Move sprite to X,Y (as LINE) in assembly

It's a bit hard to follow your explanation... Do you want to linearly interpolate the place of a missile from (x0,y0) to (x1,y1) in assembly or what? Or get the direction for the missile from the ship's current location (which is pretty much the same anyway)?

Hey, this page is empty for adding comment ?
DanySoft

If the following conditions are satisfied, the sample code of aredbook is correct.

Y2 >= Y1
X2 >= X1
ABS(X2-X1) >= ABS(Y2-Y1)

Therefore, depending on the above three conditions,
- Write eight subroutines
or
- Branch process in detail
(swap X1 and X2, etc.)

Or, I modified the sample code. However, non-integer values are used.

10 SCREEN 0
20 INPUT"START X,Y";X1,Y1
30 INPUT"END X,Y";X2,Y2
40 SCREEN 2
50 X=X1:Y=Y1:LX=ABS(X2-X1):LY=ABS(Y2-Y1)
60 IF LX>LY THEN L=LX ELSE L=LY
65 ' "L=SQR(LX*LX+LY*LY)" is the better for MISSILE ???
70 DX=(X2-X1)/L:DY=(Y2-Y1)/L
80 PSET(X+0.5,Y+0.5)
90 X=X+DX:Y=Y+DY:IF ABS(X-X1)<=LX AND ABS(Y-Y1)<=LY THEN 80
100 LINE(X1,Y1+5)-(X2,Y2+5)
110 GOTO 110

DX or DY maybe not integer. (example: 0.7, -0.1, 0.333333... , etc.)
Therefore, DX or DY cannot be in one register.
Two (or more) registers are used for DX or DY. It is complicated.

You can use the other way. " Write eight subroutines"

10 SCREEN 0
20 INPUT"START X,Y";X1,Y1
30 INPUT"END X,Y";X2,Y2
40 SCREEN 2
50 FLAG=0
60 IF Y2 >= Y1 THEN FLAG=FLAG+1
70 IF X2 >= X1 THEN FLAG=FLAG+2
80 IF ABS(X2-X1) >= ABS(Y2-Y1) THEN FLAG=FLAG+4
90 ON FLAG+1 GOSUB 200,300,400,500,600,700,800,900
100 LINE(X1,Y1+5)-(X2,Y2+5)
110 GOTO 110
200 ' Y2 < Y1 , X2 < X1 , ABS(X2-X1) < ABS(Y2-Y1)
210 X=X1:Y=Y1:L=Y1-Y2:S=X1-X2:CTR=L/2
220 PSET(X,Y)
230 CTR=CTR+S:IF CTR < L THEN 250
240 CTR=CTR-L:X=X-1
250 Y=Y-1:IF Y>=Y2 THEN 220
260 RETURN
300 GOSUB 1000 : RETURN
400 GOSUB 1000 : RETURN
500 ' Y2 >= Y1 , X2 >= X1 , ABS(X2-X1) < ABS(Y2-Y1)
510 X=X1:Y=Y1:L=Y2-Y1:S=X2-X1:CTR=L/2
520 PSET(X,Y)
530 CTR=CTR+S:IF CTR < L THEN 550
540 CTR=CTR-L:X=X+1
550 Y=Y+1:IF Y<=Y2 THEN 520
560 RETURN
600 GOSUB 1000 : RETURN
700 GOSUB 1000 : RETURN
800 GOSUB 1000 : RETURN
900 ' Y2 >= Y1 , X2 >= X1 , ABS(X2-X1) >= ABS(Y2-Y1)
910 X=X1:Y=Y1:L=X2-X1:S=Y2-Y1:CTR=L/2
920 PSET(X,Y)
930 CTR=CTR+S:IF CTR < L THEN 950
940 CTR=CTR-L:Y=Y+1
950 X=X+1:IF X<=X2 THEN 920
960 RETURN
1000 SCREEN 0
1010 PRINT"under construction..."
1020 STOP
1030 END

And....
i'm use the formul of ASM of use angle to °360:
use this for my game as "TANK"....

You see "M-Tanks" : this game is creating by autor:"Assembler" !
Make sprite from tank to tank is great !

The sorcery is necessary for three part:

1. Check Location of X,Y on TANK:
2. calculation position and long from two tank
3. fire the ball from tank to tank (example: 30° is position X,Y on TANK)

This sorcery is necessary for future GAME !! But This BASIC is slow....... and use XBASIC for FAST SPEED on GAME,
and single GAME are 16K from ROM o RAM!!!!!

and then my game is different from his own:
is installed cannons and machine guns from the ground, and rotate 360 ° was easy!

DanySoft