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Apple MA434Z/A User Manual - Page 422

In a Nutshell—the Rules of Premultiplication, Problems Caused When Premultiplication Is Ignored

UPC - 885909104239

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Shake takes a third approach, giving you explicit control over premultiplication for every image in your composition. Although this can be inconvenient, it helps you get around the problems that are typical in other software packages. In a Nutshell-the Rules of Premultiplication If you don't read the full explanation of the mathematics of premultiplication, here are the two rules you must always follow when creating a composition in Shake: • Rule Number 1: Always color correct unpremultiplied images. To unpremultiply an image, use a Color-MDiv node. • Rule Number 2: Always filter and transform premultiplied images. To premultiply an image, use a Color-MMult node. Problems Caused When Premultiplication Is Ignored There are two typical problems that occur when the premultiplied state of an image is ignored: • Unwanted fringing around a masked subject • Unwanted side effects that occur when a node affects parts of the image that ought not to be affected The following exercise demonstrates these problems. To experience the heartbreak of premultiplication errors: 1 Open the Image tab, and click the FileIn node. The File Browser opens. 2 In the File Browser, navigate to the directory where you copied the tutorial media. The default path is $HOME/nreal/Tutorial_Media/Tutorial_Misc/premult. 3 Select the bg.jpg and munch_pre.sgi images, then click OK. The nodes appear in the Node View. The image munch_pre.sgi, rendered in Maya, is premultiplied (the blacks in the alpha match the blacks in the RGB), and has an embedded alpha channel. munch_pre.sgi munch_pre.sgi, alpha channel bg.jpg Images from Munch's Oddysee courtesy of Oddworld Inhabitants. 422 Chapter 15 Image Processing Basics

Section	Page
Shake 4 User Manual	1
Contents	5
Shake 4 Documentation and Resources	15
What Is Shake?	15
Using the Shake Documentation	16
User Manual	16
Tutorials	16
Onscreen Help	16
Viewing Shake Onscreen Documentation on Linux Systems	16
Contextual Help	17
Apple Websites	17
Shake Websites	18
Keyboard and Mouse Conventions on Different Platforms	18
Using a Stylus	19
Window Navigation Using a Stylus	20
Using Dual-Head Monitors	20
Part I: Interface, Setup, and Input	21
An Overview of the Shake User Interface	23
Opening Shake	23
Opening Two Scripts at Once	23
Overview of the Shake User Interface	24
Getting Help in Shake	26
Making Adjustments to the Shake Window	27
Navigating in the Viewer, Node View, and Curve Editor	28
Saving Favorite Views	28
Working With Tabs and the Tweaker	30
Using the Tweaker	30
OS Window Functions	31
Menus and the Title Bar	31
Title Bar Information	31
Shake Menu (Mac OS X Only)	32
File Menu	32
Edit Menu	34
Tools Menu	34
Viewers Menu	35
Render Menu	35
Script Management	35
Customizing AutoSave	36
Changing the Possible Levels of Undo	37
The File Browser	38
Opening the File Browser	38
Navigating in the File Browser	39
Adding Directories to the Favorites List	40
Selecting Files	41
Viewing Controls	42
Specifying Media Placement	44
Additional Controls for Image Output	44
Using and Customizing Viewers	45
Using Multiple Viewers	46
Looking at Images in a Viewer	50
Suspending Rendering and Viewer Redraw	52
Controls in the Viewer Shelf	52
Using the Compare Buffers	57
Viewer Lookups, Viewer Scripts, and the Viewer DOD	61
Using the Viewer’s Domain of Definition (DOD)	67
Creating Your Own VLUTs and Viewer Scripts	68
Viewer Keyboard Shortcuts	68
The Viewer Shortcut Menu	69
Node-Specific Viewer Shelf Controls	70
The Parameters Tabs	72
Accessing a Node’s Controls Using the Parameters Tabs	72
Using Tweaker Windows	74
Global Parameters	74
Adjusting Parameter Controls	74
Using Expressions in Parameters	78
Linking One Parameter to Another	79
Combining Links With Expressions	79
Displaying Parameter Values in the Viewer	80
Copying and Pasting Script Code in Shake	80
The Parameters Tab Shortcut Menu	81
The Domain of Definition (DOD)	82
Assigning a DOD	83
Keying, Color Correcting, and the Background Color	85
The Time Bar	88
Setting a Script’s Frame Range	88
Playback Controls	89
Previewing Your Script Using the Flipbook	90
Setting a Script’s Global Parameters	91
About Global Parameters	91
Setting Global Variables From the Command Line	91
The Main Global Parameters	92
The Format Pop-Up Menu	94
Customizing the Format Pop-Up Menu	96
renderControls	96
guiControls	98
Monitor Controls	101
Colors	102
enhancedNodeView	102
Application Environmental Variables	104
Custom Variable Loading Order	104
Script Environmental Variables	104
Adding Media, Retiming, and Remastering	107
About Image Input	107
Adding Media to a Script	107
Dragging and Dropping Media Into Your Script	108
Image Sequence Numbering	108
Referring to Media Using File Paths	109
Using the FileIn (SFileIn) Node	110
FileIn Source Parameters	111
FileIn Timing Parameters	114
Pulldown and Pullup	116
Reintroducing 3:2 Pulldown After Transforming Media	117
Retiming	117
Fast versus Best Settings for Adaptive Retiming	120
Understanding the Retiming Parameters	123
The TimeX Node	123
Multiple Branches	124
Manual Manipulation of Time	125
Time Notation for a FileIn	125
Remastering Media	126
Fast versus Best In Remastering Parameters	127
Automatic Scene Detection for Multiple Shots	127
Convert Parameters	128
Working With Extremely High-Resolution Images	130
Adjusting the Cache for High-Resolution Images	131
Tuning the Amount of RAM Shake Uses	132
Using Shake With Final Cut Pro	132
How Sent Clips Are Arranged in Shake	133
Unsupported Media and Effects	134
Sending Clips From Final Cut Pro	135
The TimeRange of Scripts Generated From Final Cut Pro	136
Sending Media Back to Final Cut Pro	136
Using Proxies	137
Using Proxies	137
What Are Proxies?	137
Proxies and Final Low-Resolution Output Renders	137
Shake’s Three Proxy Methods	138
Using interactiveScale	139
Using Temporary Proxies	141
Changing the Aspect Ratio to 0.5	143
Customizing P1/P2/P3 for a Script or Session	143
Permanently Customizing Shake’s Proxy Settings	144
Using Pre-Generated Proxy Files Created Outside of Shake	148
Pre-Generating Your Own Proxies	150
Rendering Proxies on the Command Line	153
Pre-Generated Proxy File References in FileIn Nodes	154
Anamorphic Images and Pre-Generated Proxies	155
How Proxy Paths Are Defined	155
Proxies of YUV Files	156
Organizing Proxy Files	156
Full-Resolution Proxies and Network Rendering	157
Customizing the Format of Pre-Generated Proxies	158
Pre-Generating Proxies Outside of the User Interface	160
Using Pre-Generated Proxies in Your Script	161
Keeping High-Resolution Elements Offline	162
When Not to Use Proxies	163
Do Not Use Proxies for Tracking	163
Proxies and Z-Depth	163
Proxy Parameters	164
In the Globals Tab	164
Adding Your Own Entry to the proxySet Pop-Up Menu	165
FileIn	166
Compatible File Formats and Image Resolutions	167
File Formats	167
Shake Does Not Support HDV	167
Image Sequences	167
QuickTime Files	168
Image Formats That Support tTmp Files	168
Nodes That Create tmp Files	170
Table of Supported File Formats	170
Format Descriptions	173
IFF	173
CIN	173
DPX	174
OpenEXR	174
JPEG	177
MOV, AVI	177
PSD (Photoshop)	177
rgb, sgi, bw, raw, sgiraw	177
rla, rpf	177
yuv, qnt, qtl, pal	177
Support for Custom File Header Metadata	178
Table of File Sizes	180
Controlling Image Resolution	180
Combining Images of Differing Resolution	181
Changing Resolution	181
Nodes That Affect Image Resolution	183
Fit	183
Resize	184
Zoom	185
Remastering to a Different Resolution With Proxies	185
For more information on working with proxies and high-resolution images, see Chapter 3, “Adding M...	185
Cropping Functions	186
AddBorders	186
Crop	186
Viewport	187
Window	189
Importing Video and Anamorphic Film	191
The Basics of Processing Interlaced Video	191
Preserving, Eliminating, and Creating Interlacing	191
Understanding Video Interlacing	192
Common Issues When Compositing Interlaced Images	194
Setting Up Your Script to Use Interlaced Images	196
Setting the deInterlacing Parameter of Each FileIn Node	197
How to Determine Field Dominance	198
Setting the reTiming Parameters of Each FileIn Node	198
Displaying Individual Fields in the Viewer	200
Zooming In on Interlaced Images in the Viewer	202
Exporting Field Interlaced Footage	203
JPEGs and Fields	204
Integrating Interlaced and Non-Interlaced Footage	204
Video Functions	205
Interlace	205
DeInterlace	206
Field	207
SwapFields	207
VideoSafe	208
About Aspect Ratios and Nonsquare Pixels	209
What is Anamorphic Video?	209
Anamorphic Examples	210
Properly Viewing Squeezed Images	210
Node Aspect Ratio and the defaultAspect Parameter	211
Compositing Square Pixel Images With Squeezed Images	212
Inheritance of the defaultAspect Parameter for Individual Nodes	213
3D Software Renders	214
Tuning Parameters in Squeezed Space	214
Rendering Squeezed Images	215
Handling Video Elements	215
Preset Formats	216
Table of Common Aspect Ratios	216
Using the Node View	217
About Node-Based Compositing	217
Where Do Nodes Come From?	218
Navigating in the Node View	219
The Node View Overview	219
Favorite Views	220
Using the Enhanced Node View	221
Enhanced Node View Parameters	222
Noodle Display Options	224
Noodle Tension	225
Customizing Noodle Color Coding	225
Customizing Noodle Stippling	225
Creating Custom Stipple Patterns	226
Creating Nodes	226
Selecting and Deselecting Nodes	228
Connecting Nodes Together	231
One Input, Many Outputs	233
Breaking Node Connections	235
Inserting, Replacing, and Deleting Nodes	235
Inserting Nodes Into a Tree	236
Deleting and Disconnecting Nodes From a Tree	238
Copying and Pasting Nodes	239
Moving Nodes	240
Loading a Node Into a Viewer	240
Loading Node Parameters	241
Ignoring Nodes	243
Renaming Nodes	243
Name Nodes Carefully	244
Arranging Nodes	244
Grid Snap	244
Grid Parameters in the Globals Tab	244
Automatic Layout Arrangement	245
Groups and Clusters	246
Clusters	247
Group Parameters	249
Opening Macros	251
Cloning Nodes	251
Thumbnails	253
Customizing Thumbnail Display	253
Adding Thumbnails to Nodes	254
Updating Thumbnails	255
Toggling Thumbnails Between Color and Alpha Channels	256
Defining Which Nodes Are Created With Thumbnails	256
The Node View Shortcut Menu	257
Using the Time View	261
About the Time View	261
Viewing Nodes in the Time View	262
Clip Durations in the Time View	263
Adjusting Image Nodes in the Time View	263
Trimming and Looping QuickTime Clips and Still Images	263
Image Node Controls	264
Image Sequence Timing Controls	264
Customizing How the Last Frame Is Represented	268
Reversing a Clip	269
The Transition Node	270
Customizing the Transition Node	272
Create Your Own Transition Type	273
Using the Audio Panel	277
About Audio in Shake	277
Audio and QuickTime	277
Loading, Refreshing, and Removing Audio Files	278
Previewing and Looping Audio	280
Secondary Peak Meter	281
Muting and Soloing Tracks	282
Playing Audio With Your Footage	282
Viewing Audio	283
Slipping Audio Sync in Your Script	283
Time Shift Subparameters	284
Playback Rate Subparameters	285
Track Gain Subparameters	285
Extracting Curves From Sound Files	285
Create Curves Options	287
Exporting an Audio Mix	288
Mixdown Options	288
Parameter Animation and the Curve Editor	291
Animating Parameters With Keyframes	291
Animating Parameters Using Keyframes	291
Rules for Keyframing	293
Adding Blank and Duplicate Keyframes to Pause Animation	293
Navigating Among Keyframes in the Time Bar	294
Using the Curve Editor	294
Loading and Viewing Curves in the Editor	295
Controlling Curves Displayed in the Curve Editor	296
Navigating the Curve Editor	298
Curve Editor Right-Click Menus	298
The Curve Editor Buttons	299
Splitting the Curve Editor	300
Working With Keyframes	300
Adding Keyframes	300
Selecting Keyframes	302
Deleting Keyframes and Curves	303
Modifying Keyframes	303
Copying and Pasting Keyframes	314
Modifying Curves	315
The Right-Mouse Menu	316
More About Splines	316
The Flipbook, Monitor Previews, and Color Calibration	323
Cached Playback From the Viewer	323
Launching the Flipbook	323
Flipbook Controls	324
Viewing, Zooming, and Panning Controls	325
Memory Requirements	325
Customizing the Flipbook	326
Creating a Disk-Based Flipbook	326
Disk-Based Flipbook Temporary Files	329
Viewing on an External Monitor	330
Customizing External Monitor Output	330
Navigating the Broadcast Monitor	331
Monitor Calibration With Truelight	331
Rendering With the FileOut Node	333
Attaching FileOut Nodes Prior to Rendering	333
The FileOut Node	334
Rendering From the Command Line	336
Using the Render Parameters Window	337
The Render Menu	339
Support for Apple Qmaster	339
Image Caching	343
About Caching in Shake	343
Cache Parameters in the Globals Tab	343
Using the Cache Node	344
When the Cache Becomes Full	345
Caching and Updating Frames	346
Parameters in the Cache Node	347
Commands to Clear the Cache	349
Memory and the Cache in Detail	349
Limits to Shake RAM Usage	350
The Image Cache	350
Preservation of the Disk Cache	351
The Processing Cache	351
Customizing Image Caching Behavior	352
Customizing Shake	355
Setting Preferences and Customizing Shake	355
Creating and Saving .h Preference Files	355
Finding Shake’s Default Settings	356
Creating Your Own Preference Files	356
Possible Preference File Locations	357
Installing Custom Settings and Macros	357
Installing Custom Interface Settings	358
Installing Custom Icons	358
Preference File Load Order	358
Troubleshooting Preference Files	359
Customizing Interface Controls in Shake	359
Color Settings for Various Interface Items	359
Custom Stipple Patterns in the Enhanced Node View	365
Adding Custom Media Formats to the Format Menu	365
Setting Format Defaults	366
Assigning Default Width and Height to a Parameter in a Macro	366
Setting Maximum Viewer Resolution in the Interface	366
Default Timecode Modes and Displays	367
Autosave Settings	367
Undo Level Number	368
Amount of Processors to Assign to the Interface	368
Font Size for Menus and Pop-Up Menus	369
Adding Functions to the Right-Click Menu	369
Adding Functions Into a Menu	370
Opening Scripts With Missing Macros	370
Linking an HTML Help Page to a Custom Node	370
The Curve Editor and Time Bar	370
Customizing File Path and Browser Controls	371
Setting Default Browser Directories	371
Using the UNC File Name Convention	372
Using Relative Path Conventions	372
Adding Personal Favorites to the Browser	372
Assigning a Browser Pop-Up Menu to a Parameter	373
Automatic Launching of the Browser When Creating a Node	374
Automatic Browser File Filters	374
Tool Tabs	375
Setting the Number of Node Columns in a Tool Tab	375
Using the Alternative Icons	375
Attaching a Function to a Button in the Tabs	376
Attaching a Function to a Button Without an Icon	377
Creating Multiple Nodes With One Function	377
Light Hardware Mode	378
Customizing the Node View	378
Using Parameters Controls Within Macros	379
Assigning a Color Control	379
Assigning the Old Color Control	380
Changing Default Values	381
Grouping Parameters in a Subtree	382
Setting Slider Ranges	382
Adding Pop-Up Menus	383
Creating Radio Buttons	384
Creating Push-Button Toggles	384
Creating On/Off Buttons	385
Making a Parameter Non-Animateable	385
Placing a Curve Editor Into a Parameters Tab	386
Viewer Controls	386
Setting Maximum Viewer Resolution in the Interface	386
Onscreen Controls	387
Template Preference Files	392
Changing the Default QuickTime Configuration	392
Environment Variables for Shake	393
Creating the .plist Environment File	395
Using the .tcshrc Environment File	397
Shake Variables	398
To Test Your Environment Variable	399
Using Aliases	399
Interface Devices and Styles	400
Using a Stylus	400
Dual-Head Monitors	400
Customizing the Flipbook	401
Configuring Additional Support for Apple Qmaster	401
RenderQueue Options	401
Part II: Compositing With Shake	403
Image Processing Basics	405
About This Chapter	405
Taking Advantage of the Infinite Workspace	405
Clipped Images	407
Bit Depth	408
Comparing Different Bit Depths	408
Avoiding Color Banding	410
Float	411
Bit Depth Independence	411
The Bytes Node	413
Channels Explained	414
Combining Images With Different Channels	414
Viewing the Number of Image Channels	415
Displaying Individual Channels in the Viewer	415
Changing the Number of Image Channels	416
Compositing Basics and the Alpha Channel	417
Example 1: Compositing Using the Over Node	417
Example 2: Compositing Using the KeyMix Node	418
Example 3; Assigning an Alpha Channel With the SwitchMatte Node	419
Combining Images in Other Ways	420
Using the ClipMode Parameter of Layer Nodes	421
About Premultiplication and Compositing	421
In a Nutshell—the Rules of Premultiplication	422
Problems Caused When Premultiplication Is Ignored	422
The Math of Over and KeyMix	424
Unpremultiplying an Image	426
Remember This	431
Managing Premultiplication	431
Filters and Premultiplication	433
Remember This	433
Nodes That Affect Premultiplication	436
Non-Black Premultiplied Images	436
The Logarithmic Cineon File	437
A Little Further Reading	439
The Hazards of Color Correcting in Logarithmic Color	439
Converting Between Logarithmic and Linear Color	441
Wedging and Color Timing	442
Logarithmic Color and Float Bit Depth	444
Looking at Float Values	448
Float Bit Depth and Third-Party Plug-Ins	449
Compositing With Layer Nodes	451
Layering Node Essentials	451
Don’t Mask Layer Nodes	451
Remember the Rules of Premultiplication	451
Using the clipMode Parameter of Layer Nodes	452
Compositing Math Overview	452
The Layer Nodes	453
AddMix	453
AddText	456
Atop	457
Common	458
Constraint	459
Copy	460
IAdd	461
IDiv	461
IMult	462
Inside	462
Interlace	463
ISub	463
ISubA	463
KeyMix	464
LayerX	465
Max	465
Min	465
Mix	466
MultiLayer	466
Outside	466
Over	466
Screen	467
SwitchMatte	467
Under	468
Xor	468
ZCompose	469
Other Compositing Functions	470
AddShadow	470
DropShadow	470