Computer graphics processing and selective visual display system – Computer graphics processing – Animation
Reexamination Certificate
1998-11-18
2003-06-10
Vo, Cliff N. (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Animation
Reexamination Certificate
active
06577315
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a system and method for creating two and three-dimensional computer-assisted animation, and a simple and intuitive user interface for generating a series of animation images from a relatively few source drawings.
BACKGROUND OF THE INVENTION
The field of animation concerns the creation of the illusion of motion by rapidly displaying a sequence of still images, with each image slightly changed from the previous image. In the early years of animation, the drawings were strictly made by hand, which is a tedious and time-consuming process given the large number of drawings required for even a short animation segment. More recently, with the advent of computer graphics technology, computers have been used in the animation process. Animators are often reluctant, however, to depend too heavily on computers for generating drawings because of the noticeable difference between hand drawn figures and objects and computer-generated figures and objects, which appear robotic rather than life-like.
More accepted in the animation field are computer systems permitting animators to create drawings on computer display devices using a mouse, drawing tablet or other input device rather than pen and paper. In these systems, computers are often used to assist an animator in creating an animation sequence by generating intermediate animation frames which are placed in between frames drawn by the animator. The frames drawn by the animator are referred to as key frames or poses. The computer generated intermediate frames are referred to as “in-between” frames and are used to transform an image from one key pose to another. The process of generating these in-between poses is often referred to as “tweening” or “in-betweening.” Generation of the in-between poses is based on computer interpolation between the animator's key frames. The animator specifies the number of in-between frames based on the complexity of the motion, and the computer generates the in-between frames to create a smooth transformation in the resulting animation sequence. The advantage of this technique is that it eliminates the laborious task of manually generating the individual in-between frames. Computer in-betweening for three-dimensional animation is discussed in U.S. Pat. No. 4,600,919 to Stern.
Prior art computer tweening methods are lacking in several respects. First, some prior art tweening systems use simple linear interpolation to generate intermediate poses between key frames. One problem with this approach is that it results in actions in objects that appear “robotic.” The problem can be minimized by increasing the number of key poses, but this requires more manually generated drawings and defeats the purpose of computer-assisted tweening. Another problem is that linear interpolation can cause distortion of objects experiencing rotational motion by shortening segments of the objects at certain angles of rotation. A third problem is that discontinuities in the speed of motion often result if i) the number of in-betweens in adjacent intervals is constant, but the distance between key poses is not, or ii) the distance between adjacent key positions is equal but the number of in-between poses in the interval are not. These problems are discussed more fully in D. H. U. Kochanek, R. Bartels, and K. S. Booth, “A Computer System for Smooth Keyframe Animation,” Rep. No. CS-82-42, University of Waterloo Computer Science Dept., 1982.
Several researchers have developed improvements to the simple linear interpolation technique as discussed in Kochanek et al. One such technique is referred to as the “P-curve.” In this process, the animator traces out a motion path along which an object is to move. In addition, to account for transformations in the object as it moves, the animator can specify a selection function to designate which picture of an object is used for any given frame along the P-curve. For example, the object can be a bouncing ball and the animator can specify that as the ball bounces, a drawing showing a compressed ball can be used.
These prior art techniques are cumbersome for animators to use, however, because they are complicated and do not provide a simple, easy-to-use user interface. There is thus a need for a computer-assisted animation construction system and method that permits an animator to create high quality animation simply and intuitively.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved system and method for computer-assisted generation of animation.
It is a further object of the present invention to provide an improved system and method for computer-assisted generation of animation that creates animated actions more life-like as compared with prior art systems.
It is a further object of the invention to provide an improved system and method for computer-assisted generation of animation such that the animator can simply and intuitively in real-time create a sequence of motion using a plurality of animator-created source poses of an object.
It is a further object of the invention to provide animators with direct artistic control of computer-assisted three-dimensional hand-drawn animation, equal to that which they have when hand-drawing two-dimensional animation in the traditional manner.
The system and method of the present invention improves on the known concept of using a computer to interpolate between sequential key poses of an animation sequence through the use of what are referred to herein as “source poses.” A source pose is an animator-created drawing of an object used in the present invention to create computer-generated poses of the object for animation. Unlike the prior art concept of key poses, a source pose may, but is not required to be, part of the animation.
The invention has application to both two and three-dimensional computer animation. In the system and method of the present invention, any number of source poses can in theory be specified by the animator, but practically 1-7 source poses would be used. These source poses do not necessarily correspond identically to the appearance of the animated object in any of the resulting animated poses. The source poses are used to construct composite poses used in animation sequences, referred to herein as “constructed poses.” In each constructed pose, the object's appearance is constructed from a weighted average of the source poses. A three-dimensional drawing space is provided using a computer-driven stereoscopic viewing system incorporating a computer input device such as a three-axis (6 degree of freedom) position sensor or drawing “wand” which utilizes sensors to track the movement and orientation of the wand in three-dimensional space. The position of the wand is represented by a cursor which is displayed within the three-dimensional drawing space.
A predetermined portion of the three-dimensional drawing space, referred to herein as the “pose transformation space,” is displayed in the viewing system. In one embodiment, the pose transformation space is a tetrahedron. In this case, four source poses are represented by the tetrahedron, one at each vertex. Each point within the tetrahedron represents a constructed pose defined by a unique combination of the four source poses. The drawing wand is moved to control the movement of the wand cursor within the tetrahedron in order to define the transformation of the animated object. The position of the wand cursor relative to each vertex of the tetrahedron controls the constructed pose at that point in time. The constructed poses are composed of weighted averages of the source poses. The constructed poses are viewed in real-time as the wand cursor moves within the pose transformation space enclosed by the tetrahedron, thus providing instantaneous feedback to the animator of the action being created or “scripted.”
In this manner, an animated object can be made to perform any action which, given the nature of the four source poses, can be specified by a progression of three-dimensional graph points determine
Bereskin & Parr
Imax Corporation
Vo Cliff N.
LandOfFree
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