Aligning left- and right-eye views and adjusting depth

It is very important that stereoscopic 3D video have differences between the views only in horizontal displacement. Any vertical or rotational misalignment will detract from the viewing experience and may even cause viewer discomfort. Also, it is important to limit the amount and direction of horizontal offset to create comfortable depth.

For example, when shooting with parallel-axis cameras, all of the action is usually in front of the screen, and you need to use horizontal image translation to push most of it behind the screen.

Use the 3D glasses in combination with viewing the output without the glasses to create good alignment and depth settings. You usually want all of the action behind the screen plane, only crossing the screen plane for dramatic or special effect. However, make sure never to create divergence, where the left-eye picture would appear more than 2.5 inches to the left of the right-eye picture on the largest screen where your movie will be shown.

For example, if the largest screen to be used is 16:9 with a 106-inch diagonal, the width is 87% of the diagonal, or about 92 inches. With 1920x1080 content, 2.5 inches is only 52 pixels, so make sure your distant objects are never more than 52 pixels apart.

Stereoscopic 3D Adjust

You can use the Stereoscopic 3D Adjust plug-in to adjust horizontal offset, vertical offset, keystoning, and rotation. This plug-in can be applied at the media level, event level, track level, or video output. For more information, see Adding video effects

You can use the plug-in's controls as follows:

Item	Description
Horizontal Offset	Drag the slider to adjust the horizontal alignment of the left- and right-eye views to set the perceived position of the video relative to screen depth.
Vertical Offset	If left- and right-eye views are not aligned vertically, drag the slider to correct the offset.
Zoom	If left- and right-eye views are not zoomed identically, drag the slider to correct the offset.
Keystone	Drag the slider to correct for image keystoning. Image keystoning occurs when the left- and right-eye cameras are not parallel.
Rotation	Drag the slider to correct for camera tilt in the left- and right-eye views.
Auto Correct	Click to analyze left- and right-eye views and automatically calculate values for Vertical Offset, Zoom, Keystone, and Rotation.
Flip Horizontal	Choose a setting from the drop-down list to flip the image for inverted cameras.
Flip Vertical	Choose a setting from the drop-down list to flip the image for mirror rigs or inverted cameras.
Automatic Crop	Select this checkbox if you want to automatically crop the left- and right-eye views during adjustment to prevent black borders created by the plug-in's adjustments.
Crop	When the Automatic Crop checkbox is cleared, you can drag this slider to adjust image cropping.
Floating windows	Drag the Left or Right sliders as needed to correct for screen-edge violations. If your stereoscopic 3D project contains objects that cross the screen edge and appear in front of the screen, users will see conflicting depth cues: the 3D effect tells the user's eyes that an object should appear in front of the screen, but the edge of the screen contradicts the screen depth. For example, in the following example, dragging the Left slider masks the left edge of the frame to prevent the kayak from crossing the edge of the screen.

TIP

3D depth adjustment is a complex process and is out of the scope of this document. For more information, please review a reference such as 3D Movie Making: Stereoscopic Digital Cinema from Script to Screen by Bernard Mendiburu.
When you're working with a stereoscopic 3D project, a separate checkbox is displayed in the Video FX window for the left- and right-eye video: . By limiting an effect to the left or right eye only, you can use multiple instances of a plug-in with different settings for each eye.