Computer graphics processing and selective visual display system – Computer graphics processing – Graphic manipulation
Reexamination Certificate
2001-07-09
2003-06-03
Vo, Cliff N. (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Graphic manipulation
Reexamination Certificate
active
06573903
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to computer aided design and drafting systems, and more particularly to interactively determining and displaying geometric relationships between three dimensional objects based on predetermined geometric constraints and position of an input device.
DESCRIPTION OF THE RELATED ART
At the present time, the assembly of three dimensional (3D) objects to realistically depict physical models is based upon the utilization of geometric constraints that roughly correspond to real world physical behavior. Traditional computer-aided drafting (CAD) methods for assembling these types of digital models require that a computer operator indicate where and how 3D objects are to be positioned in digital space. The operator indicates a position and orientation for the 3D graphical objects and the computer subsequently produces the digital representation suggested by operator input. If the resulting representation is not correct, the operator deletes the incorrect graphics from the digital model and attempts to create a new representation that meets the desired criteria.
An operator may press a button on a mouse to provide a “tentative point” to the computer to suggest where an object might be placed in 3D space. Depending upon the type of CAD software used, a second tentative point may be required to fully specify the 3D point of interest. The computer responds by placing a graphic “crosshair” to indicate a precise location nearby the point suggested by the operator. If the point suggested by the operator is close to a key coordinate value from an existing 3D object in the digital design file, the computer places the tentative point at that location and redisplays the graphic object selected in a specified “highlight” color. If the resulting location is desired by the operator, a key is depressed on an input device to accept the tentative point and the specific coordinate values are used one time in an immediately following 3D object input operation. If the coordinate location and associated graphic object determined by the computer is not desired by the operator, the mouse button is pressed again to request a different tentative point.
Some CAD software provides a mode of interaction where the software automatically suggests geometrically interesting points near the cursor for consideration in CAD drafting operations. However, these systems work best in two dimensions where there is little ambiguity regarding the true location of the “interesting point” displayed.
Computer programs exist to create and edit solid models in three dimensions. These solids modeling programs provide interactive tools that allow the merging of individual graphic objects such as a cylinder, block, torus or other objects in order to create a new solid model object definition. Some of these programs offer interactive tools to provide a surface to surface cling mode that constrains the motion of one object's surface to the surface of another. However these programs lack the ability to define a constrained assembly methodology.
Once the user accepts the coordinate location suggested by the computer, a second operation usually follows whereby the 3D object is moved to a correct geometric position, and possibly even rotated about one or more specific coordinate axes to produce the desired orientation. Once again, a tentative point mode of interaction may be used to establish the point of rotation, or else a default coordinate value indicating the origin point of the 3D object may be employed as a rotation point. To specify the exact degree of rotation, another tentative point may be obtained, a specific angle value may be provided by the operator, or else the operator may seek an orientation that is acceptable by moving the mouse, which in turn rotates the 3D object until a satisfactory orientation is obtained. Due to the difficulty of interacting in virtual 3D space with only two dimensional (2D) input devices, such as a mouse or the like, and output devices, such as a video monitor or the like, an operator may have to construct temporary geometric elements to fully constrain placement and orientation. Once the 3D object is in place, the temporary construction geometry is deleted from the 3D model.
To insure that the 3D model has been correctly assembled, the CAD operator desires to visualize the model from different perspective points. In present art, this is accomplished by indicating a point of interest in 3D space using one of the previously described coordinate specification techniques, setting a view distance from the point, specifying the axis of rotation for either the view screen or the virtual world, then either providing an explicit angle value or else interactively changing the viewer's perspective point by moving the mouse or other input device. In general, this method of view manipulation is difficult to master as it requires advance knowledge of how the graphic display system is going to respond to modifications to the underlying mathematical transformation representing 3D space on a 2D video screen.
It is very difficult to create 3D designs using 2D tools, such as a mouse and a computer screen. Consider, for example, the difficulty of placing a 3D chair object at a proper location around a 3D table object. The operator typically uses one perspective, such as a top perspective, to place the chair object to a position that appears to be located adjacent the table object. After placing the chair, however, the operator changes perspective to a side view and discovers that the chair object was placed above the table object and not properly on the floor. The operator must then move the chair object down to the floor. Further, the operator may have to reposition the chair object one or more times to place the chair object at a desired location with respect to the table object. Even if more than one view is provided at a time, the operator is typically constrained to work in one view at a time, and thus must typically manipulate the object in several views before the proper geometric relationship is achieved.
It is an objective of the present invention to more rapidly produce computerized representations of 3D models that conform to predefined specifications for appearance, content and relationships among the graphic objects that are assembled to form the design.
It is a further objective of the present invention to eliminate the duty on the part of the computer operator of providing the correct position and orientation of graphic objects to assemble a valid 3D model of a design or system through a rule-based database to verify the juxtaposition of 3D objects Within the intended context of the design.
It is still a further objective of the present invention that the behavior of the graphics objects be constrained by a set of geometric specifications that are constructed in advance of digital data input operations and are encoded in the definition of the 3D objects.
It is still a further objective of the present invention that the position, orientation and projection of the physical model displayed on the screen can be easily altered through the intelligent manipulation of perspective points, viewing distances and rotations of the view without an operator having to master complex, multiple step commands for view manipulation.
It is still a further objective of the present invention that external procedures for the verification of 3D object relationships can occur during digital data input operations to avert the creation of invalid representations of designs.
SUMMARY OF THE INVENTION
A method and system according to the present invention replaces the multiple step mode of 3D coordinate input with a single step assembly methodology defined for each 3D object to be included in the 3D design. In particular, most positions and orientations for 3D objects are tied to the movement of the input device or cursor. A computer system implemented according to the present invention continuously calculates geometric relationships near the cursor for the operator to ac
Autodesk, Inc.
Cao Huedung X.
Gates & Cooper LLP
Vo Cliff N.
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