Ball Object has holes in it

[Primordial Ooze]

I have started writing my remake of pong tentitivly called 6502Pong. I managed to get the player paddles to show onscreen, but for some reason the ball is drawn, it seems to have holes in them. I double checked my assembly code and everything seems to be in order. Any help would be greatly appreciated.

 

Sincerely,

 

6502Pong

6502Pong.zip

[Wickeycolumbus]

I found the problem and fixed it for you

 

	ldx #0		;get X ready to disable Ball object
							  ;changed from lda to ldx



;	sta ENABL		; removed this line

			; if the visibleballline is non zero,

lda visibleballline	; if the visibleballline is zero
beq FinishBall		; don't draw the ball

lda #2			; otherwise set the accumulator to 2		
sta ENABL		; and draw the ball
dec visibleballline	; and decrement the visibleballline by 1
.byte $2c	;skip over next two bytes. Added this line

FinishBall
stx ENABL	;this 2 byte instruction is skipped if 
		;ball is still drawing.  changed from sta to stx

6502Pong.zip

[Nukey Shay]

It can be simplified further, since the FinishBall tag is only branched to when visibleballline is zero (and subsequently, not drawing the ball). There is a 6-cycle difference between the two cases tho...but that doesn't matter here.

 

SkipActivateBall

lda visibleballline	; if the visibleballline is zero

beq FinishBall		; don't draw the ball

lda #2			; otherwise set the accumulator to 2		

dec visibleballline	; and decrement the visibleballline by 1

FinishBall
sta ENABL		; enable/disable the ball
			; if the visibleballline is non zero,
			; we're drawing it

[Nukey Shay]

BTW is there a reason for using 8-bit sprite GFX for the players? You could make a shorter kernel by using the missiles instead (and resetting the stack pointer to the missiles and ball to enable/disable them).