Attributes and Behaviors of Primitives - Essentials of Interactive Computer Graphics - page 151

• Fill style. This attribute defines if the interior of the triangle should be
filled. When switched to wire-frame mode, only the outline edges of the
triangles will be drawn. Wire frame. Draw the out-

lines of the primitives, leaving
the interior unfilled.

7.2 Working with Color

Typically, color is expressed as a (red,green,blue) triplet (or ( r , g , b ) ). We refer to

Normalized number. This
is a floating-point number de-
fined between 0

each of the red, green, and blue as a color channel, or a color component. Each of
the color components is defined either as a normalized floating-point number:

0. For
example, the number 1 . 2 is not
a valid normalized number.

. 0and1 .

0 . 0 ≤ r , g , b ≤ 1 . 0

or as an integer:

0 ≤ r , g , b ≤ 255 .

In either case, the minimum number represents no intensity for the corresponding
component, and the maximum number represents full intensity. For example:

0x00FF0000. This is a hex-
adecimal number where each
digit can be between 0 and F
(15).

Color Floating point Integer Packed unsigned integer

white ( 1 . 0 , 1 . 0 , 1 . 0 ) ( 255 , 255 , 255 ) 0x00FFFFFF

( . , . , . ) ( , , )

red 1 0 0 0 0 0 255 0 0 0x00FF0000

green ( 0 . 0 , 1 . 0 , 0 . 0 ) ( 0 , 255 , 0 ) 0x0000FF00

blue ( 0 . 0 , 0 . 0 , 1 . 0 ) ( 0 , 0 , 255 ) 0x000000FF

black ( 0 . 0 , 0 . 0 , 0 . 0 ) ( 0 , 0 , 0 ) 0x00000000

The maximum intensity of the integer representation is limited to 255 and can
be represented by an unsigned 8-bit integer. A packed unsigned integer packs
the three 8-bit integers into bit positions of a 32-bit unsigned integer. This is a
compact way to represent color. The limited and discrete range of 256 (or 2 8 )
intensity levels of the integer representation reflects the capability of a typical
graphics device. The underlying hardware elements of a typical graphics device
are capable of displaying 256 distinct shades for each of the three colors. For this
reason, these types of graphics displays can display a total of

2 8 2 8 2 8 2 24 × × = ≈ 16 million unique colors.