Commodore 64 Uživatelský manuál stáhnout pdf (Strana 63)

This line POKEs V+16 with the number required to "open up" the right

side of the screen. . .the new X position 24 for sprite 0 now begins 24

pixels to the RIGHT of position 255. To check the right edge of the

screen, change line 60 to:

60 POKE V+16,1:POKE V,65:POKE V+l,75

Some experimentation with the settings in the sprite chart will give you

the settings you need to position and move sprites on the left and right

sides of the screen. The section on "moving sprites" will also increase

your understanding of how sprite positioning works.

SPRITE PRIORITIES

You can actually make different sprites seem to move IN FRONT OF or

BEHINDeach other on the screen. This incredible three dimensional illu-

sion is achieved by the built-in SPRITEPRIORITIESwhich determine which

sprites have priority over the others when 2 or more sprites OVERLAPon

the screen.

The rule is "first come, first served" which means lower-numbered

sprites AUTOMATICALLYhave priority over higher-numbered sprites. For

example, if you display sprite 0 and sprite 1 so they overlap on the

screen, sprite 0 will appear to be IN FRONT OF sprite 1. Actually, sprite

o always supersedes all the other sprites because it's the lowest num-

bered sprite. In comparison, sprite 1 has priority over sprites 2-7; sprite

2 has priority over sprites 3-7, etc. Sprite 7 (the last sprite) has LESS

PRIORITYthan any of the other sprites, and will always appear to be

displayed "BEHIND" any other sprites which overlap its position.

To illustrate how priorities work, change lines 50, 60, and 70 in the

program above to the following:

31Z1

5121

7121

I"'~.":I'IM:I

I .. II' _C:"'-' . ~_r'.'-t'-' C:-. f!"'. '-,IC:'!:':'. ...

P~INT. .V-~3,48.FOR~-o~,T089~.POKE~,~~~.NE0T

FORt1=2048T02042 : POKEM, 13: t.1E:>I,T.

POKEV+21,7

POKEV+39,1:POKEV+40,7:POKEV+41,8

POKEV., 24 : POKEV+ 1 , 5121: pm~E',...+16., (I

POKEV+2.34:POKEV+3,60

POKEV+4,44:PC~EV+5,70

You should see a white sprite on top of a yellow sprite on top of an

orangesprite. Of course, now that you see how priorities work, you can

also MOVE SPRITESand take advantage of these priorities in your ani-

mation.

PROGRAMMING GRAPHICS 161

1 2 ... 58 59 60 61 62 63 64 65 66 67 68 ... 82 83

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