Graphics Reference
In-Depth Information
CHAPTER 5
The DEPTH Workl ow
“There is something that 3D gives to the picture that takes you into
another land and you stay there and it's a good place to be.”
—Martin Scorsese
5.1 Overview
The depth workl ow, along with the geometry workl ow, is exclusive to
3D postproduction ( Figure 5.1) . In the depth workl ow, teams adjust parallax
(horizontal separation) to show viewers where to look in Z-Space. Some depth
decisions are made to insure story continuity, others to insure viewer comfort.
Depth is the workl ow that relates most closely to why the show is in 3D.
In the depth workl ow, teams manipulate parallax to change the apparent
location in Z-Space of the area of interest in a 3D frame. As we learned in
Chapter 1, horizontal parallax represents the distance between similar points
in an image pair as a percentage of screen width (e.g., 3%) and/or a s a n
absolute pixel value (e.g., 20 pixels). As you might expect, horizontal parallax
can remain i xed or vary over the course of a shot.
Depth and editorial are often combined into a single workl ow. The editorial
workl ow provides a visual structure for the show in the realms of timing
and framing. The depth workl ow creates a corresponding visual structure
in Z-Space. In a real sense, then, depth grading is “editing in Z-space.” Like
an editorial cut, a depth cut generates a metadata representation (a decision
list) rel ecting creative depth decisions. Depth, like editorial, is a process
of continuous rei nement. It is not unusual for shots to take multiple trips
through the depth workl ow.
The most important thing to know about depth is that until you have corrected
geometry in a shot (or know that the geometry issue can be resolved), it
wastes resources to depth grade that shot. Why? The short answer is that
 
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