Loadstar 17/017.d81/game design.3

Text File | 1985-01-01 | 5.8 KB | 345 lines

      ╟AME ─ESIGN FOR THE ├-64
          ┬Y ╥OBERT ┴LONSO

  <CONTINUED FROM PREVIOUS ARTICLE>



┴LIENS, ┴IRPLANES AND ╙YMBOLS

  ╬OW THAT YOU HAVE A COMPLETE CUSTOM

CHARACTER PROGRAM, YOU CAN START TO

DESIGN SOME ALIEN CREATURES,

AIRPLANES, OR ANY OTHER GRAPHIC SYMBOL

YOU MIGHT LIKE TO SEE IN YOUR

PROGRAMS.  ╧NE VERY PRACTICAL

APPLICATION OF CUSTOM CHARACTERS IS

FOR FOREIGN ALPHABETS LIKE THE ╞RENCH

ALPHABET, WHICH USES ACCENT MARKS.

  ├USTOM CHARACTERS ARE GOOD TO HAVE,

BUT SINGLY THEY REALLY DON'T LOOK LIKE

MUCH ON THE SCREEN BECAUSE ├OMMODORE

64 CHARACTERS ARE VERY SMALL.  ╘O

REALLY HAVE A DISTINGUISHABLE DESIGN,

YOU WILL HAVE TO CREATE SEVERAL

CHARACTERS AND PLACE THEM SIDE BY SIDE

OR ONE ON TOP OF THE OTHER.  ╘O

ACCOMPLISH THIS, ALL THAT YOU WILL

HAVE TO DO IS DRAW TWO EIGHT-BY-EIGHT

GRIDS AND LAY THEM OUT SIDE BY SIDE ON

A FLAT SURFACE.

  ╬OW DESIGN YOUR CHARACTERS AND PLACE

BOTH SETS OF DATA STATEMENTS INTO

PROGRAM TWO.  ┴LL YOU HAVE TO DO IS

PLACE THE SECOND SET OF DATA IN A NEW

PROGRAM LINE FOLLOWING LINE 90 AND

CHANGE THE ┘+7 OF LINE 70 TO ┘+15.

╘HE PROGRAM WILL NOW PUT THE FIRST

CHARACTER INTO THE LETTER THAT ┴$ IS

SET EQUAL TO AND THE SECOND CHARACTER

INTO THE LETTER FOLLOWING THAT ONE.

  ╞OR EXAMPLE, IF THE PROGRAM IS ONLY

MODIFIED IN LINE 70 AND THE EXTRA DATA

ADDED INTO A NEW LINE 95, YOU WOULD

END UP WITH THE FIRST CHARACTER DESIGN

WHERE THE LETTER ┴ USED TO BE AND THE

SECOND CHARACTER DESIGN WHERE THE

LETTER ┬ USED TO BE.  ╔F YOU PRESSED

THE LETTERS ┴ AND ┬ ON THE KEYBOARD,

YOU WOULD THEN GET THE ORIGINAL

CHARACTER THAT YOU DESIGNED.  ╘HIS

TECHNIQUE CAN BE EXPANDED TO INCLUDE

NUMEROUS CHARACTERS THAT YOU CAN

╨╥╔╬╘ SIDE BY SIDE AND ONE ON TOP OF

THE OTHER ON A SCREEN TO CREATE

COMPLEX GRAPHIC DISPLAYS.



═ULTI-├OLOR ├HARACTERS

  ├USTOM CHARACTERS CAN ALSO BE

CREATED IN MULTI-COLOR.  ╘HIS MEANS

THAT YOU CAN TAKE A CHARACTER AND

INSTEAD OF JUST SEEING IT IN TWO

COLORS--THE CHARACTER'S COLOR AND THE

BACKGROUND COLOR--YOU CAN SEE IT IN

FOUR COLORS.  ╘HESE COLORS ARE:

CHARACTER COLOR, BACKGROUND COLOR,

BACKGROUND COLOR 1, AND BACKGROUND

COLOR 2.  ╘HESE COLORS ARE CONTROLLED

BY THE REGISTERS AT MEMORY LOCATIONS

53280, 53281, AND 53282.  ╘HE

CHARACTER COLOR IS SET INDIVIDUALLY BY

POKING THE CORRECT VALUE INTO COLOR

╥┴═ AT 55296.

  ╘HE BINARY CODING NECESSARY FOR

CREATING MULTI-COLOR CHARACTERS

GENERALLY FOLLOWS THE SAME THEORY THAT

CREATING ONE-COLOR CUSTOM CHARACTERS

DOES, BUT THERE ARE SOME DIFFERENCES.

╔N A ONE-COLOR CUSTOM CHARACTER, EACH

BIT WHICH IS TURNED ON REPRESENTS THE

CHARACTER'S COLOR, BUT IN A MULTI-

COLOR CUSTOM CHARACTER EVERY TWO BITS

REPRESENT ONE OF THE FOUR POSSIBLE

COLORS.  ┬ECAUSE OF THIS, SOME

HORIZONTAL RESOLUTION IS LOST.  ╙INCE

EACH HORIZONTAL ROW HAS EIGHT BITS,

THAT MEANS THAT THERE ARE ACTUALLY

FOUR TWO-BIT PIXELS, (OR NYBBLES, AS

THEY ARE OFFICIALLY CALLED).  ╔F BOTH

BITS OF A NYBBLE ARE TURNED ON, THEN

THAT NYBBLE BECOMES THE COLOR

SPECIFIED BY COLOR ╥┴═.  ╔F BOTH ARE

OFF, THEN THAT NYBBLE IS COLORED WITH

THE BACKGROUND COLOR SPECIFIED BY

MEMORY LOCATION 53281.  ╘HE OTHER TWO

COLORS ARE PRODUCED BY A ONE-BIT-ON,

ONE-BIT-OFF COMBINATION.  ╘HE

FOLLOWING CHARTS MAY BE HELPFUL TO

YOU.


 ╘┴┬╠┼ 1

 00 ┬ACKGROUND COLOR -╨╧╦┼ 53281,COLOR
 01 ┬ACKGROUND 1     -╨╧╦┼ 53282,COLOR
 10 ┬ACKGROUND 2     -╨╧╦┼ 53283,COLOR
 11 ├OLOR IN ╥┴═



 ╘┴┬╠┼ 2

  0  00 00 00 00     -BACKGROUND COLOR
 85  01 01 01 01     -COLOR AT 53282
170  10 10 10 10     -COLOR AT 53283
255  11 11 11 11     -COLOR ╥┴═
  0  00 00 00 00
 85  01 01 01 01
170  10 10 10 10
255  11 11 11 11


  ╘HE NUMBERS IN ╘┴┬╠┼ 2 WILL PRODUCE

A STRIPED CUSTOM CHARACTER IF THEY ARE

╨╧╦┼D INTO MEMORY USING THE SECOND

EXAMPLE PROGRAM.  ╘O SEE IT IN MULTI-

COLOR MODE, THOUGH, YOU WILL HAVE TO

USE THE FOLLOWING LINE TO ENABLE

MULTI-COLORED CHARACTERS:


    ╨╧╦┼ 53270,╨┼┼╦(53270) ╧╥ 16


┴FTER YOU ARE DONE WITH THE

DEMONSTRATION, YOU CAN DISABLE THE

MULTI-COLOR MODE BY TYPING IN THE

FOLLOWING LINE:


    ╨╧╦┼ 53270, ╨┼┼╦(53270) ┴╬─ 239


  ╘HE NEXT EXAMPLE PROGRAM USES A

DIFFERENT TECHNIQUE FOR LOADING DATA

INTO THE CORRECT ╥┴═ LOCATIONS. ╘HE

DIFFERENCE IS IN HOW IT OBTAINS ITS

VALUE FOR ┴$.  ╔NSTEAD OF HAVING ┴$

ASSIGNED A VALUE AT THE BEGINNING OF

THE PROGRAM, THE VALUE IS OBTAINED

FROM THE DATA STATEMENTS.  ╔F YOU WERE

TO HAVE MANY CHARACTERS THAT YOU

NEEDED CUSTOMIZED, YOU COULD USE THIS

TECHNIQUE EASILY.  ╩UST MAKE THE

SECOND NUMBER OF THE LOOP (╪1) AT LINE

40 THE NUMBER OF CHARACTERS YOU ARE

REDEFINING (CURRENTLY IT IS A 2).  ╘HE

FIRST CHARACTER IN EACH DATA STATEMENT

SHOULD BE THE LETTER THAT YOU WANT

REDEFINED.

  ╘HE THIRD EXAMPLE PROGRAM WILL

PRINT A SMALL SPACESHIP IN THE UPPER-

LEFT CORNER OF THE SCREEN.  ╘HE

SPACESHIP IS COMPOSED OF WHAT USED TO

BE LETTERS ┴ AND ┬ SIDE BY SIDE, THUS

ILLUSTRATING THAT A CUSTOM CHARACTER

CAN BE MORE THAN ONE CHARACTER WIDE.

╘HE SPACESHIP IS IN MULTI-COLOR AND SO

IS THE REST OF THE SCREEN.  ┬ECAUSE

OF THIS, YOU MAY HAVE A VERY DIFFICULT

TIME TRYING TO PLAY AROUND WITH SOME

DIFFERENT ╨╧╦┼S BECAUSE YOU MIGHT NOT

BE ABLE TO READ YOUR SCREEN VERY WELL.

╘HE STRIPES THAT COMPOSE THE SPACESHIP

WILL CHANGE COLORS AS YOU ╨╧╦┼ NEW

VALUES INTO THESE LOCATIONS.

           ------------

  ╔N FUTURE COLUMNS, YOU WILL FIND OUT

WHAT A SPRITE IS AND HOW TO CREATE

ONE.  ┘OU WILL ALSO LEARN HOW TO

DETECT COLLISIONS BETWEEN SPRITES AND

COLLISIONS BETWEEN SPRITES AND YOUR

BACKGROUND.

  ╘HE NEXT INSTALLMENT OF THIS COLUMN

WILL BE DEVOTED TO PROGRAMMING CUSTOM

CHARACTERS IN MACHINE LANGUAGE.


  ╔F YOU WOULD LIKE TO ╥╒╬ THE THIRD

AND LAST EXAMPLE PROGRAM FOR THIS

MONTH, PRESS THE '\' KEY NOW.  ┬ECAUSE
\OAD"GAME PROG-3",8
OF THE NATURE OF THIS PROGRAM, IT DOES

╬╧╘ RETURN TO ╠╧┴─╙╘┴╥.  ┴FTER RUNNING

THIS PROGRAM, PLEASE TURN YOUR

COMPUTER OFF BEFORE RE-ENTERING

╠╧┴─╙╘┴╥.

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