Re: A83: sprite problems

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Re: A83: sprite problems


A suggestion for not being able to quit: make sure you do a "pop de" in
your finish routine.  This is all I can see that could be wrong, but you
didn't send the finish part.  

Hope this helps
Jeremy

On Sat, 16 Sep 2000, Andrew Friedley wrote:

> 
> First I want to say thank you to everyone who has helped me on this list so 
> far.
> 
> I am now trying to write my first game in ASM for the ti-83+ using movax's 
> XOR sprite routines.
> 
> Now I am having a bit of a problem with my game loop section.
> The game loop is currently as follows:
> 
> ; GAME LOOP BEGIN
> startgame:
> B_CALL clrlcdfull
> 
> ld d,47 ;initial ship x
> ld e,50 ; initial ship y
> ld bc,sprship ;ship sprite
> 
> ld a,d ;move d to a for drawing
> push de ;push x y coordinates
> 
> CALL SPRXOR
> B_CALL grbufcpy
> 
> ; GAME LOOP INPUT
> gameinput:
> 
> ;get input
> ld a,0FFh ;reset
> out (1),a
> ld a,0FEh
> out (1),a
> in a,(1) ;input arrow keys
> 
> cp 253 ;left
> jr z,shipleft
> 
> cp 251 ;right
> jr z,shipright
> 
> cp 254 ;up
> jr z,shipup
> 
> cp 247 ;down
> jr z,shipdown
> 
> ld a,0FFh ;input clear key
> out (1),a
> ld a,0FDh
> out(1),a
> in a,(1)
> 
> cp 191 ;clear
> jp z,finish
> 
> ; GAME LOOP LOGIC
> gamelogic:
> jp gameinput
> 
> As far as I can see there are no problems with this code, but I am including 
> it for background.  Notice I pushed the de register at the beginning.  This 
> is to save the ship's x,y coordinates during the input section.  If the 
> input section decides an arrow key has been pressed, the code for that key 
> will pop de, erase the ship, modify the x,y coordinates and redraw the ship. 
>   After that, it pushes de back and continues the game loop.  Below is the 
> code for the left key,  I am only including it because the others are almost 
> identical.
> 
> shipleft:
> pop de;
> ld a,d
> ld bc,sprship
> push de
> 
> CALL SPRXOR
> B_CALL grbufcpy
> 
> pop de
> ld a,d
> dec a;
> ld d,a
> push de
> 
> CALL SPRXOR
> B_CALL grbufcpy
> 
> jp gamelogic
> 
> I know I went a bit overboard with the pushes/pops but I did that to try to 
> figure out what was going wrong.  When I move left/right in the game, the 
> sip will move, but it leaves a trail of jibberish pixels behind it.  I have 
> looked at my code over and over, and don't see why this is happening.  Do I 
> need to clear the screen each loop iteration? If so, how much of a 
> performance decrease will this be?  Also, when I press the clear key to 
> quit, the screen goes blank and the run indicator comes on, and the calc 
> just sits there.  I have to reset in order to get back to TI-OS.  Does 
> anybody know how to fix either of these problems?
> 
> Thanks,
> 
> Andrew Friedley
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