Chapter 11: MEL Script

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Maya 8 at a Glance

• Chapter 11 MEL Script

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What is Scripting?

• Scripts are a series of commands that are
  interpreted line by line, rather than being
  compiled
• MEL exists inside Maya many of Mayas visual
  elements are driven by MEL
• Scripts can help optimize any stage of the
  production pipeline

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Creating and Running Scripts

• The Script Editor allows you to input lines of
  MEL script in order to be executed or saved
• Sourcing a script allows you to execute the
  contents of a saved MEL script
• MEL scripts can be saved to shelves for easy
  access

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Setting Attributes

• An attribute is an editable property that
  describes how an object looks or behaves
• Attributes can be set via the setAttr command

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Variable Rules

• Variable names must begin with a dollar sign
• Variable names can only include letters,
  numbers, and underscores
• The first character after the dollar sign cannot
  be a number
• Variables must be declared before they can be
  used

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Variable Types
Int
String
Float
Vector
Matrix
Array
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Looping

• Looping allows code to execute a specified
  number of times
• Good for repetitive work
• There are four types of loops
• For Loop
• For-In Loop
• While Loop
• Do-While Loop

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Listing Objects

• Often you need to list objects that are in the
  scene based on certain parameters
• The ls command lists all objects in the scene
• Flags such as ls selection and ls Boards can
  be specified to filter your list

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Branching

• Branching allows you to go separate paths in
  code based on an arbitrary true/false condition
• Ifelse statements are the most common way to
  create conditional logic in MEL
• Switch statements branches by comparing a
  control variable to cases
• Switches are ideal for when there are many
  possibilities based on the condition of a variable

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GUI Layout Options
Column
Row
Grid
Frame
Form
Scroll/Row
Tab/Form
Pane
Shelf
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GUI Control Options
Button
Canvas
Checkbox
Fields
Scroll
Slider
Radio button
Separator
Label
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Expressions

• Mathematical equations, programming commands,
  and MEL commands that can precisely control an
  objects motion
• Used in rigging and for motion that requires
  mathematical equations, such as a tire rotating
  based on the motion of a car

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