Computer graphics processing and selective visual display system – Computer graphics processing – Animation
Reexamination Certificate
2000-08-10
2004-05-18
Vo, Cliff N (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Animation
Reexamination Certificate
active
06738065
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention most generally relates to computer animation, and more specifically to an animation system that blends motion capture data into a customizable work incorporating motion capture data that produces animation that is much closer to real life movements.
2. Background of the Invention
Animation generally refers to the combination of graphics with the dimension of time. When single images are sequenced together, it gives the appearance of movement. Prior to computers, animators drew hundreds of images to represent a single cartoon movement. Computers now automate the drawing of the images to some extent and aid in manipulating the images to portray certain movements.
Computer animation is well known in the art, and the animator uses the processing power of the computer to create images and motion sequences that represent the desired animation. While it is relatively simple to create jagged and unrealistic movements, generating interactive sequences of animation that follow natural human/animal motion is difficult to create.
To produce quality computer animation, it is necessary to study the motions of the object being represented and form an animation program on the basis of the analysis. Animation that perform the motions of a human require observation by the animator. On the basis of the observations, a program for producing the same motions by the computer model is formed. But, observations are subjective and based on the understanding of the animator. Therefore, the animator's representation always incorporate some deviation from reality.
An animator applies kinematics to the motions, which describes the motions only in terms of positions, rotation, scaling, velocities and accelerations, neglecting the forces and torques responsible. Kinematics analysis only generates a line picture representing parts constituting a human or animal body, and a three-dimensional model of the human or animal body cannot be displayed realistically on a screen.
Keyframing has been used to produce animation that involves identifying the position of body parts and interpolating between the positions of the body parts in successive key frames to generate the intermediate positions of the body parts over the time interval of the animation. Forward kinematic models have generally been discussed in relation to the interpolation techniques. This concept of keyframing builds motion sequences frame by frame and is fairly costly and time consuming. In addition, this method requires expertise to generate quality realistic motions.
Another method of computer animation, motion capture, users sensors attached to a subject which are used to capture data representing the positions of the joints/body parts over time during the performance of a desired motion. The result is a recorded motion sequence for a particular motion. This recorded motion drives a forward kinematic model to produce a desired animation. There are several disadvantages in the prior art associated with motion capture, namely the recorded motion data is sometimes limited by the motions of the recorded subject.
Inverse kinematics (IK) for computer animation has also been used to a limited extent. Inverse kinematics processes a desired position in three-dimensional space and is used to calculate body joint angles. In this approach the particular body part is moved to the desired position resulting from the computer processing. Inverse kinematics often is sometimes used with keyframing to in manipulating the subject into the desired positions with animated character movements.
The IK methodology is based upon complex matrix manipulations that require significant amounts of processing to determine the joint angles associated with limb movements. The amount of processing increases as a cubic of the number of joints involved, translating into lengthy processing times when numerous joints are involved. A human being has more than 200 degrees-of-freedom, which makes it practically impossible to use matrix-based inverse kinematic methods to interactively animate any realistic human or animal-like character in real time. And, matrix-based IK methods may not even work on certain joint configurations known as singular configurations. Furthermore, the prior art notes that with multiple limb and joint movements, the end result of the computations will not appear natural.
In addition, prior IK methods must converge to a solution before the results of the computation can be used for the animation. Partially computed results causes unstable, jerky and oscillatory motion of the limbs, with large positioning errors.
Animation based on keyframing and motion capture is also not highly successful with interactive applications, such as video games and virtual reality simulators. The virtual world of interactive video gives a user total freedom within a three dimensional (3D) space. But, the animator typically employs existing animation and works within the realm most familiar, producing animated characters that all move in like manner.
Besides resulting in poor quality and non-original movement sequences, the existing technology is time consuming and laborious. The frames are created for each movement, and there must be numerous frames with slight movements or the resulting animation appears to move in a jerky fashion. In order to reduce the workload, animators usually limit the number of moving parts. However life-like movement is usually the result of multiple joint and limb movement and using a lesser degree of movement results in an unnatural animation.
An alternative to key-framing and motion capture techniques to create animation is behavioral animation. Behavioral animation refers to movements generated in response to commands and interaction with the environment. This method of animation relies more heavily on computer processing to determine the movement sequence to accomplish the command. High-level goal-based behaviors are typically made possible by using a combination of forward kinematics and inverse kinematics. One advantage of behavioral animation is that the movements can be created on-line and modified in real-time.
Dynamics provides another method of motion analysis. Dynamics analyzes motions of objects based on the relation between movements and forces, as compared to kinematics, which provides motion analysis in terms of positions, velocities and accelerations. Dynamics allows more complex behavioral or animated results. But, computer analysis of motions utilizing dynamics requires data on parameters such as the moments of inertia, the centers of gravity, joint friction and muscle/ligament elasticity of the moving body being represented by the animation. Dynamics motion analysis also requires complex dynamics equations of multiple and simultaneous differential equations.
Solving a problem based on dynamics involves differential equations that describe the relationship between mass and force and torque. There are a number of equations used for describing dynamics, but the most familiar formulations is Lagrange's equation:
∂
L/∂q
i
−d/dt∂L/∂q
i
+&lgr;∂f/∂q
i
+Q
i
=0
where L is the Lagrangian given by kinetic energy (T) minus potential energy (P), q
i
is the ith coordinate, f is a constraint equation, &lgr; is an undetermined multiplier, and Q
i
is the force or torque applied to the ith coordinate.
In general, the prior systems and methods have been unable to provide realistic and like-like motions that are affordable. The complex processing requires very expensive and sophisticated equipment, and time-consuming.
There have been many attempts to alleviate the aforementioned problems and create a natural looking animation that is cost-effective and can be developed quickly and with increased creativity. The invention of PCT/US97/05513 '513 is an animation system involving online computational methods for coordinating limb movements of articulated characters by solving associated forward and inverse k
Maine & Asmus
Vo Cliff N
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