Graphics Reference
In-Depth Information
footage. They used the LiDAR geometry for several purposes: to help with camera
tracking, to extend the set to cover the whole frame, and to add animated water and
atmospheric elements that realistically interacted with the real-world geometry of
the film set.
For the movie
Zookeeper
, we scanned an entire real zoo in Boston so that
ImageWorks animators could plant the feet of photorealistic digital animals that
interacted with the filmed surroundings. A giraffe might go under and around a
tree because the animators have the model of the real tree in 3D and the data of
the ground that it needs to step on — it interacts with the actors and environment
seamlessly.
Visual effects companies might also use LiDAR data to make a complete textured
digital duplicate of the same set. For example, in
The Matrix Revolutions
, there's
an underground “rave” scene featuring football-field-sized gate mechanisms. They
only built and LiDAR scanned one gate, and used the resulting data as a template
to model and texture all the other gates around the digital set. This required the
processing of the raw LiDAR point cloud into a clean polygonal model that can be
easily manipulated in 3D animation software such as Maya.
RJR: How about laser stripe systems for scanning bodies and props?
Chapman: It's interesting that the concept behind laser stripe scanning was used
in Renaissance times. An artist would make a maquette of a sculpture that was to
be carved from a huge piece of marble. Then they would lower that maquette into
milk or ink in order to study the waterline and analyze how the contour appeared,
before cutting the unforgiving stone. What's happening now is that the waterline is
a laser stripe, and digital cameras and computers take the place of the artist's eyes
and memory. Laser stripe scanners offer instant feedback so that a visual effects
supervisor leaves the set confident that the 3D model is complete and accurate,
and that the animation supervisor will have the expression and muscle movement
reference he or she will need to recreate an actor's performance.
Laser-stripe technology is the oldest and simplest approach, and most of the
equipment we've used for decades has been based on it. The body scanner we use
(Figure
8.9
a) uses four calibrated light stripes and cameras that move down the sides
of a person in unison; it takes about twenty seconds to do a complete pass. This
usually gets about ninety percent of the geometry, but there's always going to be
something occluding the cameras that we must “get hands on” in a software pack-
age like Zbrush and touch up. With any scanning process, there seems to be a point
where you can easily capture a majority of the object or environment in a reason-
able amount of time. Then it becomes a tremendous effort to chase down the rest of
the shape that was hidden from the scanner behind occlusions. It takes some prac-
tice to know when to make the effort to move the scanner to get more viewpoints,
and when the time might be better spent moving on to the next set piece on the long
checklist of things to scan. The scanning service vendor needs to have both the equip-
ment to capture data as well as the talent to process whatever is finally obtained into
something suitable for use by the next person in the production pipeline. This might
mean anything from simple hole filling to recreating a fabric texture and underly-
ing surface curvature to make a seamless model. Since Gentle Giant started out as
