http://alienbill.com/vgames/playerpal/
are some javascript tools I wrote that help get
the math right if you want to do more complicated
backgrounds or players...kind of a simple drawing program
> Thank you Dennis and Andrew for your help!
> After the corrections the code runs just fine.
>
>
> Thanks!
>
>
> 11/3/02 9:51:51 PM, "Dennis Debro" <ddebro@xxxxxxxxxxxxx> wrote:
>
> >Hi Rico! Welcome aboard.
> >
> >> I am learning how to draw a playfield. I have read Nick's famous
> >> playfield example and tried different variations that have
> >> been posted on the list. I have written a small program
> >> which only purpose is to draw a rectangle repeatedly
> >> from the top to the bottom of the screen (without worrying about the
> >> reflected portion of the screen). I initialized the playflied
> >> registers to draw something like this:
> >>
> >> * * * * * * * * * * * * * * * *
> >> * *
> >> * *
> >> * *
> >> * *
> >> * *
> >> * *
> >> * * * * * * * * * * * * * * * *
> >
> >Actually your rectangle is more like
> > * * * * * * * * * * * * * * * * * * * *
> > * * *
> > * * *
> > * * *
> > * * *
> > * * *
> > * * *
> > * * * * * * * * * * * * * * * * * * * *
> >
> >Change your $A0 to $80 for PFData2 to get the rectangle you're expecting
> >
> >See my comments below
> >
> >> ; Learning atari playfields
> >> ;
> >> ; Objective: Draw a rectangle many times
> >> ; using the playfield registers.
> >> ;
> >>
> >> processor 6502
> >> include eckvcs.h
> >> org $F000
> >>
> >> START
> >> SEI
> >> CLD
> >> LDX #$FF
> >> TXS
> >> LDA #0
> >>
> >> CLEARMEM
> >> STA 0,X
> >> DEX
> >> BNE CLEARMEM
> >> LDA #$00 ; SET BACKGROUND BLACK
> >> STA COLUBK
> >> LDA #$1E ; SET PLAYFIELD YELLOW
> >> STA COLUPF
> >>
> >> MAINLOOP
> >> LDA #2 ; TURN ON VSYNC
> >> STA VSYNC
> >> STA WSYNC
> >> STA WSYNC
> >> STA WSYNC
> >>
> >> LDA #43
> >> STA TIM64T
> >> LDA #0 ; TURN OFF VSYNC
> >> STA VSYNC
> >>
> >> VBLANKTIME
> >> LDA INTIM
> >> BNE VBLANKTIME
> >
> > STA WSYNC ; end the current scan line
> > STA VBLANK ; end VBLANK period
> >>
> >> LDX #7 ; Use X register to count
> >> ; eight playfield lines
> >> ; to draw.
> >> LDY #191
> >>
> >> SCANLOOP
> >> STA WSYNC ; Accumulator is still 0
> >; STA VBLANK ; remove the VBLANK from your drawing loop
> >>
> >> LDA PFData0,X
> >> STA PF0
> >> LDA PFData1,X
> >> STA PF1
> >> LDA PFData2,X
> >> STA PF2
> >>
> >> DEX ; Decrement X.
> >> BNE SKIPINITX ; If X != 0 then skip next line
> >> LDX #7 ; Repeat playfield drawing
> >> ; by setting X to decimal 7.
> >>
> >> SKIPINITX
> >>
> >> DEY
> >> BNE SCANLOOP
> >>
> >> LDX #30
> > STX WSYNC ; end current scan line
> > STX VBLANK ; Make TIA output invisible (bit 1 is set to 1)
> > STY PF0 ; clear the playfield registers
> > STY PF1
> > STY PF2
> >>
> >> OVERSCAN
> >> STA WSYNC
> >> DEX
> >> BNE OVERSCAN
> >>
> >> JMP MAINLOOP
> >>
> >> org $FF00 ; GRAPHICS DATA STARTS HERE
> >>
> >> ; Playfield graphic is supposed to look like this:
> >> ;
> >> ; * * * * * * * * * * * * * * * *
> >> ; * *
> >> ; * *
> >> ; * *
> >> ; * *
> >> ; * *
> >> ; * *
> >> ; * * * * * * * * * * * * * * * *
> >> ;
> >>
> >> PFData0
> >> .byte $F0,$10,$10,$10,$10,$10,$10,$F0
> >>
> >> PFData1
> >> .byte $FF,$00,$00,$00,$00,$00,$00,$FF
> >>
> >> PFData2
> >> .byte $FF,$A0,$A0,$A0,$A0,$A0,$A0,$FF
> >>
> >>
> >> ORG $FFFC
> >> .WORD START
> >> .WORD START
> >
> >
> >
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> >
> >
>
>
>
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