Programming - Not the slowest procedure for displaying 2*2 sprites with pixel accuracy.

Especially for the Surgeon and
Blaster.

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  Not the slowest procedure
output sprites 2*2 with precision
to the pixel.

  A little theory.  How probably
It’s already clear to everyone that if a sprite
decompose into dots and output
by points, then it will slow down
scary, that's why they use it
all sorts of tricks.

  There is a 2*2 familiarity sprite. By
it’s easy to move it vertically, but
here horizontally... So,
prepare 8 sprites in advance
2*3 familiar places, moved in advance
move horizontally, and then you-
we drive the right one.  But it'll do
only when there are no sprites
a lot.  What if there are 50 of them?
2*3*8 - size of one spr.2*Zzn.
There are 8 of them - 2*3*8*8. And in total - 50...
2*3*8*8*50=6*64*50=64*300=19200.
However, for a large program 50 this is
few, and not just sprites
The man is alive - Mouzon, the program itself.
There is only one conclusion - move the sprites to
withdrawal time. At the end of the section
you can also find the output program itself,
which displays the sprite by OR.
The program itself is not very complicated,
the main thing is to understand the idea. In prog three
main procedures:
 PTBL_S - shift 2 bytes from (hl) and
(hl+1) and res. in B',C',D'.
 PTBL_O - output 3 bytes to the screen
given that the screen is not
infinite.
 PTBL_D - because  in DE address in screen,
then this procedure shifts DE to
oneпиксель вниз.

HL-ADRESS SPRITE
B-COORD_Y (0..191)
C-COORD_X (0..255)

PTBL    CALL PTBL_A
        LD B,8*2
PTBLO   CALL PTBL_S
        CALL PTBL_O
        CALL PTBL_D
        LD A,D
        CP #58
        RET NC ;OUT OF SCR
        DJNZ PTBLO
        RET

PTBL_D  INC D ; DOWN_DE
        LD A,D
        AND 7
        RET NZ
        LD A,E
        ADD A,#20
        LD E,A
        RET C
        LD A,D
        SUB 8
        LD D,A
        RET

PTBL_O  PUSH DE
        EXX
        LD A,B
        EXX
        LD (DE),A
        INC E
        LD A,E
        AND 31
        JR Z,PTBL_O0 ;OUT OF SCR
        EXX
        LD A,C
        EXX
        LD (DE),A
        INC E
        LD A,E
        AND 31
        JR Z,PTBL_O0 ; -//-
        EXX
        LD A,D
        EXX
        LD (DE),A
PTBL_O0 POP DE
        RET

PTBL_S  LD A,(HL)
        INC HL
        EXX
        LD B,A
        EXX
        LD A,(HL)
        INC HL
        EXX
        LD C,A
        EXX
        LD A,C
        EXX
        LD D,0
PTBL_S0 AND A
        JR Z,PTBL_S1
        RR B
        RR C
        RR D
        DEC A
        JR PTBL_S0
PTBL_S1 EXX
        RET

PTLB_A  LD A,B
        RRCA
        RRCA
        RRCA
        AND #18
        OR #40
        LD D,A
        LD A,B
        AND 7
        ADD A,D
        LD D,A
        LD A,B
        RLCA
        RLCA
        AND #E0
        LD E,A
        LD A,C
        RRCA
        RRCA       RRCA
        AND #1F
        ADD A,E
        LD E,A
        LD A,C
        AND 7
        LD C,A
        RET

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  The end. Mad Z-Group (C)2000.
   Main  editor :  Slavik/ZGR.
    Music  made  by  uncnown.