Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Reexamination Certificate
2000-03-03
2003-07-29
Nguyen, Phu K. (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
Reexamination Certificate
active
06600485
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for generating polygons, based on a NURBS (non-uniform rational B-spline) model that is modeled on NURBS surfaces that represent parametric surfaces, and to an image display apparatus wherein that method is employed.
2. Description of the Related Art
FIG. 85
is a diagram that describes a general configuration example of a game apparatus that is a conventional image display apparatus wherein polygons are used. Under the control of a host processor
100
, multiple polygons that configure an object displayed on a display device
400
are input to a geometry computation unit
200
in correspondence with the advance of a game program.
Polygon data input to the geometry computation unit
200
define polygons in three-dimensional local coordinates each having origin coordinates. The geometry computation unit
200
converts the polygon data defined on the local coordinates to a common world coordinate system for all objects.
Also, the polygon data is converted to three-dimensional viewing-point coordinates, which have the view point placed in this world coordinate system as the origin. The viewing point changes as the game program advances, wherefore the polygon viewing-point coordinates are updated in correspondence with these viewing-point changes.
Next, with the viewing point coordinates as the origin, the object is projected onto a screen corresponding to the screen of the display device
400
on which it is displayed, that is, the polygon data are converted to two-dimensional plane coordinates.
The polygon data converted to two-dimensional plane coordinates are next input to a renderer
300
. The renderer
300
, based on the polygon data, performs rendering processes such as adding texturing, lighting effects, and RGB color data.
Then the renderer
300
writes the output of its rendering processing to a video RAM, this is repeatedly read out and sent to the display device
400
, whereby the object can be displayed.
In recent years, however, technology is being adopted that defines humans and other objects displayed in game apparatuses and the like by NURBS models modeled on NURBS (non-uniform rational B-spline) surfaces representing parametric surfaces generated by three-dimensional computer graphics (CG) modeling tools. These NURBS models constitute a technology well suited to defining objects having curved surfaces.
In other words, when an object is shaped with curved surfaces, the object data volume can be made less by defining the object with a NURBS model than by defining it by a set of polygons.
When technology that defines an object with a NURBS model, such as that described in the foregoing, is assumed, the NURBS model cannot be directly handled by a conventional game apparatus. Firstly, therefore, in the game development apparatus, NURBS models are converted to polygons by CG modeling tools, and these polygon data are stored in the memory of the game device.
At this time, the NURBS surface object will be converted into numerous polygons, so the data volume after conversion to polygons becomes very large. For this reason, a large-capacity memory is required to store those data.
It is possible here to reduce the number of polygons configuring one object, depending on the size of the object that is displayed on the screen. For example, the greater the distance becomes from the coordinate position of the viewing point, the smaller becomes the size of the object displayed on the screen, and the fewer may be the polygons that configure the object.
However, with technology which uses objects wherein NURBS surfaces have been divided into polygons beforehand in a game device such as that supposed above, the number of polygons configuring a displayed object is not changed, irrespective of the size thereof. For that reason, the same number of polygons must be processed for each object, irrespective of the display size thereof, and, even if one polygon is smaller than 1 pixel, polygon processing becomes necessary.
Furthermore, it is possible to subject NURBS surface objects to geometry computation processing, not at the polygon vertex data stage but at the NURBS surface control point stage. However, with game devices wherein NURBS surface objects are used, such as is supposed above, geometry computation processing is performed at the polygon vertex data stage, wherefore the processing load becomes heavy.
Furthermore, when NURBS surface objects are deformed, it is necessary for a large volume of polygon vertices to be controlled by the host processor, and for a large volume of polygon data to be transferred over a bus connecting the host processor and the geometry computation unit, wherefore a very high bus band is required.
Also, the more complex a NURBS model surface shape is, the greater increase there is in the volume of computations necessary to find one point (that is, one [set of] vertex coordinates for a polygon) on the NURBS model.
That being so, the more complex the surface shape of a NURBS model is, the more voluminous becomes the processing for converting from NURBS models to polygons, whereupon there arises a danger that the real-time processing ability required by the game apparatus may be impaired.
Now, even in cases where the NURBS model has a complex surface shape, as was mentioned earlier, if that model is positioned a far distance from the viewing point, and the size of the object displayed on the screen is small, that complex surface shape cannot be visually discerned by the player.
Accordingly, when the size of an object on the screen is small, there is no need to faithfully reproduce the shape thereof using a large quantity of polygons, and there will be no problem in simplifying to some degree the surface shape of the NURBS model. If the surface shape of a NURBS model is simplified, the number of polygons converted can be reduced, making it possible also to reduce the polygon data volume. The volume of computations for finding points on the NURBS model will also be diminished, wherefore the conversion process can be speeded up. Alternatively, instead of simplifying the curved surface shape of the NURBS model, it is possible merely to reduce the number of surface sampling points.
However, with a method for converting NURBS models to polygons (i.e. dividing a model into a plurality of polygons) and generating polygons in the game development apparatus supposed in the foregoing, the NURBS models are not simplified, no matter the size of the objects displayed, and, even when the size of a NURBS model of complex shape is small, the points on the NURBS model are computed, and division is made into polygons, for that surface shape as is.
For that reason, conventional game devices (image display devices) require high-capacity memories for storing very large volumes of polygon data, and the polygon data computation means (CPU, etc.) are subjected to heavy loads.
SUMMARY OF THE INVENTION
An object of the present invention, accordingly, is to provide an efficient polygon generation method in technology for converting NURBS surface objects to polygons, and an image display apparatus that uses that method.
Another object of the present invention is to provide a polygon generation method, in technology for converting NURBS surface objects to polygons, wherewith it is possible to reduce the memory capacity for storing post-conversion polygons, together with an image display apparatus that uses that method.
Yet another object of the present invention is to provide a polygon generation method, in technology for converting NURBS surface objects to polygons, wherewith it is possible to reduce the volume of polygon data and other data transferred between a polygon drawing processor (rendering processor) and a host processor, together with an image display apparatus that uses that method.
Still another object of the present invention is to provide a polygon generation method, in technology for converting NURBS surface objects to polygons, wherewith, by directly processing NUR
Furuhashi Shinichi
Nakamura Naoki
Nakane Toshihiro
Yoshida Jiro
Dickstein , Shapiro, Morin & Oshinsky, LLP
Nguyen Phu K.
Sega Enterprises Ltd.
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