sub routines - changing values

hi. i need to program a pong/breakout game. its virtually all done for me but i need to add a few things.

at the moment i need to change the balls position and make it collide with the walls and paddle. easy enough but im obviously not understanding the use of data registers properly as it doesnt work. im just going to paste in a little but of the code as youll probaly spot how im using it wrong (the variables and constants are declared elsewhere)

CMP.W #play_area_left, ball_row_position
BLE HitLeft

CMP.W #play_area_top, ball_col_position
BLE HitTop

ADD.W #ball_row_displacement, ball_row_position
ADD.W #ball_col_displacement, ball_col_position

BSR RenderBall
RTS

HitLeft
MOVE.W #ball_displacement, ball_row_displacement
RTS
HitTop
Move.W #ball_displacement, ball_col_displacement
RTS

Posted on 2009-01-07 17:58:22 by cool mr croc

Re: sub routines - changing values

CMP.W #play_area_left, ball_row_position
BLE HitLeft

CMP.W #play_area_top, ball_col_position
BLE HitTop

Not sure, but usually 'column' means horizontal position and 'row' means vertical position.

Posted on 2009-01-09 01:06:13 by ti_mo_n

Re: sub routines - changing values

CMP.W #play_area_left, ball_row_position
BLE HitLeft

CMP.W #play_area_top, ball_col_position
BLE HitTop

Not sure, but usually 'column' means horizontal position and 'row' means vertical position.

yeh but the problem is that the program doesnt display the ball, so its how im using values thats the problem i think.

Posted on 2009-01-09 08:12:52 by cool mr croc

Re: sub routines - changing values

Disagree - Columns are vertical yes - so they describe the Horizontal position (the nth column is the nth horizontal position).

Oh, I'd need to see the code that displays the ball to answer that question... however it seems odd to me that you are adding the ball's x and y (column and row) to the ball_col_displacement and ball_row_displacement variables... how are they used in the renderball function? I assume your renderball function prints a character at (row, column) ... may I see it?

Posted on 2009-01-09 08:29:38 by Homer

Re: sub routines - changing values

RenderBall

move.b #1,d1
move.b #93,d0
trap #15 Set pen width
move.l #WHITE,d1
move.b #80,d0
trap #15 Set pen color for ball
move.l #WHITE,d1
move.b #81,d0
trap #15 Set fill color for ball

move.w ball_col_position,d1
move.w ball_row_position,d2
move.w ball_col_position,d3
add.w #ball_dimension,d3
move.w ball_row_position,d4
add.w #ball_dimension,d4
move.b #88,d0 Draw filled circle
trap #15

RTS

Posted on 2009-01-09 08:45:55 by cool mr croc

Re: sub routines - changing values

and yes i got row and column mixed up originally, but my problem is using the sub routine to change values. like i use hitleft to invert the ball_col_displacement but its stopping the program from functioning.

Posted on 2009-01-09 08:49:42 by cool mr croc

Re: sub routines - changing values

this may be easier to look at, its what i have at the moment. the ball moves until it hits the right border then dissapears. im still able to move the bat so the program is still functioning. i look at it in c++ terms, all im trying to do is to run a function that changes the value of a global variable, but i think its my use of data registers which is at fault

*****************************************************
*
* BallMove
*
* Adjust ball position and test ball/bat collision
* or lost ball
*
*****************************************************
BallMove

BSR EraseBall

CMP.W #play_area_right-(ball_displacement/2)-border_width, ball_col_position
BGE HitLeft

MOVE.W ball_col_displacement, d1
MOVE.W ball_row_displacement, d2
ADD.W d2, ball_row_position
ADD.W d1, ball_col_position
BSR RenderBall
RTS
HitLeft
MOVE.W #-ball_displacement, d1
MOVE.W d1, ball_col_displacement
RTS

*****************************************************

Posted on 2009-01-09 09:15:26 by cool mr croc

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