** CODE ASTEROID FIELD ** CODER MARC .B ** THANK'S TO MIKE CROSS ** FOR HIS EXCELLENT SPRITE TUTORIAL AND STAR-FIELD CODE ** ; this code attempts to recreate the asteroid field effect ; seen in many games like lunar lander etc..... *** system calls *** execbase equ 4 openlibrary equ -408 closelibrary equ -414 allocmem equ -198 freemem equ -210 forbid equ -132 permit equ -138 copymem equ -624 *** constants *** chip equ 2 clear equ $10000 number_field equ 12 max_speed equ 2 *** include hardware.i *** include source:include/hardware.i lea $dff000,a5 ;custom base address ********************************************************** * OPEN GFX LIBRARY AND SAVE SYSTEM COPPER * ********************************************************** move.l execbase,a6 move.l #gfxname,a1 moveq #0,d0 jsr openlibrary(a6) tst d0 beq the_end move.l d0,gfxbase move.l d0,a0 ;put gfxbase in a0 move.l 38(a0),systemcopper ;save the copper address **************************************************** * ALLOCATE MEMORY FOR BIT PLANES * **************************************************** move.l execbase,a6 move.l #(320/8*256)*2,d0 ;memory for 2 bitplanes move.l #chip+clear,d1 ;chip memory and wipe it jsr allocmem(a6) tst d0 ;fail beq exit ;yep move.l d0,bitbase ;save pointer ******************************************************* * ALLOCATE MEMORY FOR ASTEROIDS * ******************************************************* move.l execbase,a6 move.l #number_field*spritelen,d0 ;total bytes needed move.l #chip+clear,d1 jsr allocmem(a6) ;get the memory tst d0 ;course it worked beq exit1 ;no it didn't move.l d0,spritebase ;save sprite address ********************************************************* * COPY SPRITES TO MEMORY * ********************************************************* copy_sprites move.l #number_field-1,d7 move.l spritebase,a1 copy_loop move.l #sprite,a0 move.l #spritelen,d0 move.l execbase,a6 jsr copymem(a6) dbf d7,copy_loop ***************************************************************** * LOAD BITPLANE AND SPRITE POINTERS INTO COPPER LIST * ***************************************************************** move.l bitbase,d0 lea copper,a0 move.w d0,6(a0) ;load bitplane pointers into c list swap d0 move.w d0,2(a0) swap d0 add.l #$2800,d0 move.w d0,14(a0) swap d0 move.w d0,10(a0) swap d0 move.l spritebase,d1 ;load sprite pointer into c list move.w d1,22(a0) swap d1 move.w d1,18(a0) swap d1 ********************************************************************* * MAKE ASTERIOD FIELD * ********************************************************************* setup_field move.l spritebase,a0 ;address of sprite memory move.w #number_field-1,d7 ;set loop counter move.w #75,d0 ;initial y position move.l #0,d2 ;set y overflow flag to zero move.w #$301f,d3 move.w #$5512,d5 ;random number seeds make_field move.w VHPOSR(a5),d4 or.l d3,d5 add.l d4,d5 move.b d0,(a0)+ ;y position ( 1st control word) move.b d5,(a0)+ ;x position (random) add.w #13,d0 ;incrememt y position move.b d0,(a0)+ ;set display stop byte (2nd ctrl word) move.b d2,(a0)+ ;set y overflow add.w #52,a0 ;point to next sprite add.w #3,d0 ;increase y position cmpi.w #238,d0 ;reached bottom of screen ? bls okay ;not there yet !! move.w #0,d0 ;reset y counter move.w #6,d2 ;set overflow flag okay dbf d7,make_field ;build till d7 = 0 *************************************************************** * START CUSTOM COPPER LIST * *************************************************************** move.l #copper,COP1LCH(a5) move.l #0,COPJMP1(a5) move.l execbase,a6 jsr forbid(a6) ************************************************************* * MAIN CODE LOOP * ************************************************************* wait move.l VPOSR(a5),d0 ;read current beam position and.l #$0001ff00,d0 ;mask all but the vertical pos lsr.l #8,d0 cmp.w #$0106,d0 ;wait for end of display bne wait bsr move_field ;move field btst #6,CIAAPRA ;check mouse button status beq clean_up ;exit if left button pressed bra wait ********************************************************** * RESTORE SYSTEM * ********************************************************** clean_up move.l systemcopper,COP1LCH(a5) move.l #0,COPJMP1(a5) move.l execbase,a6 jsr permit(a6) move.l execbase,a6 move.l #number_field*spritelen,d0 move.l spritebase,a1 jsr freemem(a6) exit1 move.l execbase,a6 ;free bitplane memory move.l #(320/8*256)*2,d0 move.l bitbase,a1 jsr freemem(a6) exit move.l gfxbase,a1 ;close the graphics library move.l execbase,a6 jsr closelibrary(a6) the_end rts ;exit from program *************************************************************** * MOVE ASTEROID FIELD * *************************************************************** move_field move.l spritebase,a0 move.w #(number_field/2)-1,d7 ;the number of stars is divided moveq.w #1,d1 ;by 2 because ths sprites are moved ;two at a time in the field_loop field_loop add.b d1,1(a0) ;move sprite right add.w #56,a0 ;point to next sprite sub.b d1,1(a0) ;move it left add.w #56,a0 ;point to next sprite addq.b #1,d1 ;increase speed cmpi.b #max_speed,d1 ;check it ble speed_okay moveq.b #1,d1 ;to fast reset speed counter speed_okay dbf d7,field_loop rts *********************************************************** * CUSTOM COPPER LIST * *********************************************************** SECTION copper.list,CODE_C copper dc.w BPL1PTH,0000 ;next 4 blank words dc.w BPL1PTL,0000 ;are where we load dc.w BPL2PTH,0000 ;the bitplane pointers dc.w BPL2PTL,0000 dc.w SPR0PTH,0000 dc.w SPR0PTL,0000 ;sprite 0 pointer dc.w SPR1PTH,0000 dc.w SPR1PTL,0000 ;sprite 1 pointer dc.w SPR2PTH,0000 dc.w SPR2PTL,0000 ;sprite 2 pointer dc.w SPR3PTH,0000 dc.w SPR3PTL,0000 ;sprite 3 pointer dc.w SPR4PTH,0000 dc.w SPR4PTL,0000 ;sprite 4 pointer dc.w SPR5PTH,0000 dc.w SPR5PTL,0000 ;sprite 5 pointer dc.w SPR6PTH,0000 dc.w SPR6PTL,0000 ;sprite 6 pointer dc.w SPR7PTH,0000 dc.w SPR7PTL,0000 ;sprite 7 pointer dc.l $2b01fffe ;wait for line 43 dc.w DIWSTRT,$2c81 ;where we start displaying dc.w DIWSTOP,$2cc1 ;where we stop! dc.w BPLCON0,$0200 ;this is for Amiga 1000 owners dc.w BPLCON2,$0024 dc.w DDFSTRT,$0038 ;where to start the horizontal display dc.w DDFSTOP,$00d0 ;and where we stop dc.w BPLCON1,$0000 dc.w BPL1MOD,$0000 ;not a scroller dc.w BPL2MOD,$0000 ;so these are blank dc.w COLOR00,$0000 ;background colour black dc.w COLOR01,$0fff ;colour 1 dc.w COLOR02,$0e00 ;colour 2 dc.w COLOR03,$00a1 ;colour 3 dc.w COLOR04,$0d80 dc.w COLOR05,$0c70 dc.w COLOR06,$0c71 dc.w COLOR07,$0b61 dc.w COLOR08,$0b62 dc.w COLOR09,$0a52 dc.w COLOR10,$0a52 dc.w COLOR11,$0fb0 dc.w COLOR12,$000f dc.w COLOR13,$0f00 dc.w COLOR14,$0f82 dc.w COLOR15,$0ff3 dc.w COLOR16,$0000 dc.w COLOR17,$0d80 dc.w COLOR18,$0b61 dc.w COLOR19,$0a52 dc.w COLOR20,$0333 dc.w COLOR21,$0444 dc.w COLOR22,$0555 dc.w COLOR23,$0666 dc.w COLOR24,$0777 dc.w COLOR25,$0888 dc.w COLOR26,$0999 dc.w COLOR27,$0aaa dc.w COLOR28,$0ccc dc.w COLOR29,$0ddd dc.w COLOR30,$0eee dc.w COLOR31,$06f8 dc.l $2c01fffe ;wait for line 44 dc.w BPLCON0,$2200 ;turn on bit planes dc.l $fffffffe ;wait for the impossible endcopper copperlen equ endcopper-copper ************************************************************ * SPRITE DATA SECTION * ************************************************************ sprite dc.w $0000,$0000 SPRxPOS,SPRxCTL dc.w $0000,$0000 dc.w $0080,$0080 dc.w $03d0,$00c0 dc.w $0258,$0040 dc.w $36d8,$0000 dc.w $3cdc,$0010 dc.w $6fba,$0638 dc.w $37b3,$3300 dc.w $1dbb,$1180 dc.w $1ee2,$1000 dc.w $0126,$0000 dc.w $00dc,$00c0 dc.w $0070,$0060 endsprite spritelen equ endsprite-sprite ************************************************************ * VARIABLES * ************************************************************ gfxbase dc.l 0 bitbase dc.l 0 systemcopper dc.l 0 spritebase dc.l 0 gfxname dc.b 'graphics.library',0 end