GAMES MASTER TUTORIAL, part 3                      With Dr Andy Wright

I was recently asked by a Games Master
user how to get balls bouncing around
realistically. I set out to write a simple
demo for him, and ran into a few puzzles.
I think the demo might beuseful to other
users, so I reproduce it here.

The actual program is very short - just
one module in Games Master Control
Language. It simply places a few sprites
of types 1 and 2 (different coloured
balls) at randomly-chosenX and Y
positions. They are all placed on
collision plane 4, but any old collision
plane would do. Since they are all on the
same plane, the sprites can hit each
other, rather than pass 'behind' or 'in
front of' each other.

*** MODULE 1 ***

BORDER 7
PAPER 0
CLS
PLACE 1,80,80,4
PLACE 1,30,50,4
PLACE 1,110,90,4
PLACE 2,20,100,4
PLACE 2,55,66,4
PLACE 2,77,33,4
PLACE 2,123,99,4

More interesting is the SPRITE DETAILS
setup for the balls. Thisis given below
for sprite type 2, (called SHOT2). Sprite
type 1 is very similar. To bounce
correctly, the sprite must start with a
reasonable Y (up or down)speed, say,
between -10 and +10. Lower absolute values
give less vigorous bounces. Very low
values give no bouncing at all.

Make sure that BOUNCES and FEELS GRAVITY
are set to YES. MOVEMENT TYPE should be
SIMPLE, for automatic motion. You can try
altering X SPEED. The sprites must be EDGE
LIMITED, or they will notbounce off the
screen edge.

SPRITE 2: SHOT2

   TOTAL FRAMES: 1
          WIDTH: 8
         HEIGHT: 7
  CURRENT FRAME: 1
ANIM. SEQUENCE : 0
    CONDITIONAL: NO
  MOVEMENT TYPE: 1   (SIMPLE)
        X SPEED: -1
  PIXEL X SPEED: NO
        Y SPEED: -6
           PATH: 0
 COLLISION TYPE: 1
        BOUNCES: YES
HALTS ON IMPACT: NO
  FEELS GRAVITY: YES
  NEEDS SUPPORT: NO
   EDGE LIMITED: YES

Some of the overall GAME DETAILS also
matter - if the FORCE OF GRAVITY is
higher, the balls will fall faster. The
MAXIMUM FALLING SPEED mustn't be too low,
or the balls will fall more like
snowflakes. Here are the settings I used:

**** GLOBAL GAME VARIABLES ****

   MINIMUM GAME DELAY: 1
     FORCE OF GRAVITY: 1
MAXIMUM FALLING SPEED: 20
        BORDER COLOUR: 0
         DELAYED WRAP: NO
   EVERY CYCLE MODULE: 0
       ROM INTERRUPTS: NO
 ALLOW EXIT FROM GAME: YES
             TOP EDGE: 191
          BOTTOM EDGE: 0

Good Luck from Andy Wright.