DRAWING DEVICE

• US 20100141649A1
• Filed: 10/09/2009
• Published: 06/10/2010
• Est. Priority Date: 12/09/2008
• Status: Abandoned Application

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: NOTSU, Takahiro
• Application Number:
  US12/576,696
• Publication Number:
  US 20100141649A1
• Time in Patent Office: Days
• US Class Current: 345/419
• CPC Class Codes: G06T 11/40 Filling a planar surface by adding surface attributes, e.g. colour or texture

Abstract

An intersection point is obtained between a triangle forming a 3-dimensional graphics and a straight line. In the straight line, a line in a triangle is obtained. Then, a pixel on the line is obtained, and only these pixels are read from memory for a drawing process. The straight line inside the triangle is determined using an edge functions.

Claims

1. A drawing device which draws an object configured by a triangle on a screen, comprising:

a span generation unit moving a straight line parallel to an X axis or a Y axis of the screen in a direction of the Y axis if the straight line is parallel to the X axis and in a direction of the X axis if the straight line is parallel to the Y axis, and obtaining a line inside the triangle to be drawn; and

a drawing unit drawing pixels on the line.

2. The device according to claim 1, wherein

the span generation unit obtains the line using an edge function f(x, y)=a*x+b*y+c representing an inside of the triangle and defined for each side.

3. The device according to claim 2, wherein:

the span generation unit obtains a range of the line by assuming an X coordinate of a drawable range on a display as CXmin through CXmax, and Y as a Y coordinate of the straight line as follows;

when a>

0,

by an equation X=−

f(0, Y)/a, there is no range when CXmax<

X;

[X, CXmax] when CXmin≦

X≦

CXmax; and

[CXmin, CXmax] when X<

CXmin;

when a₁<

0,

by an equation X=−

f(0, Y)/a, [CXmin, CXmax] when CXmax<

X;

[CXmin, X] when CXmin≦

X≦

CXmax; and

there is no range when X<

CXmin;

when a₁=0,

by an equation X=f(0, Y)/a, [CXmin, CXmax] when X≧

0; and

there is no range when X<

0; and

processes above are performed on three sides of the triangle, and a logical product of obtained ranges is acquired.

4. The device according to claim 1, wherein

the drawing unit draws pixels on a left side and a lower side of the triangle, but does not draw pixels on a right side and an upper side of the triangle.

5. The device according to claim 1, wherein

coordinates of the pixel are integers and coordinates of the straight line in a direction of an axis not in parallel are half-integers.

6. The device according to claim 1, wherein

a determination whether or not the pixels are to be drawn is made on a basis of center coordinates of the pixel.

7. A drawing method for drawing an object configured by a triangle on a screen, comprising:

moving a straight line parallel to an X axis or a Y axis of the screen in a direction of the Y axis if the straight line is parallel to the X axis and in a direction of the X axis if the straight line is parallel to the Y axis, and obtaining a line inside the triangle to be drawn; and

drawing pixels on the line.