2009
Table Of Contents
- Contents
- Overview
- Maya Basics
- Polygonal Modeling
- Introduction
- Preparing for the lesson
- Lesson 1: Modeling a polygonal mesh
- Introduction
- Setting modeling preferences
- Using 2D reference images
- Creating a polygon primitive
- Modeling in shaded mode
- Model symmetry
- Selecting components by painting
- Selecting edge loops
- Editing components in the orthographic views
- Editing components in the perspective view
- Drawing a polygon
- Extruding polygon components
- Bridging between edges
- Adding polygons to a mesh
- Splitting polygon faces
- Terminating edge loops
- Deleting construction history
- Mirror copying a mesh
- Working with a smoothed mesh
- Creasing and hardening edges on a mesh
- Beyond the lesson
- NURBS Modeling
- Subdivision Surfaces
- Animation
- Introduction
- Preparing for the lessons
- Lesson 1: Keyframes and the Graph Editor
- Lesson 2: Set Driven Key
- Lesson 3: Path animation
- Lesson 4: Nonlinear animation with Trax
- Introduction
- Open the first scene for the lesson
- Creating clips with Trax
- Changing the position of clips with Trax
- Editing the animation of clips
- Reusing clips within Trax
- Soloing and muting tracks
- Scaling clips within Trax
- Open the second scene for the lesson
- Creating clips from motion capture data
- Extending the length of motion capture data
- Redirecting the motion within a clip
- Beyond the lesson
- Lesson 5: Inverse kinematics
- Introduction
- Open the scene for the lesson
- Understanding hierarchies
- Viewing hierarchies using the Hypergraph
- Creating a skeleton hierarchy
- Parenting a model into a skeleton hierarchy
- Applying IK to a skeleton hierarchy
- Creating a control object for an IK system
- Constraining an IK system
- Limiting the range of motion of an IK system
- Simplifying the display of a hierarchy
- Applying parent constraints on an IK system
- Planning an animation for an IK system
- Animating an IK system
- Beyond the lesson
- Character Setup
- Polygon Texturing
- Rendering
- Introduction
- Preparing for the lessons
- Lesson 1: Rendering a scene
- Introduction
- Open the scene for the lesson
- Creating shading materials for objects
- Refining shading materials for objects
- Maya renderers
- Rendering a single frame using IPR
- Rendering using the Maya software renderer
- Batch rendering a sequence of animation frames
- Viewing a sequence of rendered frames
- Beyond the lesson
- Lesson 2: Shading surfaces
- Lesson 3: Lights, shadows, and cameras
- Lesson 4: Global Illumination
- Lesson 5: Caustics
- Dynamics
- Painting
- Introduction
- Preparing for the lessons
- Lesson 1: Painting in 2D using Paint Effects
- Lesson 2: Painting in 3D using Paint Effects
- Introduction
- Preparing for the lessons
- Brushes and strokes
- Rendering Paint Effects strokes
- Paint Effects on 3D objects
- Creating a surface to paint on
- Painting on objects
- Using turbulence with brush stroke tubes
- Using additional preset brushes
- Mesh brushes
- Converting mesh strokes to polygons
- Modifying a converted polygonal mesh
- Beyond the lesson
- Lesson 3: Painting textures on surfaces
- Expressions
- Scripting in Maya
- Index
Using runtime expressions
There is one other type of expression you can create for a particle object (shape
node)—a runtime expression. By default, a runtime expression executes each
frame during playback. A runtime expression does not execute when you go
to the start time (or at the time in which a particle is emitted).
You’ll often create both types of expressions for a particle object—a creation
expression that initializes an attribute value in the first frame, and a runtime
expression that controls the attribute value in subsequent frames.
The following steps show how to create a runtime expression to change particle
color during playback.
To create a runtime expression
1 In the Per Particle (Array) Attributes section of the Attribute Editor,
right-click the rgbPP box and select Runtime Before Dynamics Expression
from the pop-up menu.
2 Enter this runtime expression:
BubblesShape.rgbPP = sphrand(1);
3 Click the Create button to compile the expression.
4 Play the animation.
The particles flicker in random colors as the animation plays back. The
runtime expression controls the rgbPP attribute during playback. Because
rgbPP is a per particle attribute, the runtime expression executes for each
particle in the object for each frame. For each particle, the expression
assigns the rgbPP attribute the output from the execution of the sphrand
function with an argument of 1. The sphrand function is one of Maya’s
many built-in mathematical functions that are useful in expressions.
The sphrand function with an argument of 1 assigns each particle’s rgbPP
color a random vector. The vector represents a random point in a spherical
Using runtime expressions | 587