Graphics Reference
In-Depth Information
RJR: When you need to track natural features in plates, what detection and description
strategies do you use?
Roble: When we do automatic feature detection and tracking we tend to use things
like Harris corners. These are important first steps for matchmoving algorithms.
However, we're often trying to specifically followa point an artist has selected in an
image. For example, the artist may know that a CGI character is going to be dancing
on top of a cabinet in the scene. The rest of the points in the scene don't matter; it's
(a)
(b)
Figure 4.23.
(a) In blue- or green-screen environments, artificial features are often introduced
to aid camera tracking, such as the red tape marks in this frame from
Thor
. (b) In natural envi-
ronments, automatically extracted image features such as Harris corners play the same role, as
in this sequence from
Transformers: Revenge of the Fallen
. Scale and rotation invariance may be
necessary to compensate for camera rotation and zoom.
Thor
images appear courtesy of Marvel
Studios, TM & ©2011 Marvel and Subs.
www.marvel.com
.
Transformers: Revenge of the Fallen
©2009 DW Studios L.L.C. and Paramount Pictures Corporation. All Rights Reserved.
