A Versatile Quadruped Limb System with Biped Functionality for
Madagascar3: Europe’s Most Wanted
David Otte
PDI/DreamWorks
Jeff Wang
PDI/DreamWorks
Sven Pohle
PDI/DreamWorks
link locking’. The up-link locking mode keeps the top two of the
three segments in-line, such that it effectively creates a two link
solution. The parallel mode keeps the first and third segments of
the leg parallel to each other while in motion. The lo-link locking
mode is the same as up-link locking, except that instead of the top
two, the bottom two segments are kept in-line.
Figure 1: Marty the zebra as a quadruped, and a biped.
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Introduction
The film Madagascar3: Europe’s Most Wanted required a
quadruped limb system with special functionality that could be not
be achieved with a traditional multi-link ik solver. We needed a system that would support convincing quadrupedal motion, and have
bipedal functionality for when the characters stand up to behave
like humans. Also, to avoid maintaining several systems, it would
need to work for both the front and rear legs on various types of
quadrupedal animals.
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Finding a Solution
We began our development by studying the motion of real
quadruped animals and by having discussions with our animation
department to flesh out what specific features our system would
need. Next, we studied existing in studio quadruped rigs to see
which concepts and features could be referenced for the new system. From this process we concluded that in order to achieve the
functionality and versatility we needed, that the system would need
three modes between which the system could blend. These modes
could be used separately or in combination to handle specific challenges when trying to create great on screen performances.
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The Three Modes
Each of the three modes could be deployed by animators to address
specific animation issues. For example, the anatomy of quadruped
hind legs enforces parallel motion between the first and third leg
segments, which can be achieved using the parallel mode. While
walking or running, quadrupeds will ’lock out’ the last two segments of their front leg. By setting the front leg to lo-link locking, the animator can easily get this behavior. When a quadruped
character stands up and performs as a biped, the animator can turn
the three link front legs into two link arms by blending to lo-link
locking. This transition is seamless, since the beginning and end
positions of the three link chain remain the same while the blend
occurs. Animators use the blending to combine the modes to hit
challenging poses, or simply to get different quality of motion. Uplink locking exists to create a range about the parallel mode with
lo-link locking as the opposite end of that range.
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We based our system on multiple two link ik solvers since we were
unable to produce the up-link and lo-link modes with a traditional
multi-link ik solver.
The system controls the three segments by using a standard two
link solver with it’s goal procedurally offset and rotated about the
foot side axis. This is a very common solution for a quadruped leg
system. However the challenge for this system was finding how
much to rotate the goal about the foot such that the segments would
match the up-link locking, parallel, and lo-link locking solution.
We found that we could run secondary ik systems (one for each
mode) to calculate the angle to place the goal for each of the three
modes. The use of dampening and scaling animation controls made
it necessary to resize the segments procedurally to match the secondary iks systems.
Rigging multiple ik systems individually for each character would
be unrealistic. To address this, we designed the system to only require the position of four joints that describe the location of the
limb segments. Based on these positions, the system procedurally
generates each of the secondary ik systems.
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Figure 2: Up-link locking, parallel, and lo-link locking modes.
The three modes were called ’up-link locking’, ’parallel’, and ’lo-
The System
Results
The quadruped limb system successfully helped animators create
convincing quadrupedal motion, in addition to great bipedal performances. The system proved very versatile, as it is being used on
all the quadruped characters in the film. These characters include
Marty the zebra, Melman the giraffe, Manu the elephant, a circus
horse, and all the circus dogs. Using just one system for all the
quadrupeds kept our character rigs consistent, and easy to maintain.
Future Dreamworks films have adopted and extended the system.