Overview - 3D Postproduction: Stereoscopic Workflows and Techniques - page 21

1.5.2 Core Spatial Condition
In order for a 3D frame to have depth L and R must be slightly different
views of the same scene. Thus, the core spatial condition for 3D is proper
horizontal separation between the L and R images in image pairs. To describe
this horizontal separation, we use the term parallax , a term borrowed from
i elds relating to optics and human visual perception.

In a 3D context, parallax dei nes the amount of horizontal separation between
similar points in L and R. Other commonly used alternate terms for parallax in
a 3D context include: offset, deviation, disparity, and displacement. Typically
parallax is measured as a percentage of total screen width or as a specii ed
numbers of pixels separating similar points on L and R.
There are three possible situations L and R can exist in relation to each other:

• L is to the left of R
• L is to the right of R
• L and R overlap

These three possible situations determine where the subject or area of interest
appears in relation to the viewer and the screen (Figure 1.9 ). Manipulating

LR

AREA OF INTEREST
BEHIND
SCREEN

R

AREA OF INTEREST
AT
SCREEN

RL

AREA OF INTEREST
IN FRONT OF
SCREEN

Figure 1.9 Core 3D Spatial Condition—Position.