Computer graphics processing and selective visual display system – Computer graphics processing – Shape generating
Reexamination Certificate
1998-08-10
2001-05-15
Zimmerman, Mark (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Shape generating
Reexamination Certificate
active
06232986
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a three-dimensional graphics processing apparatus which carries out a drawing processing of a polygonal object.
(2) Description of the Related Art
A three-dimensional (3D) graphics processing apparatus which carries out a drawing processing of a polygonal object (hereinafter called a polygon) is known.
In the 3D graphics processing apparatus, polygon data from a CPU is input to a geometric transformation unit. The geometric transformation unit performs various geometric transformations for the input polygon data, such as a modeling transformation, a viewpoint transformation and a perspective projection. As a result of such transformations, the geometric transformation unit supplies polygon data, including vertex data (or vertex coordinates and a vertex color value) of the polygon on a screen coordinate system, to a drawing processor. The drawing processor performs a drawing processing for the polygon data from the geometric transformation unit, and produces a grid of pixel data defining an image of the polygon on a CRT screen as a result of the drawing processing. The pixel data produced by the drawing processor is stored in a frame memory. Hence, the image of the polygon is displayed on the screen of a CRT (cathode ray tube) monitor based on the pixel data stored in the frame memory.
Japanese Laid-Open Patent Application No. 7-325933 discloses a 3D graphics processing device which is designed for speedy drawing processing.
FIG. 21
shows a conceivable drawing processor
99
which is conceived that it performs a drawing processing similar to a drawing processing performed by a drawing processor of the 3D graphics processing device of the above-mentioned publication.
As shown in
FIG. 21
, in the drawing processor
99
, the polygon data from the geometric transformation unit (not shown in
FIG. 21
) is supplied to a vertical parameter computation unit (V/PC)
100
. As described above, the geometric transformation unit produces the polygon data including vertex data (or vertex coordinates and a vertex color value) of a polygon on a screen coordinate system, obtained as a result of the geometric transformations. The vertical parameter computation unit
100
calculates vertical parameters, which are used by a digital differential analyzer (hereinafter called DDA) algorithm with respect to a vertical direction of the polygon, based on the polygon data.
The vertical parameters and the polygon data are supplied to a vertical DDA unit (V/DDA)
101
by the vertical parameter computation unit
100
. The vertical DDA unit
101
performs a vertical DDA processing of the polygon data with respect to the vertical direction of the polygon, based on the vertical parameters from the vertical parameter computation unit
100
. As a result of the vertical DDA processing, the vertical DDA unit
101
produces exterior endpoint data (or endpoint coordinates and an endpoint color value) indicating intersection points between scan lines and the polygon right and left edges.
The exterior endpoint data are supplied to a horizontal parameter computation unit (H/PC)
102
by the vertical DDA unit
101
. The horizontal parameter computation unit
102
calculates horizontal parameters, used by the DDA processing with respect to a horizontal direction of the polygon, based on the exterior endpoint data from the vertical DDA unit
101
.
The horizontal parameters and the polygon data are supplied to a horizontal DDA unit (H/DDA)
103
by the horizontal parameter computation unit
102
. The horizontal DDA unit
103
performs a horizontal DDA processing of the polygon data with respect to the horizontal direction of the polygon, based on the horizontal parameters from the horizontal parameter computation unit
102
. As a result of the horizontal DDA processing, the horizontal DDA unit
103
produces a grid of pixel data defining an image of the polygon on the CRT screen. Specifically, the horizontal DDA unit
103
produces intermediate point data indicating intermediate-point coordinates and an intermediate-point color value for each of intermediate dots between the endpoints on the polygon right edge and on the polygon left edge, based on the horizontal parameters. Then, the pixel data, including the endpoint data produced by the vertical DDA unit
101
and the intermediate point data produced by the horizontal DDA unit
103
, is temporarily stored in a pixel buffer
104
.
After the temporary storing of the pixel data in the pixel buffer
104
is performed, the pixel data is supplied from the drawing processor
99
to the frame memory (not shown in FIG.
21
). Hence, the image of the polygon is displayed on the screen of the CRT monitor (not shown) based on the pixel data stored in the frame memory. The entire operation of the drawing processor of
FIG. 21
is controlled by a control unit (not shown).
FIG. 22
shows an essential part of the conceivable drawing processor
99
of FIG.
21
. In
FIG. 22
, there is shown a configuration of the essential part of the drawing processor
99
which is conceived that it is similar to a configuration of the drawing processor of the 3D graphics processing device of the above-mentioned publication.
As shown in
FIG. 22
, the vertical parameter computation unit (V/PC)
100
includes a storing part
115
having various registers which store the polygon data supplied by the geometric transformation unit (not shown). The polygon data includes vertex data of the polygon on the screen coordinate system obtained as a result of the geometric transformations. Generally, the vertex data for one of vertices of a polygon is constituted by an x-coordinate (SX) on the screen coordinate system, a y-coordinate (SY) on the screen coordinate system, a z-value (SZ) and a color value (CL). The z-value (SZ) represents a typical distance of the vertex from a viewpoint of the polygon. The color value (CL) indicates an intensity of a color of the vertex.
In the configuration of
FIG. 22
, an example of the drawing processing of the polygon in the form of a triangle ABC as shown in
FIG. 23A
is taken into consideration. It is supposed that the vertex data for a vertex A of the triangle ABC is constituted by (SX0, SY0, SZ0, CL0), the vertex data for a vertex B of the triangle ABC is constituted by (SX1, SY1, SZ1, CL1), and the vertex data for a vertex C of the triangle ABC is constituted by (SX2, SY2, SZ2, CL2). In the configuration of
FIG. 22
, the polygon data items (SX0, SY0, SZ0, CL0), (SX1, SY1, SZ1, CL1) and (SX2, SY2, SZ2, CL2) are stored in the registers of the storing part
115
.
The vertical parameter computation unit
100
includes an arithmetic unit
116
which calculates a plurality of differential values based on the polygon data items stored in the storing part
115
. In the drawing processing of
FIG. 23A
, the plurality of differential values are calculated by the arithmetic unit
116
as follows:
dSX0Y =
(SX1-SX0)/(SY1-SY0)
dSX1Y =
(SX2-SX1)/(SY2-SY1)
dSX2Y =
(SX2-SX0)/(SY2-SY0)
dSZ0Y =
(SZ1-SZ0)/(SY1-SY0)
dSZ1Y =
(SZ2-SZ1)/(SY2-SY1)
dSZ2Y =
(SZ2-SZ0)/(SY2-SY0)
dCL0Y =
(CL1-CL0)/(SY1-SY0)
dCL1Y =
(CL2-CL1)/(SY2-SY1)
dCL2Y =
(CL2-CL0)/(SY2-SY0)
(1)
For example, the differential value dSX0Y indicates a gradient of the x-coordinate of the polygon left edge AB with respect to the y-coordinate thereof, as is apparent from the first one of the above formulas (1).
As shown in
FIG. 22
, the vertical parameter computation unit
100
includes a vertical parameter storing part
117
. The differential values dSX0Y, dSX1Y, dSX2Y, dSZ0Y, dSZ1Y, dSZ2Y, dCL0Y, dCL1Y and dCL2Y produced by the arithmetic unit
116
in accordance with the above formulas (1) are stored in registers of the vertical parameter storing part
117
. These differential values are called the vertical parameters.
The vertical DDA unit
101
includes a storing part
120
having various registers which store the polygon data items and the differential values from the vertical
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
Zimmerman Mark
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