;----------------------------------------------------------------------------- ; ; TITLE: Star field ;WRITTEN BY: DRAEDEN ; DATE: 03/15/93 ; ; NOTES: Need 386 to execute. ; ;ASSOCIATED FILES: ; ; STARGEN.BAS => Basic program that generates a set of 'randomized' ; numbers. Creates STARRND.DW ; ; STARS.TXT => The text file that explains starfields... ; ; STARRND.DW => File that contains a set of shuffled numbers. ; Used to create 'random' star field. ; ;---------------------------------------------------------------------------- DOSSEG .MODEL SMALL .STACK 200h .CODE .386 ASSUME CS:@CODE, DS:@CODE ; LOCALS ;=== GLOBALS ;=== Data Includes INCLUDE starrnd.dw ;file that has label StarRnd numbers ;=== DATA Structures Star_Struc STRUC X dw 0 Y dw 0 Z dw 0 OldDi dw 0 ;where to erase last dot Color db 0 ;BASE color. a number 0-16 is added to it Star_Struc ENDS StarStrucSize = 9 ;number of bytes per entry ;=== DATA ScreenWidth EQU 320 ScreenHeight EQU 200 NumRnds EQU 400 ;number of random numbers defined MaxZpos EQU 4096 MinZpos EQU 2 MaxStars EQU 190 NumColors EQU 5 ;number of Base colors in the Color Chart WarpSpeed dw 15 ;how quickly the stars move toward ya MaxWarp EQU 90 Xindex dw 30 ;index into the StarRnd chart for X & Y Yindex dw 230 ; -note they must be different; set em the same to ;see why Cindex dw 0 ;index into ColorChart ColorChart db 0,16,32,48,64,80 ;a list of base colors (-1) Stars Star_Struc MaxStars DUP (<>) ;where all the data is held NumActive dw 0 ;number of stars active Palette db 3 dup (0) ;the palette.. first entrie is BG color (black) i = 15 REPT 16 db 2*i,3*i,4*i i=i-1 ENDM i = 15 REPT 16 db 2*i,2*i,4*i i=i-1 ENDM i = 15 REPT 16 db 3*i,3*i,4*i i=i-1 ENDM i = 15 REPT 16 db 3*i,2*i,4*i i=i-1 ENDM i = 15 REPT 16 db 3*i,3*i,3*i i=i-1 ENDM i = 15 REPT 16 db 2*i,4*i,3*i i=i-1 ENDM ;=== Code Includes ;=== SUBROUTINES ;finds 1st available slot for a star and puts it there MakeStar PROC NEAR pusha mov ax,cs mov es,ax mov ds,ax cmp [NumActive],MaxStars ;is there room for another star? jae NoEmptySpace ;search for 1st available slot mov si,0 TryAgain: cmp word ptr [Stars.Z+si],0 ;is this slot empty? je GotOne ;yes, go fill it add si,StarStrucSize cmp si,MaxStars*StarStrucSize jb TryAgain jmp NoEmptySpace GotOne: ;si points to the record for the star to fill mov di,[Yindex] ;grab index for Ypos add di,di ;multiply by 2 to make it a WORD index mov ax,[StarRnd+di] ;get the number shl ax,3 ;multiply by 8- could been done in BAS file mov [Stars.Y+si],ax ;and save off the number mov di,[Xindex] ;grab index for Xpos add di,di ;... same as above, but for Xpos mov ax,[StarRnd+di] shl ax,3 mov [Stars.X+si],ax mov [Stars.Z+si],MaxZpos ;reset Zpos to the max inc [NumActive] ;we added a star so increase the counter mov di,[Cindex] ;grab the color index mov al,[ColorChart+di] ;grab the BaseColor for the star mov [Stars.Color+si],al ;save it in the record ;increase all the index pointers inc [Cindex] ;increases the color counter cmp [Cindex],NumColors jb OkColor mov [Cindex],0 OkColor: inc [Yindex] ;increases Yindex cmp [Yindex],NumRnds ;note that for this one we jb YindNotZero ; subtract NumRnds from Yindex if we sub [Yindex],NumRnds ; go off the end of the chart YindNotZero: inc [Xindex] ;increase Xindex cmp [Xindex],NumRnds ;have we gone through the entire chart? jb XindNotZero ;nope... ;This clever bit of code makes more use out of the chart by increasing Yindex ; one additional unit each time Xindex goes through the entire chart... the ; result is nearly NumRND^2 random non-repeating points inc [Yindex] ;yes, so change Yindex so that we get a mov ax,[Yindex] ;new set of random (x,y) cmp ax,[Xindex] ;does Xindex = Yindex? jne NotTheSame ;if the index were the same, you'd see ;a graph of the line Y = X, not good... inc [Yindex] ;if they are the same, inc Yindex again NotTheSame: mov [Xindex],0 ;reset Xindex to 0 XindNotZero: ;all done making the star... NoEmptySpace: popa ret MakeStar ENDP DisplayStars PROC NEAR pusha mov ax,cs mov ds,ax mov ax,0a000h mov es,ax mov si,0 DispLoop: mov cx,[Stars.Z+si] or cx,cx ;if Zpos = 0 then this star is dead... je Cont ;continue to the next one- skip this one mov di,[Stars.OldDi+si] ;grab old Di mov byte ptr es:[di],0 ;erase the star cmp cx,MinZpos jl TermStar ;if Zpos < MinZpos then kill the star mov ax,[Stars.Y+si] movsx dx,ah ;'multiply' Ypos by 256 shl ax,8 idiv cx ;and divide by Zpos add ax,ScreenHeight/2 ;center it on the screen mov di,ax cmp di,ScreenHeight ;see if the star is in range. jae PreTermStar ; If not, kill it imul di,ScreenWidth ; DI = Y*ScreenWidth mov ax,[Stars.X+si] movsx dx,ah ;multiply Xpos by 256 shl ax,8 idiv cx ;and divide by Zpos add ax,ScreenWidth/2 ;center it on the screen cmp ax,ScreenWidth ;are we inside the screen boundries? jae PreTermStar add di,ax ; DI = Y * ScreenWidth + X mov [Stars.OldDi+si],di ;save old di ;calculate the color below add ch,cs:[Stars.Color+si] ;i'm dividing cx (the zpos) by 256 and ; putting the result in ch and adding ; the base color to it in one instruction mov es:[di],ch ;put the dot on the screen mov ax,cs:[WarpSpeed] sub cs:[Stars.Z+si],ax ;move the stars inward at WarpSpeed Cont: add si,StarStrucSize ;point to next record cmp si,MaxStars*StarStrucSize ;are we done yet? jb DispLoop popa ret PreTermStar: mov [Stars.Z+si],1 ;this is here so that the star will get erased jmp short Cont ;next time through if I just went off and killed ;the star, it would leave a dot on the screen TermStar: mov [Stars.Z+si],0 ;this actually kills the star, after it has dec [NumActive] ;been erased jmp short Cont DisplayStars ENDP ;=== CODE START: mov ax,cs mov ds,ax mov es,ax mov ax,0013h ;set vid mode 320x200x256 graph int 10h mov dx,offset Palette mov ax,1012h ; WRITE palette mov bx,0 mov cx,256 ;write entire palette int 10h ;doesn't matter if we didnt define it all StarLoop: call MakeStar ;make stars 2x as thick call MakeStar mov dx,3dah VRT: in al,dx test al,8 jnz VRT ;wait until Verticle Retrace starts NoVRT: in al,dx test al,8 jz NoVRT ;wait until Verticle Retrace Ends call DisplayStars mov ah,1 ;check to see if a char is ready int 16h jz StarLoop ;nope, continue mov ah,0 int 16h ;get the character & put in AX cmp al,"+" ;compare ASCII part (al) to see what was pressed jne NotPlus inc [WarpSpeed] cmp [WarpSpeed],MaxWarp jbe StarLoop mov [WarpSpeed],MaxWarp jmp StarLoop NotPlus: cmp al,"-" jne NotMinus dec [WarpSpeed] cmp [WarpSpeed],0 jge StarLoop mov [WarpSpeed],0 Jmp StarLoop NotMinus: mov ax,0003h ;set 80x25x16 char mode int 10h mov ax,4c00h ;return control to DOS int 21h END START