Practical Algorithms for 3D Computer Graphics, 2nd Edition

4.2. Hidden surface drawing and rasteriz a tio n 97

(x

3

, y

3

, z

3

)

(x

2

, y

2

, z

2

)

(x

1

, y

1

, z

1

)

(X

3

, Y

3

)

Scanline j

Projection plane

(the screen or

framebuffer)

Polygon k

P

(X

1

, Y

1

)

Pixel (i, j)

Y

z

y

x

Viewpoint (0,0,0)

(X

2

, Y

2

)

X

Figure 4.6: Projecting back from the viewpo int through pixel (i, j) leads to a point in

the interior of polygon k. (It is also common, in OpenGL for example, for the view

vector to be aligned with the z axis.)

There are some important details regarding the Z buffer procedure: Following

the convention established in section 2.12.7 the viewpoint V occurs at (0, 0, 0)

and the direction of view is alon g the x axis. It is therefore the x component ...