Computer graphics processing and selective visual display system – Computer graphics processing – Animation
Reexamination Certificate
1998-09-30
2001-04-17
Vo, Cliff N. (Department: 2772)
Computer graphics processing and selective visual display system
Computer graphics processing
Animation
C345S441000, C345S426000
Reexamination Certificate
active
06219070
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to rendering graphical images having a three-dimensional appearance on a computer display screen. In particular, the present invention relates to systems and methods for displaying moving polygons on a computer display screen using a technique whereby the values of display parameters to be used with pixels on the display screen are repeatedly interpolated and adjusted to provide the appearance of smooth motion.
2. The Prior State of the Art
As computers have become more powerful and widely used during recent years, one application of computers that has become increasingly valuable is the rendition of objects on computer display screens. Displaying images of objects on computer display screens has been used in computer-aided design and manufacture, computer modeling of objects, the internet, computer games, and many other areas. One particularly valuable technique of displaying objects involves generating an image that is perceived by the human eye as having depth and other three-dimensional features.
A known method for graphically modeling an object in preparation for displaying a three-dimensional image of the object involves approximating the curvature of the object with a series of adjacent polygons whose vertices lay on the object's surface. For example,
FIG. 1
illustrates a simple object that is modeled by arraying a series of polygons on the surface thereof. Object
10
has been divided into a set of triangles (including triangles
12
,
14
,
16
,
17
,
18
, and
19
) in accordance with this technique. The coordinates of the vertices of the triangles and other polygons may be stored in a computer-readable medium so that a computer may display the image of object
10
, with the option of manipulating the coordinates to simulate motion or other dynamic modeling of the object. Prior to being rendered on a flat display, these triangles and other polygons of
FIG. 1
are typically projected into a two-dimensional perspective, since the pixels of computer display screens exist in two dimensions Methods of displaying polygons or other objects on a display screen typically involve the use of computer-executable code that interprets the vertex coordinate information stored in the computer-readable medium or other information defining the object and transforms the information into signals causing appropriate pixels on a display screen to be lighted
Conventional methods of simulating motion of an object, such as object
10
of
FIG. 1
, have limitations that frequently give the object a jumping and non-continuous appearance. The limitations of such methods can be understood in reference to
FIGS. 2
a
-
2
b
and
3
a
-
3
e,
which illustrate an example of displaying motion of a triangle on a computer display screen.
FIG. 2
a
illustrates triangle
100
a
as defined in a coordinate system existing on a computer-readable medium at a selected point in time. The coordinate system has integer values that correspond to pixels on the computer display screen on which triangle
100
a
is to be displayed. At this instant depicted in
FIG. 2
a,
triangle
100
a
has vertex
102
a
at (2.00, 0.25), vertex
104
a
at (4.00, 3.25), and vertex
106
a
at (5.00, 1.75). When triangle
100
a
is modeled in three dimensions, there will also be a z-coordinate value for each vertex, but for purposes of clarity, the z-coordinate values are not identified herein. Moreover, each vertex is associated with one or more pixel display parameters that dictate the display properties of the pixels on the computer display screen when the vertices of triangle
100
a
are depicted thereon. In this example, vertices
102
a,
104
a,
and
106
a
have a generic pixel display parameter of d
1
, d
2
, and d
3
, respectively. Typically, vertices or other points to be displayed on a computer display screen have pixel display parameters of r, g, b (red, green, and blue color parameters), a (transparency or opacity parameter), and u, v, w (texture and depth parameters).
FIG. 2
b
further illustrates triangle
100
a
having been subjected to lateral motion over time. During selected increments of time, triangle
100
a
has been successively transformed in the computer-readable medium to triangles
100
b,
100
c,
and
100
d.
The motion of triangle
100
a
to triangle
100
b
has been generated by incrementing the y-coordinate of each vertex by 0.25. Likewise triangles
100
c
and
100
d
have been defined in the computer-readable medium by incrementing the y-coordinates of the vertices of the preceding triangles by 0.25.
FIGS. 3
a
-
3
e
illustrate a conventional method by which the successive triangles
100
a
-
100
d
of
FIG. 2
b
are displayed on a computer display screen
210
. Because display screen
210
has pixels only at positions that correspond to integer coordinates of the coordinate system of
FIGS. 2
a
and
2
b,
the coordinates of the vertices of triangles
100
a
-
100
d
are rounded to the nearest integer. In this manner, the vertices are “snapped” into the integer pixel positions of
FIGS. 3
a
-
3
e.
In addition, the pixel display parameters d
1
, d
2
, and d
3
, are mapped directly to the pixels to which the associated vertices are snapped.
In
FIG. 3
a,
vertex
102
a
(2.00, 0.25) has been snapped to pixel
202
a
having pixel coordinates of (2, 0). In addition, pixel
202
a
has a display property d
1
that directly corresponds to pixel display parameter d
1
of vertex
102
a.
It is noted that snapping vertex
102
a
to pixel
202
a
sacrifices some resolution, since the precise y-coordinate value 0.25 of vertex
102
a
is rounded to a y-coordinate 0 of pixel
202
a
However, since the pixels exist only at integer coordinates, some loss of static resolution is unavoidable. Pixels
204
a
and
206
a
are also lighted in the same way as pixel
202
a.
In addition, the computer-executable code that enables the display of triangle
100
a
may identify and light the pixels
208
a
that are bounded by line segments connecting pixels
202
a,
204
a,
and
206
a.
In this manner, triangle
100
a
is displayed on display screen
210
, albeit with some loss of resolution.
FIGS. 3
b
-
3
e
further illustrate display screen
210
on which triangles
100
b
-
100
d,
respectively, are rendered. The method for selecting the identity and the display properties of the pixels are the same as that described in reference to
FIG. 3
a.
It is noted that the pixel displays
220
a
-
220
c
of
FIGS. 3
a
-
3
c,
which correspond to triangles
100
a
-
100
c,
are identical. Although the precise coordinates of the vertices of triangles
100
a
-
100
c
have changed over time, the identity and the display properties of the corresponding pixels at the integer positions of display screen
210
are completely unchanged. It is further noted that pixel display
220
d
of
FIG. 3
d,
which corresponds to triangle
100
d,
has undergone significant change when compared to the previous pixel display
220
c
of
FIG. 3
c.
These observations are illustrated in
FIG. 3
e,
which shows a composite of pixel displays
220
a
-
220
d.
As triangles
100
a
-
100
d
undergo relatively smooth motion in the computer-readable medium, the corresponding pixels of pixel displays
220
a
-
220
d
are not adjusted in any way except for undergoing an abrupt, integer pixel jump between display
220
c
of
FIGS. 3
c
and display
220
d
of
FIG. 3
d.
When many such triangles or other polygons are combined to model an object in three dimensions, the resulting jumping motion can be noticeable and distracting to the viewer. However, as illustrated in the foregoing example, the prior art methods of simulating motion of a polygon have no way of minimizing the effects of such jumping motion between integer pixel positions.
In view of the foregoing, there is a need in the art for systems and methods for rendering a moving image of a polygon that reduces the jumpiness that has been experienced according to the prior art techniques. In particular, it would be an advance
Baker Nick
Malamy Adam
Parthasarathy Padma
Paternoster Paul
Sfarti Adrian
Padmanabhan Mano
Vo Cliff N.
WebTV Networks Inc.
Workman & Nydegger & Seeley
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