This chapter begins with a brief overview of playfield features, including definitions of
some fundamental terms, and continues with the following major topics:
o Forming a single "basic" playfield, which is a playfield the same size as the display
screen. This section includes concepts that are fundamental to forming any playfield.
o Forming a dual-playfield display in which one playfield is superimposed upon another.
This procedure differs from that of forming a basic playfield in some details.
o Forming playfields of various sizes and displaying only part of a larger playfield.
o Moving playfields by scrolling them vertically and horizontally.
o Advanced topics to help you use playfields in special situations.
For information about movable sprite objects, see Chapter 4, "Sprite Hardware." There are
also movable playfield objects, which are subsections of a playfield. To move portions of a
playfield, you use a technique called playfield animation, which is described in Chapter 6,
"Blitter Hardware".
PLAYFIELD FEATURES
The Amiga produces its video displays with raster display techniques. The picture you see
on the screen is made up of a series of horizontal video lines displayed one after the
other. Each horizontal video line is made up of a series of pixels. You create a graphic
display by defining one or more bit-planes in memory and filling them with "1"s and "0"s
The combination of the "1"s and "0"s will determine the colors in your display.
Each line represents one sweep of an electron beam which is "painting" the picture as it
goes along.
________________________________________
| | |
| | --->----->----->----->----->---->--- |
| | ____________________________________ |
| | ____________________________________ |
| | ____________________________________ |
| | __________________ |
| | __________________ |
| | |
| | VIDEO PICTURE |
| | __________________ |
| | __________________ |
| | ____________________________________ |
| | ____________________________________ |
| | _____________________________________ |
| | ____________________________________ |
\ / |________________________________________|
Figure 3-1: How the Video display picture is produced
VIDEO PICTURE
The video beam produces each line by sweeping from left to right. It produces the full
screen by sweeping the beam from the top to the bottom, one line at a time.
- 34 Playfield Hardware –
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