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674 Chapter 20: Managing Scenes and Projects
General N otes on Extended Attributes and
Channels
Please note the following:
• You can view the extended information via the
File Info button on the input dialog.
• A default File Tag string is provided when you
add an attribute/channel. You can change the
file tag by highlig hting the entry in the list and
then editing the File Tag field immediately
below the list. You can also enable and disable
the attribute/channel with the check box to the
leftoftheFileTagfield.
Note: Each sav ed a ttribute or channel must
haveauniquefiletag. Ifyouspecifymultiple
instances of a file tag, only the first attribute or
channel with that file tag is used.
• AllthecurrentattributesareStringtype
attributes that are stored in the header for
the file, and can be read in plain text via the
exrheader.exe utility (available from the official
Website >Downloadspage).
• Attributes and channels are stored in the file
in alphabetical order according to the ASCII
file tag.
• While this plug-in can write most of the
3ds Max
G-Buffer (page 3–1040) channels,
there is no software that can utilize them yet.
• Attributes and channels are identified by
plain-text (ASCII) st rings. There can be
only one instance of a string tag in any file.
Attributes are data that is stored per frame,
not per pixel, and they are embedded in the
file’s header. Channels are data that is stored
per pixel. In order to maximize flexibility with
other software, this plug-in lets you edit the file
tags. You should only do this if you know the
tag required by s ome other software; other wise
it is best to leave the file tags at their default
values.
• Channels that create multiple “slices” in the
EXR file require multiple file tags. In this c ase,
thefiletagintheuserinterfacecomprises
several sub-tags denoted by square brackets.
For example, t he Normal channel generates
three slices in the EXR file: one for the Normal
vector x data, 1 for y, and 1 for z. In this
instance, the tag string in the user in terface
would read [NX][NY][NZ], and generate slices
w ith the file tags "NX", "NY", and "NZ". T he
filetagisusedbysoftwarethatisreadingthe
EXRfiletoidentifytheintendeduseofthe
channel data. Even standard image channels
are encoded this way, with the tags "R", "G",
"B", and "A " used to denote red, g reen, blue,
and alpha channels respectively.
Extended Attributes
Co mment—A general-purpose comment string
defined by the user. To define the comment,
highlighttheCommententryinthelistandthen
edit the Comments field immediately below the
list.
Computer Na me—Thenameofthecomputerthe
image was saved f rom. In the case of standard
render output during a net render, this is the
machine that rendered the frame.
System T ime—TheUTC(GMT)systemtimeand
datewhenthefilewaswritten.
Local T i me —Thelocaltimeanddate(correctedfor
thetimezone)whenthefilewaswritten.