2011
Table Of Contents
- Autodesk Composite 2011 User Guide
- Contents
- Preface
- Getting Started
- Reference
- About Reference
- Projects
- Wiretap
- Importing Media
- Getting Familiar with Your Workspace
- The Player
- About the Player
- Player View Default Settings
- Setting the Target
- Setting Context Points
- Playing Back in Multiple Views
- Playback Performance
- Setting the Target for the Player
- Setting the Channels for the Target
- Setting the Mark In and Mark Out Points for Playback
- Setting the Repeat Mode
- Setting the Frame Rate for Playback
- Setting the Real-Time Playback Preference
- Synchronizing or Separating Playback between Views
- Setting the Playback Point when the Player Updates
- Setting the Resolution for a Player
- Setting the Grid in the Player
- Setting a Region of Interest (ROI) in the Player
- Displaying Masks and Guides
- Showing or Hiding Tiles
- Turning Hardware Rendering On or Off
- Setting the Pixel Aspect Ratio of the Player
- Displaying Player Option Information in the Player view
- Displaying Manipulators in the Player
- In-player Pixel Display
- Adjusting the Zoom or Pan
- Applying a LUT or Color Conversion Tool to the Player
- The Mini-Player
- The Fullscreen Player
- Working with Compositions
- Multilayer Compositing and 3D Effects
- Reaction Compositing and Effects
- Compositing Workflow
- Basic Compositing in Reaction
- Working with Maya Pre-Comps
- Working with Layers
- Working with Geometric Surfaces
- Using Parenting Axes
- Working with Materials
- Working with Lights
- Working with Cameras
- Camera Mapping
- 3D Displacement
- Transforming Objects
- Reaction Rendering Effects and Output Results
- Setting up a Stereo Camera Rig
- Pre-Compositing
- Importing FBX Files
- Premultiplication
- 2D Compositing
- Image Processing Tools
- Pixel Expressions
- Warping
- Effects Tools
- Managing Film Grain
- Pulling Keys and Creating Mattes
- Masking
- Raster Paint
- Vector Paint
- Color Correction
- About Color Correcting
- Applying LUTs
- Working with ASC CDLs
- Broadcast Safe Tool
- Transforming Color Space with the Log and Delog Tools
- Color Correcting with CC Basics
- CC Histogram
- Clamp Color Tool
- Color Space Tool
- Processing Images with Photo Lab
- Inverting an Image
- Remap Color
- Set Fill Color
- Solarizing an Image
- Creating a Monochrome Image
- Modifying a Display With the Pass Through Tool
- Setting the Amount of Gray in an Image
- Converting an Image to sRGB
- Animation
- Animation Concepts
- The Animation Tab
- Composition Browser
- Animation Editor
- The Animation Property Area
- Player Controls
- Working with Cue Marks
- Contextual Menus
- Keyframing Workflows
- Marking Attributes for Keyframing
- Setting Keys Manually
- Setting Keyframes Automatically
- Editing Keyframes in the Tool UI
- Editing Keyframes in the Animation Editor
- Adding and Deleting Keyframes
- Modifying Interpolation
- Modifying Extrapolation
- Temporarily Modifying Attribute Values
- Customizing the Layout when Working with Animation Curves
- Global Time vs. Local Time
- Time Offsets, Keyframing, and Instancing
- Time Tools
- Customization Tools
- Vectors
- Expressions
- About Expressions
- Short Expressions
- Expression Input Paths
- Visual Linking
- Visual Linking Methods
- Navigating the Expression String
- Validating and Applying the Expression String
- Viewing the Expression
- Associating Comments with an Expression
- Editing an Expression
- Removing an Expression
- Setting Expressions Examples
- Expression Reference Tables
- Arithmetic Operators
- Comparison Operators
- Operator Precedence
- Math Functions
- Vector Functions
- Random Number Functions
- Rounding Functions
- Trigonometric Functions
- Constants
- Time Functions
- Profile Functions
- Conditional Functions
- Tracking and Stabilizing
- About Tracking and Stabilizing
- Tracking Concepts
- Stabilizing Concepts
- Tracker UI
- Tracking Workflow
- Choosing a Reference Point
- Positioning the Reference Box
- Resizing the Reference and Tracker Boxes
- Resetting the Reference Box
- Resetting the Tracker Box
- Changing the Color of a Tracker
- How the Tracker Works
- Tracking Position
- Tracking the Scale of an Object
- Tracking the Rotation of an Object
- 4-Point Tracking
- Tracking Difficult Shots
- Correcting Errors
- Stabilizing
- 1-point Stabilizing
- 2-point Stabilizing
- Simultaneous Stabilizing and Tracking
- Video Tools
- Utilities
- Hotkeys
- Composite Executables
- Python Scripting
- Initialization Variables and String Substitutions
- Glossary
- Index
consider premultiplying two or more images whenever you have to perform
a color correction or use filtering nodes.
When you premultiply an image by a matte, you should be aware that there
is a very specific brightness relationship between the pixels in the color
channels and the pixels in the matte. Since certain systems that will assume
that you are working with unpremultiplied systems, will also assume this
brightness relationship. As such, the brightness of any color channel cannot
be modified without also impacting the alpha channel.
There are two general rules to remember when considering premultiplication:
1 Only color correct unpremultiplied images.
2 Only apply filter and transform nodes to premultiplied images.
Common Problems with Premultiplication
There are certain problems that can occur when the rules of premultiplication
are ignored. These can range from problems with edges to raised global levels.
Additionally, when the premultiplied state of an image is ignored, there may
also be unwanted fringing around a masked object or the unwanted side effects
that may occur when a node affects parts of an image that it should not.
A possible result of compositing with a premultiplied image would be slight
lightening or darkening of the composite areas where the foreground matte
is semitransparent.
Another common problem is when color correction has been applied to a
foreground premultiplied image. This could result in the blacks in the scene
being elevated above the value of 0, which means that even though the matte
channel may still specify that the surrounding field is in black, the RGB
channels may have some small, often visually undetectable value.
Premultiplication Tools
Composite includes two tools for the purpose of premultiplication functions:
the Premultiply tool and the Unpremultiply tool. The Premultiply tool
premultiples an input image (see
Premultiply Tool on page 413). The
Unpremultiply tool unpremultiplies an input image (see
Unpremultiply Tool
on page 414).
338 | Chapter 15 Premultiplication