; *********************›; *   STARS 3D DEMO   *›; * BY CRAIG PATCHETT *›; * ACTION! VERSION   *›; *  BY DON GLOVER    *›; *********************›; system equates›CARD sdmctl=$022F,›     nmien=$D40E,›     random=$D20A,›     wsync=$D40A,›     sdlstl=$0230,›     vdslst=$0200,›     colpf0=$d016,›     color4=$02C8,›     xitvbl=$E462›BYTE index ;used to index into strcol›CARD indrct=$D6 ;pointer for indirect addressing›BYTE ARRAY timer=[8 8 6 6 5 5 3 3 2 2 1 1], ; timers for scrolling›timary=[8 8 6 6 5 5 3 3 2 2 1 1], ;values to reset timers›mancol=[$22 $24 $26 $28 $2A $2C $2E $22], ; star colors›; ***careful-requires a 40k machine to work›dlist(600)=35840, ;display list›strlin(768)=36864, ;star(screen) memory›; *****************************************›strtpl(16), ;addresses of beginning of›strtph(16), ;each star line›strpos(16), ;position of star on line›strcol(192)    ;color of each line›CARD ARRAY strtp(16) ;temp. hold addresses to be›                    ;transferred into strtpl,strtph›PROC setvbv=$E45C(BYTE command,vblankhigh,vblanklow)›; ***********************************›PROC SCROLL(BYTE dummy,starindex) ; star scroll routine›; ACTION! is too much trouble to use here with all the bit twiddling›[›$BD $FFFF ;LDA STRTPL,X›$85 INDRCT ; STA INDRCT›$BD $FFFF ;LDA STRTPH,X›$85 INDRCT+1 ;STA INDRCT+1›$BC $FFFF ; LDY STRPOS,X›$B1 INDRCT ; LDA (INDRCT),Y›$0A         ;ASL›$0A         ;ASL›$91 INDRCT  ;STA (INDRCT),Y›$90 $0F     ; BCC SCRBR1›$A9 $01     ; LDA #1›$88         ; DEY›$C0 $FF     ; CPY =255›$D0 $02     ; BNE SCRBR2›$A0 $2F     ; LDY #47›; SCRBR2›$91 INDRCT  ; STA (INDRCT),Y›$98         ; TYA›$9D $FFFF   ; STA STRPOS,X›; SCRBR1›]›RETURN›; ************************************›PROC cntdwn() ; timer routine›   BYTE starcounter›   scroll(0,13) scroll(0,13) ; move fastest star›   scroll(0,12) scroll(0,12) ; and its twin›   ; now do rest of stars›   FOR starcounter=0 to 11›   DO›      timer(starcounter)==-1›      IF timer(starcounter)=0 THEN›         scroll(0,starcounter) ; scroll if ready›         timer(starcounter)=timary(starcounter) ; reset timer›      FI›   OD›RETURN›; **********************************›PROC vblank() ; vblank routine›     cntdwn()›     index=0 ; back to scan line zero›     [›     $4C xitvbl ; jmp xitvbv›     ]›RETURN ; never gets here›; **********************************›PROC strini() ; initialize stars›   BYTE counter›   ; set up screen memory address tables›   ; first use dummy array for simplicity›   FOR counter=0 to 15›   DO›      strtp(counter)=strlin+48*counter›      strpos(counter)=0 ;all stars start at pos. zero›   OD›   ; now transfer addresses to byte arrays›   FOR counter=0 to 16›   DO›      strtpl(counter)=strtp(counter)&255›      ; cannot divide numbers>32767 and get correct results›      strtph(counter)=strtp(counter) RSH 8›   OD›   ; clear star memory›     ZERO(strlin,768)›   ; give each line a star›   FOR counter=0 to 15›   DO›      strlin(48*counter)=64›   OD›   RETURN›; ***********************************›PROC dlsini() ; initialize display list›   BYTE startype,offset,counter›   CARD TEMP›   ; do for each scan line›   dlist(0)=$70 dlist(1)=$70 dlist(2)=$F0›   FOR counter=0 to 191›   DO›      dlist(3*(counter+1))=$CE ; graphics 7+›      ; now pick star type›      startype=RAND(8)›      ; set color for each line›      strcol(counter)=mancol(startype)›      ; randomize offset into memory›      offset=RAND(48) ;offset into line›      ; now put address of line into display list›      dlist(3*(counter+1)+1)=(strtp(2*startype)+offset)&255›      ; cannot divide numbers>32767 and get correct results›      dlist(3*(counter+1)+2)=(strtp(2*startype)+offset) RSH 8›   OD›   ; now finish up display list›   dlist(579)=$41 ; jump instruction›   dlist(580)=dlist&255›   dlist(581)=dlist RSH 8›   sdlstl=dlist ;tell antic where display list is›   sdmctl=$23 ;wide screen›RETURN›; ***********************************›PROC dli() ; display list interrupt routine›; too little time to even think about using ACTION!›   [›   $AE INDEX ; LDX INDEX›   $BD $FFFF ;LDA STRCOL,X›   $8D WSYNC ; STA WSYNC›   $8D COLPF0 ; STA COLPF0›   $EE INDEX  ; INC INDEX›   $40 ;RTI›   ]›RETURN›;************************************************************›PROC MAIN()›   ; fix up ml routines›   ; by poking in addresses of various arrays›   POKEC(dli+4,strcol)›   POKEC(scroll+7,strtpl)›   POKEC(scroll+12,strtph)›   POKEC(scroll+17,strpos)›   POKEC(scroll+40,strpos)›   POKEC(DLI+1,@index)›   strini() ;set up stars›   dlsini() ;set up display list›   color4=0 ;set background color›   SETVBV(7,vblank/256,vblank&255) ; set up vblank›   vdslst=dli  nmien=192 ; get dli's going›   ; now just let things run›   DO››   OD›RETURN›