Studies - Graphic effect "plasma".

          2. "Plasma"


   This is a series of beautiful effects. Here is the first of 
them, the simple:

140.
;--------------------------;
3; (c) Ivan Roshchin, 1997;
; EFFECT "PLASMA";
;--------------------------;


        LD HL, # 4000; CLS

        LD (HL), L

        LD DE, # 4001

        LD BC, # 1AFF

        LDIR

; Transfers the contents of the upper row
; Down and vice versa, ie screen like
; Closed vertically:

M2 LD HL, # 5820

        LD DE, # 5AE0

        LD BC, 32

        LDIR

        LD HL, # 5AC0

        LD DE, # 5800

        LD BC, 32

        LDIR

; In the cycle of updating the attributes # 5820 - # 5AE0:


        LD IX, # 5820
M1 LD A, (IX +1)

        ADD A, (IX-1)

        ADD A, (IX +32)

        ADD A, (IX-32)


        DEC A;!

        SRL A;!

        SRL A;!


        LD (IX), A

        INC IX

        LD A, XL

        CP # E0

        JR NZ, M1

        LD A, XH

        CP # 5A

        JR NZ, M1


        XOR A

        IN A, (254)

        CPL

        AND 31

        JR Z, M2

        RET
2

   You can experiment
with this program, changing it
region marked "!". Try these options:

a) DEC A b) SRL A in) SRL A

   SRL A DEC A SRL A

   SRL A SRL A DEC A

d) SRL A g) ADD A, 8

   SRL A SRL A

   INC A SRL A

               DEC A


   After this section you can add a command AND # 3F, or AND
# 7F - it also affects the type of effect.


   You can change or other piece of software:


        LD A, (IX +1)

        ADD A, (IX-1)

        ADD A, (IX +32)

        ADD A, (IX-32)

He determines that the value of current attribute depends on 
the values of attributes on the left, right, top and bottom 
of it: 



            - The current attribute


            - Contribute to it attributes



   Interesting results were obtained when determining these 
dependencies: 


     LD A, (IX +1) LD A, (IX)

     ADD A, (IX) ADD A, (IX)

     ADD A, (IX +32) ADD A, (IX +31)

     ADD A, (IX-32) ADD A, (IX +32)



     LD A, (IX-33) LD A, (IX)

     ADD A, (IX-31) ADD A, (IX)

     ADD A, (IX +31) ADD A, (IX +32)

     ADD A, (IX +33) ADD A, (IX +33)