The GEOMETRY Workflow - 3D Postproduction: Stereoscopic Workflows and Techniques - page 109

If you are lucky you may be able to do a global i x that will resolve an
issue. Several tools bundled with editorial systems can “automatically”
correct some geometry issues to some degree. No tool can i x all geometry
issues. Issues can sometimes combine into impenetrable knots and can
become extremely challenging (and resource-intensive) to troubleshoot
and resolve.
The biggest challenge is resolving geometry errors that change over time. For
example, a shot can have an issue at its start, an additional issue starting
Frame 10, and completely new issue starting Frame 60. Each new issue occurs
may require a new or different technique to resolve. For errors that change in
severity over time and that cannot be corrected to automated tools, the choice
is to solve the error through a series of keyframes. One of the biggest issues
is making sure that you do not introduce new issues in the effort to resolve
other issues.
The most important technique in geometry is troubleshooting. And not
troubleshooting only for the source of the issue, but also troubleshooting
for the most resource-effective way to implement a solution. Remember,
it is helpful though not necessary to know what caused the issue in order
to correct it. Teams may choose to address some issues and not others.
Sometimes a single solution will resolve multiple issues.
We can distinguish between two major types of geometry issues: spatial and
temporal. In some cases issues can masquerade as spatial but can actually
be temporal. For example, a scenario in which L and R do not have the
same image magnii cation may be a relatively simple matter of aligning the
proper L with the proper R. When L/R alignment is i xed, magnii cations
then match. In another show, L and R magnii cation may vary over the
course of a shot.
Common spatial geometry issues include:
• Vertical Alignment Mismatch
• Keystoning
• Zoom Mismatch
• Rotation Mismatch
• Iris (depth of Field) Mismatch
• Focus Mismatch
• Lens Distortion Mismatch
• Mirror Warp