherit Transform -off MySphere2; // Disable parent tranforms inheritance for MySphere2

/* Transform Objects: */

// -relative or -absolute flags could be used
move -relative 1 0 0 topTransform; // Translate topTransform and its childrens
scale -absolute 10 2.3 3 MySphere2;// Scale MyShere2
rotate -relative 90deg 0 0 topTransform; // Rotate topTransform and its childrens

xform -relative -translation 0 5 -6 -scale 0.5 0 0 -rotation 90deg 0 0 topTransform; // Do all operation at once

// transform every selected node per 1 on y axis
$nodes = `ls -selection`;
for ($node in $nodes) {
    setAttr ($node + ".translateY") (1.0 + `getAttr $node.translateY`)
}


/* Move an object along a curve: */
pathAnimation -curve testCurve myNode;

joint; // create joint1 under the currently selected obj (might wanna do a ls -clear before) 
joint -position 0 1 0;  // create joint2 under joint1 at given position
insert joint1; //create a new joint under joint1 instead of joint 2 as the joint command would have

joint -edit -relative -position 0 5 0 joint2; // edit joint2 position to be 0 5 0 from its parent joint3
joint -query -degreeOfFreedom joint3; // return axis that could be edited
joint -edit -degreeOfFreedom "y" joint1; // limit joint1 movement to y axis only

joint -query -limitY joint1; // retrieve current min/max possible values for edition (-360; 360);
joint -edit -limitY 0deg 180deg joint1; // limit rotation value on Y axis from 0-90 degrees
joint -edit -angleY 50deg joint3; // rotate joint3 relatively to its parent
rotate 0 90deg 0 joint2; // rotate joint2 with an absolute rotation

removeJoint joint2; //delete joint



/* rescale skeleton: */

proc rescaleSkeleton ( string $inputNode, float $outputScale) {
    
    string $jointNodes = `listRelatives -fullPath -children -type joint -allDescendents $inputNode`;

    for ($jointNode in $jointNodes) {
        // retrieve current joint position, edit it and update it
        float $currentJointPosition = `joint -query -relative -position $jointNode`;

        $currentJointPosition[0] *= $outputScale;
        $currentJointPosition[1] *= $outputScale;
        $currentJointPosition[2] *= $outputScale;

        joint -edit -position $currentJointPosition[0] $currentJointPosition[1] $currentJointPosition[2]  $jointNode;
    }
}
--------------------------------

/* Retrieve joints position: */

proc printJointsTransform(string $inputNode, string $spaceFlag) {
    /*
    $inputNode is the skeleton root node
    $spaceFlag is either '-worldSpace' or '-objectSpace'
    */

    $jointNodes = `listRelatives -fullPath -children -type joint -allDescendents $inputNode`;
    
    for ($jointNode in $jointNodes) {
        // retrieve current joint transform and print it
        float $trans [] = `xform $spaceFlag -query -translation $jointNode;`
        float $rot [] = `xform $spaceFlag -query -rotation $jointNode;`
        float $scale [] = `xform $spaceFlag -query -scale $jointNode;`

        print ("\n Joint: " + $jointNode);
        print ('\n Translation: ' + $trans[0] + ' ' + $trans[1] + ' ' +  $trans[2]);
        print ('\n Rotation: ' + $rot[0] + ' ' + $rot[1] + ' ' +  $rot[2]);
        print ('\n Scale: ' + $scale[0] + ' ' + $scale[1] + ' ' +  $scale[2]);
    
    }

}

// Simple window connecting attr of a node to some parm
// source: https://www.asc.ohio-state.edu/price.566/courses/694/cntrlConnections.html


{
    string $node [] = `sphere`;
    window -title "1st way node parm binding" testWindow;
        panelLayout -configuration "horizontal2";
        columnLayout;
            attrFieldGrp -attribute $node[0] + ".translate" -label $node[0] + "_translate";
            attrFieldGrp -attribute $node[0] + ".rotate" -label $node[0] + "_rotate";
            attrFieldGrp -attribute $node[0] + ".scale" -label $node[0] + "_scale";
            setParrent ..;
  
}
///////////////////////////////////////////////////

{
    string $nodes [] = `ls -selection`;
    string $node = $nodes[0];
    //deleteUI testWindow2;
    
    window -title "2st way individual node parm binding" testWindow2;
        columnLayout;
            floatFieldGrp -label "Translate" -numberOfFields 3 translation_field;
            
            // connect fields to attr, all 3 parms needs to be plugged to work
            connectControl -index 1 translation_field ($node + ".tx");
            connectControl -index 2 translation_field ($node + ".ty");
            connectControl -index 3 translation_field ($node + ".tz");
    
    showWindow testWindow2;
    
}

/* Type object: */

$obj = `ls -selection`;
objectType $obj; // returns node type
--------------------------------

/* Check if object exists: */

objectExists nurbs1; // returns 1 if nurbs1 exists, 0 otherwise
--------------------------------

/* Find operating System and Versioning: */

float $mayaVer = float(`about -version`);
string $opSys = `about -operatingSystem`;
--------------------------------

    - Complete Maya Programming, David A. D. Gould (2003)
    - https://www.asc.ohio-state.edu/price.566/courses/694/