Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Reexamination Certificate
1998-11-16
2001-05-22
Vo, Cliff N. (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
C345S419000, C345S440000
Reexamination Certificate
active
06236403
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of modeling based on rounding and inverse-rounding of a 3-dimensional object, and, also, relates to a computer-readable memory medium having programs recorded therein for implementing the method of modeling.
2. Description of the Related Art
As we all know, speed at which computers can manipulate information has been increasing at a significant rate, and an ever greater data-processing power has been applied in many areas of technology. Among these, 3-dimensional CG (computer graphics) has become such a familiar technological area as can be found everywhere as in movies, televisions, games, etc. Recent CG images are created by using smooth curved surfaces, successfully representing such complex figures as human bodies and animal bodies. In video images using such a CG technique, not only a generation of 3-dimensional objects but also free deformation of these 3-dimensional objects is utilized, thereby adequately representing movement of these figures. When such a modeling scheme based on smooth curved surfaces is to be used, it should be insured that flexibly manipulable deformation is possible.
As a scheme to achieve flexibly manipulable deformation, a free-form-deform scheme (FFD) is well known. The FFD refers to a concept for representing global deformation of a shape such as extension, bending, and contortion in the 3-dimensional CG. In the FFD, a control grid is generated by arranging a plurality of control points at grid points to surround a 3-dimensional object, and, then, the generated control grid is deformed to change the shape of an interior parameter space. The deformation of the interior parameter space is mapped to the 3-dimensional object. Various researches have been done on this scheme, and the FFD has been employed in a large number of CG-animation generation systems.
The FFD scheme, however, suffers a limitation in flexibility of deformation control depending on the shapes of 3-dimensional objects. Against this background, other schemes have been presented with an aim of generating a control grid reflecting a shape of a 3-dimensional object so as to enhance the flexibility of deformation control. There are other problems, however, such as difficulties to define a control grid, a high computation cost, etc., which remain to be overcome.
Accordingly, there is a need for a method of modeling which achieves flexible deformation without incurring a high computation cost.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a method of modeling which can satisfy the need described above.
It is another and more specific object to provide a method of modeling which achieves flexible deformation without incurring a high computation cost.
In order to achieve the above objects, the present invention presents a modeling method which defines an object shape directly based on a shape of a control grid, and introduces deformation by use of this control grid. This modeling method employs a process which is reverse to that of the FFD. Further, a scheme which generates free curved surfaces from a polyhedra via rounding deformation is employed in order to define the object shape from the control grid. This scheme can easily define a shape of a 3-dimensional object based on information on the control grid by using a simple algorithm, and does not involve costly calculation of a parameter space deformation.
The modeling method according to the present invention has the following advantages:
1) easy to perform local deformation;
2) easy to predict intuitively a transformed shape;
3) great latitude in the shape of the control grid; and
4) low computation costs.
An attempt to employ a method of generating free curved surfaces from a polyhedra by using rounding deformation for the purpose of shape deformation proves that such application of the method is useful. However, a shape cannot be manipulated until the control grid is generated, and this fact puts a limit to the scope in which the method is applicable. In addition, such problems as inability to directly deform a 3-dimensional object, inability to represent a vertex surrounded by discontinuous surfaces, etc., are present. The present invention makes it possible to automatically generate a control grid with respect to an object of any shape, thereby extending the applicability of the method to cover models of any shapes. Further, concepts such as weights, topological divisions, and reference edges are utilized to permit handling of geometrical shapes which could not be properly defined otherwise.
According to the present invention, a method of modeling a 3-dimensional object includes the steps of performing either a rounding operation generating a 3-dimensional object from a control grid or an inverse rounding operation generating a control grid from a 3-dimensional object depending which one of the control grid and the 3-dimensional object is newly provided, the control grid including edges and vertexes and the 3-dimensional object including boundary curves and curved surfaces, deforming the control grid by shifting the vertexes, performing the rounding operation when the control grid is deformed so as to introduce the deformation of the control grid to the 3-dimensional object, attaching a weight to one of the vertexes of the control grid to deform a corresponding one of the curved surfaces of the 3-dimensional object, attaching a weight to one of the edges of the control grid to deform a corresponding one of the boundary curves of the 3-dimensional object, and attaching information on the respective weight to a corresponding one of the vertexes and the edges as an attribute thereof.
According to one aspect of the present invention, the method described above is such that the step of attaching a weight to one of the vertexes results in a topological division of the corresponding one of the curved surfaces.
According to another aspect of the present invention, the method as described above is such that the step of performing the rounding operation refers to the respective attribute attached to the corresponding one of the vertexes and the edges when introducing the deformation of the control grid to the 3-dimensional object.
In the methods described above, attributes are attached to the control grid in relation to the rounding operation, thereby achieving more enhanced representation of shapes in the rounding operation and providing better matches between the rounding operation and an inverse-rounding operation. This allows handling of models in a generic manner.
According to another aspect of the present invention, the method as described above is such that the inverse-rounding operation comprises the steps of defining a vertex with respect to each loop of the 3-dimensional object, said each loop made up from the boundary curves, attaching the attribute to the vertex, and connecting the vertex of a given loop with the vertex of an adjacent loop to generate a straight-line edge therebetween.
In the method described above, a control grid can be generated from a 3-dimensional object of any shape. Also, data of the 3-dimensional object comprised of complex curved surfaces is converted and compressed into data of an object comprised of straight-line edges, thereby reducing the data-processing load.
According to another aspect of the present invention, the method as described above is such that the inverse-rounding operation comprises the steps of removing edges connected to a vertex of a loop when the loop corresponds to a curved surface having the topological division, and generating the control grid after the removal of the edges connected to the vertex.
In the method described above, since the control grid is generated after removing edges connected to the vertex of the loop having the topological division, reversibility is retained even when another rounding operation is performed.
According to another aspect of the present invention, the method as described above is such that the invers
Chaki Youichiro
Chiyokura Hiroaki
Nakamura Atsushi
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
Vo Cliff N.
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