Maya summary

Summary of elementary Maya feature.
Resource
Shortcuts
Camera
alt + left click | Rotate |
alt + middle click | Strafe / pan |
alt + right click | Zoom |
F | Focus on selection |
Views
Other
S | Insert key frame |
Architecture
Maya works on nodes. Nodes have attributes which we connect together using MEL or Python scripts.
Maya GUI calls those script to setup the nodes.
MEL script
Manual
Bookmark the MEL reference manual of whatever Maya version you are using. Once you get an understanding of MEL scripting this is the go to page to find all MEL built-in commands.
Useful resources
http://ewertb.soundlinker.com/maya.php
MEL syntax (quite good and concise):
http://nccastaff.bournemouth.ac.uk/jmacey/OldWeb/RobTheBloke/www/
Syntax
Variables are always prefixed with '$' when declared and used:
int $myInt = 0; string $helloString = "hello"; print( $helloString + " " + $myInt ); // outputs: 'hello 0'
Declaring arrays:
int $myArray[] = {1,3,9};
for loops (notice we don't declare the types):
for( $i=0, $j=0.0; $i<10; ++$i, $j+=0.75 ){ print($j + ", "); } // outputs: '0, 0.75, 1.5, 2.25, 3, 3.75, 4.5, 5.25, 6, 6.75,'
Iterate over array elements:
int $myArray[] = {1,3,9}; for($i = 0; $i < size($myArray); ++$i) print($myArray[$i] + ", "); // outputs: '1, 3, 9,' // Alternatively: for( $element in $myArray) print($element + ", ");
MEL arrays are dynamic
int $myArray[] = {1,3,9}; $myArray[9] = -1; for($i = 0; $i < size($myArray); ++$i) print($myArray[$i] + ", "); // outputs: 1, 3, 9, 0, 0, 0, 0, 0, 0, -1,
Array /multi attributes
Maya nodes contain attributes (access through 'plugs' in c++/python API). When an attribute holds an array we also call it a multi attribute or array attribute.
Multi attributes can be thought as a map (e.g. map<unsigned (connection idx), Type (value)>
):
attribute[3] (value) : [ elt1, elt2, elt3] Logical indices (key): { 0, 2, 9} // indices displayed in 'Node Editor' Physical indices : { 0, 1, 2} // Always consecutive
Look up an attribute's connection and list the logical indices of the connection:
string $node_names[] = `listConnections ($source_node+".attribute_name")`; // example output: {'node1', 'node2'} int $connection_indices[] = `getAttr -multiIndices ($source_node+".attribute_name")`; // example output: {0, 4} // Loop through the nodes connected to the attribute '$source_node+".attribute_name[]"' for( $i = 0; $i < size($node_names); ++$i) { int $idx = $connection_indices[$i]; string $name = $node_names[$i]; }
How to describe an attribute / plug:
string $plug_name = "some_node_name.some_attr_name[index_atrr].some_compound_name"
Check connection at index:
Is a source {array} attribute currently connected to a node?
This can be use to determine if an index of an array attribute is free and can be safely connected with connectAttr()
.
string $con = `connectionInfo -sourceFromDestination ("some_node_name.some_attribute[index]")`; if( size( $con ) == 0){ /* Yea I'm free */ }
Find first available connection (maya doc):
maya2014/scripts/AETemplates/getNextFreeMultiIndex.mel source "getNextFreeMultiIndex.mel" // N.B: no need to define index with [idx] string $attribute_name = "some_node_name.some_attr_name"; // index from which we start looking up the array attribute. int $start_idx = 0; getNextFreeMultiIndex(attribute_name, start_idx);
Remove element at index:
// This will remove the element with index 4 from the input of // the choice node as long as there are no incoming or outgoing // connections to the attribute. removeMultiInstance choice.input[4]; // This will remove the element with index 100 from the input of // the choice node, breaking any existing connections first. removeMultiInstance -b true choice.input[100];
c.f maya2014/scripts/AETemplates/AEnewNonNumericMulti.mel and AEremoveMultiElement()
Get the size of the array attribute:
getAttr -size "some_node_name.some_attribute" // N.B: no need to define index with [idx]
List the currently used attribute:
listAttr -multi $plug_name
Source of inspiration to understand how to handle multi-attributes:
maya2014/scripts/AETemplates/AEnewNonNumericMulti.mel
Check out functions like: AEnewNonNumericMultiAddNewItem(), AEremoveMultiElement()
Mesh
Get number of vertices of a mesh:
polyEvaluate -v "pCylinder1Shape";
C++ API
Introduction
Every data (DAG nodes, lights etc.) are represented as MObject in Maya. Instead of converting the MObject to some specialized type we use function sets MFnXxx(). To access the methods of a specialized type we must use a function set:
MFnAttribute attribute( mObject ); // bind object to functions attribute.name(); // use object's functions // We can also bind the function set like so: attribute.setObject( mObject );
Basics:
Display information in Maya script console: MGlobal::displayInfo("some infos");
Look up the DAG (scene tree), you can start from an arbitrary node with reset, use breadth or depth first order and check the current depth of the iterator (0 for root):
MItDag aItDag(MItDag::kDepthFirst); aItDag.reset(iNode.mDagPath.node(), MItDag::kDepthFirst); for(; !aItDag.isDone(); aItDag.next()) { MDagPath aDagPath; aItDag.getPath(aDagPath); MFnDagNode fnNode( aDagPath ); // Get the DAG node MString str = fnNode.typeName(); // Get its type for instance "transform" or "joint" aItDag.depth();// Depth in the scene tree }
Alternate way to look up the scene tree:
void rec_tree(const MFnDagNode& fnNode) { for(unsigned i = 0; i < fnNode.childCount(); ++i) { MObject obj = fnNode.child( i ); ret_tree(obj); // Sometimes this conversion fails between MFnNode and MObject wherase the dag iterator works well TODO: search why. } return; }
Fetch attribute value of a node:
MFnDependencyNode fn( dagPath ); // get the MPlug for the tx attribute MPlug plug = fn.findPlug("tx"); // get the value from the plug float tx; plug.getValue(tx);
Custom nodes: Construction: Never call Maya API in the custom node. Instead override the method: postConstructor() Destruction: When removing a node with deleteNode the key stroke del etc. you only remove the node from the dependency graph and the node is placed onto the undo list. The destructor will not be called unless the node disappear from the undo list (list flush/overflow, new scene) Removal from the dependency graph can be detected with various callbacks, see: MDGMessage:: MNodeMessage::addNodeAboutToDeleteCallback etc.
Python API
Mostly resemble the C++ API. There are two python APIs:
#Old from maya.OpenMaya import * # Python API 2.0 from maya.api.OpenMaya import *
Be sure to not mix them up (especially when looking for documentation they are very similar) and use the latest one for new code.
Tricks
Quick way to check environment variables (PATH, MAYA_PLUGIN_PATH etc)
import sys for elt in sys.path: print(elt) import os, pprint pprint.pprint(dict(os.environ), width = 1)
Maya math nodes
plusMinusAverage math node specification. Originally designed with shaders in mind those operations work on vectors, i.e. addition, division etc is usually applied on a per component basis (out.x = in1.x + in2.x), (out.y = in1.y + in2.y) etc.
Note: when disconnecting make sure to reset the value of the attribute, otherwise it will keep adding, subtracting etc. whatever was the value at disconnection. |
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divideMultiply math node specification.
NO OPERATION: |
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condition math node specification. Compare 'firstTerm' and 'secondTerm' with some boolean operator (<,>,== etc.) OutColor is assigned ColorIfTrue or ColorIfFalse according to the result of the operation.
if( firstTerm operation secondTerm ){ OutColor.r = ColorIfTrue.r OutColor.g = ColorIfTrue.g OutColor.b = ColorIfTrue.b } else { OutColor.r = ColorIfFalse.r OutColor.g = ColorIfFalse.g OutColor.b = ColorIfFalse.b } |
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BlendColors math node specification. Linear interpolation between Color1 and Color2 given the parameter \( blender \in [0.0, 1.0]\).
Output = Color1.rgb * (1.0 - blender) + Color2.rgb * blender |
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Reverse math node specification. Reverse a parametric parameter: Output = 1.0 - Input
.
Output.x = 1.0 - Input.x Output.y = 1.0 - Input.y Output.z = 1.0 - Input.z |
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Note: always prefer 'remapValue' which is really fast to evaluate contrary to the 'animCurve' node.
OutputValue = Curve( InputValue ) Where the function "float Curve(float)" is the curve displayed in the attribute editor and which control points are stored in the "Value[]" attribute; OutputColor.RGB = Gradient( InputValue ) Where the function "Vec3 Gradient(float)" is the gradient strip displayed in the attribute editor and which interpolated colors are stored in the "Color[]" attribute |
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Matrices
Official list of built in matrix nodes
Multiplication order, from right to left as we increase the index:
Indices: n ... 1 0 Matrix : mat_n * ... * mat_1 * mat_0
TODO: addMatrix, aimMatrix, blendMatrix, composeMatrix, decomposeMatrix, fourByFourMatrix, holdMatrix, passMatrix, pickMatrix, uvPin, proximityPin
\( MatrixSum = \prod_{i=n}^{0} MatrixIn[i] \)
MatrixSum = MatrixIn[n] * ... * MatrixIn[1] * MatrixIn[0] |
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\( MatrixSum = \sum_{i=n}^{0} WtMatrix[i].MatrixIn * WtMatrix[i].WeightIn \)
MatrixSum = WtMatrix[n].MatrixIn * WtMatrix[n].WeightIn * ... * WtMatrix[0].MatrixIn * WtMatrix[0].WeightIn * WtMatrix[0].MatrixIn * WtMatrix[0].WeightIn |
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Extra nodes in 'matrixNodes.mll' plugin:
- inverseMatrix node
- transposeMatrix node
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