Practical Algorithms for 3D Computer Graphics, 2nd Edition

112 4. Basic visualization

Pixel rows

Pixel columns

j+1

i+1i–1

x

0,0

y

i j–1

j

f

b

f

r

f

t

f

L

Figure 4.14: When a point, P , is projected to the view plane its coordinates, (X, Y ),

will not always be dead center in pixel i, j. Blending the brightness of P into adjacent

pixels i, j + 1 ,i + 1, j and i + 1, j + 1 will help to lessen the effect of the display r a s t er

(or framebuffer) being composed of discrete elements.

The projected point is (X, Y ) ( float data types)

Function f rac(x) returns the fractional part of x *

Each pixel is one unit square

i = X //rounded d own to integer

j = Y

f

l

= 1 − frac(X)

f

r

= frac(X + 1)

f

t

= 1 − frac(Y )

f

b

= frac(Y + 1)

set pixel (i, j)