Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Reexamination Certificate
1997-07-31
2001-02-27
Zimmerman, Mark (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
C345S420000, C345S440000
Reexamination Certificate
active
06195098
ABSTRACT:
COPYRIGHT DISCLAIMER
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to the field of three-dimensional computer graphics, and more particularly to a system and method for manipulating and rendering of selected three-dimensional objects within a scene using a computer.
2. Related Art
The advances in Personal Computer (“PC”) technology have made possible the introduction of relatively inexpensive workstations for word processing, accounting, graphical design and other similar applications which previously required dedicated workstations. The use of PC-Based workstations for visualization of three dimensional objects set in three-dimensional space has traditionally been hindered by the demands placed by existing software on the computers. The complex mathematical operations required for correctly drawing and rendering three-dimensional objects including hidden surface removal, application of texture, lighting, shadows, and animating the three-dimensional objects makes heavy demands on the PCs used for this purpose. Typically, the PC-based systems were designed to defer most of the detailed rendering to after the design was complete. Although this compromise improved the performance of the systems, a graphic designer was not able to view a substantially accurate representation of the final scene while designing the scene.
Computational demands placed on PCs are particularly severe when one or more objects located in a complex scene are being manipulated by the designer. In a conventional system, the entire scene is rendered continually while the objects are being manipulated by the designer. As a result, even if most of the scene is not affected by manipulation of the selected object or objects, the entire scene must be updated to account for the movement of the selected objects and their effects on the scene. The computational demand may exceed the ability of many PCs.
It is therefore desirable to provide a system that will minimize the computational requirements for rendering a scene in which one or more selected objects are being manipulated within the scene.
SUMMARY OF THE INVENTION
One embodiment of the invention includes an interactive rendering system which can minimize computational demand while allowing a designer to manipulate one or more selected objects in a scene. One aspect of the present invention is a system which continuously renders the selected objects while the background scene is not continuously rendered. Because there is no need to render the background scene, most of the computational power can be dedicated to the selected objects. In order to give a designer as realistic a view as possible, the perspective and depth relationship between the selected objects and the scene are maintained. It is found that many designers are satisfied with this arrangement.
The present invention is a system for rendering one or more selected three-dimensional objects of a scene containing a plurality of three-dimensional objects. In one embodiment of the present invention, each object is associated with a modifier stack containing digital information describing the appearance of the object. The selected object(s) can be separated from the rest of the objects in the scene by using a flag. The system comprises a rendering engine for generating two-dimensional pixel data for the modifier stacks of objects. The pixel data includes z values corresponding to a distance between the objects and a predetermined point in space. A first video buffer is coupled to the rendering engine for receiving two dimensional pixel data generated by the rendering engine operating on objects in the scene that are not selected. A second video buffer is coupled to the rendering engine for receiving two dimensional pixel data generated by the rendering engine operating on selected objects. The system then compares the z values of pixels in the first and second video buffers and selects the z value which is closest to the predetermined point. Either the data in the scene video buffer or object video buffer will be displayed depending on whether a selected z value comes from the scene video buffer or object video buffer.
To further explain the present invention, it should be noted that rendering involves transforming three dimensional representation of objects in a scene on a two dimensional screen. Each pixel on the screen represents a point in three-dimensional space which has a depth or “z” dimension representing the distance of that point from an observer. When two points in three dimensional space are mapped to the same pixel by the system, the point with the smaller z value is displayed while the point with the larger z value is obscured and therefore not drawn on the screen. The system of this invention maintains a buffer containing, among other information, the z values of every pixel in the scene. The information is used to correctly display selected objects in the scene in relation to the background and other objects in the scene without rendering the entire scene when one of the objects in the scene is being manipulated by the designer.
When a designer begins manipulating one or more selected objects in the scene, the selected objects are flagged and re-rendered frequently while it is being manipulated by the designer. The z values of the selected objects are stored in a separate buffer. The remainder of the scene (with the select objects removed) is rendered once, and is not changed while the objects are being manipulated and therefore the computation requirements for re-rendering are limited to that which is required to correctly render the selected objects and manipulated by the designer and to correctly display the manipulated object in relation to the background and other objects.
While the object is manipulated within the scene, the z values for the pixels of the manipulated object are compared with the z values of the pixels in the scene and each pixel in the manipulated object or objects is displayed either in front of or behind the scene by comparing the z values of the objects' pixels to those contained in the buffer for the remainder of the scene. The use of the z values eliminates the need for re-rendering any portion of the scene which is not changed by the manipulation of the selected object by the designer and therefore significantly reduces the computational complexity of displaying the scene in rendered form while the designer is manipulating an object within the scene.
When the manipulation of the selected objects is completed and the designer releases the objects, typically by releasing the mouse button, the system integrates the manipulated objects back into the existing background scene without the necessity of re-rendering the entire scene by using the values stored in the z buffer reserved for the selected objects.
It should be noted that the input to the rendering engine does not have to be the modifier stack of an object. The present invention is applicable to other ways to represent three-dimensional objects in a scene. Further, it is not essential to use flags to separate selected objects from the scene, as long as the rendering engine can distinguish the status of the objects so that the selected object(s) and the objects of the scene can be separately rendered and delivered to the two video buffers.
These and other objects, features and advantages of the invention will be apparent from the following description which should be read in light of the accompanying drawings in which the corresponding referenced numerals refer to corresponding parts throughout several views.
REFERENCES:
James D. Foley, et al., Computer Graphics, 1990, section 15.2.3 “Extents and Bounding Volumes”, pp. 660-663,
Berteig Rolf Walter
Brittain Donald Lee
Hudson Thomas Dene
Silva Daniel David
Yost Gary S.
Autodesk, Inc.
Hickman Palermo & Truong & Becker LLP
Stevenson Philip H.
Zimmerman Mark
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