Sprite DMA channels can be reused several times within the same display field. Thus, you
are not limited to having only eight sprites on the screen at the same time.
ABOUT THIS CHAPTER
This chapter discusses the following topics:
o Defining the size, shape, color, and screen position of sprites.
o Displaying and moving sprites.
o Combining sprites for more complex images, additional width, or additional colors.
o Reusing a sprite DMA channel multiple times within a display field to create more than
eight sprites on the screen at one time.
FORMING A SPRITE
To form a sprite, you must first define it and then create a formal data structure in
memory. You define a sprite by specifying its characteristics:
o On-screen width of up to 16 pixels.
o Unlimited height.
o Any shape.
o A combination of three colors, plus transparent.
o Any position on the screen.
SCREEN POSITION
A sprite's screen position is defined as a set of X,Y coordinates. Position (0,0), where X =
0 and Y = 0, is the upper left-hand corner of the display. You define a sprite's location by
specifying the coordinates of its upper left-hand pixel. Sprite position is always defined as
though the display modes were low-resolution and non-interlaced. The X,Y coordinate
system and definition of a sprite's position are graphically represented in Figure 4-1.
Notice that because of display overscan, position (0,0) (that is, X = 0, Y = 0) is not
normally in a viewable region of the screen.
- 94 Sprite Hardware -
To Next Page
Loading...
