CODING - the procedure "plasma balls".

SoundTrack: "F.T." BY SEC70R/SSG 4 DEJAVU # 3
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(C) Kolotov Sergei, SerzhSoft, 01.03.98.
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            PLASMA BALLS



                     Not everything - sun,

                         that rises ...


   Remember VIBRATIONS?! Well, the demo with the Enlight-96, 
which is still almost won the first place. Today we examine one 
of the two attribute effects, which were presented in this 
paper. How it all might have guessed from the title, we will 
talk about plasma balls. Let me remind you looked like this 
steep for the time effect. 


   On a black screen fly two attribute
colored ball, which upon application
each other form new colors, vzaimoslivayutsya. As any two 
protein clot.



   In that distant time, the attribute effects
are just beginning to "unwind", and
plasma is then just started its triumphal procession ... One of 
the original ideas that have been applied in "Vibration" was 
that that on the screen before displaying the attributes of the 
schedule was filled with rare "mesh" that softens the colors 
and the picture is not so like "a bunch of colored squares. 


   It should be noted that this effect with the balls still in 
my opinion, one of the best attribute effects. Moreover, 
plasma-it is hard to like this, on the move had called!



   The effect produced on me so bright
the impression that I, without hesitation, he climbed
inside the demo to look at the "cool code. Hmm ... "A king is 
naked!" Cheats were not written on this too ruleznom level that 
one would expect! "Not so cool as he is painted!" - I thought, 
and downloaded the ZX-ASM - "What are we, Siberians, worse?". 
:-) I took, and wrote his variant of this effect. And what do 
you think? Happened only 428 bytes suprotiv 1105!

But turn to the description of the algorithm ...


   First, we led the special buffer
under the shadow screen size of 64 * 64 = 4096
bytes. In this "shadow businesses" normal attribute the screen 
will correspond to a rectangle 32 * 24, located in the center. 
Output and clean, we'll only this rectangle, while the balls are

drawn around the shadow screen.


   Second. Balls are derived as follows: take byte color balls 
and added to the byte in the shadow screen. The result is 
placed there too. The idea: Why we do not create a special 
realtime-procedure, which draws on the tricky balls. A it 
happens like this: 1. Register HL points to the upper left

Drawn angle of the ball in the shadow screen
2. Ball derive along the lines of
3. Null bytes are simply skip
4. Blue color output of the command INC (HL)
5. Red - the two INC (HL)
6. Magenta - LD A, B: ADD A, (HL): LD (HL), A
7. Green - LD A, C: --//- 8. Blue - LD A, D: --//- 9. Yellow - 
LD A, E: --//- 10. All other colors (white and non-zero 
PAPER'om) we deduce about this way (simplified): 

        INC E

        LD A, E: ADD A, (HL): LD (HL), A

        ...

        LD A, E: ADD A, (HL): LD (HL), A

        ...

        DEC E
11. Before calling the procedure set
registers BC = # 0304, DE = # 0506



   Third. Compliance procedures output images with shadow 
screen to the real and clearing all the same "shadow 
businesses." First - 16 times POP HL: LD (...), HL, and then - 
too 16 times, but PUSH DE, pre-setting DE = # 0000.




   By the way! Indeed, this effect works in
48 kbps! And sync "on beam" it is not
need - time to all computers.


   It will be shown on the assembler listing with a few 
comments. All their program I am writing to ZX-ASM'e. But since 
Many have respect for other assemblers, the annex you will find 
a listing for the effect in a simple text format (end of line - 
# 0D, # 0A). When you load the same in his ZX-ASM you can 
simply click Import and then have to compile the program ... 
Adherents of other assemblers will have to sweat a little with 
conversion if necessary translation software available. 


   Take a look closer to listing
program. Initially, we allow interrupts. It is necessary to 
execute the command processor HALT, which waits for interrupts, 
and this case, waiting for the start of the beam

Monitor building a picture on the kinescope.


   This is followed by the initialization procedure call. But 
since procedures follow one the other, then you can leave just 
one CALL, and subsequent to remove, as commands RET

in all procedures, except the last. (For
readability and debugging better not
delete, and mark it as comment.)


   INITSCR procedure clears the screen, making
and fills it with black graphics "mesh"
of the points for a smooth transition of colors.


   INITBLS procedure initializes the table of coordinates and 
velocities of the balls. In total, we have a 4 "stack" 
variables to 5 bytes (Two balls in two coordinates). Rate of 
change of the coordinates are copied from the table BLS_DAT. 



   MK_OUTC procedure is programmed in realtime and creates a 
combined procedure for rapid display an image on screen is real 
and cleaning of the shadow. (OUTCLR2) 



   Procedure MK_PUTB initially in the buffer draws top half 
colored ball using a "floating overflow

borders. "Then you draw a part is mirrored, and get a ball. 
Then, using the received image fast realtime-generated procedure

O pen on the shadow screen. (PUTBALL)



   In the main loop program, we wait until
beginning of the beam (HALT), then we deduce
image with a shadow screen and clear
it (CALL OUT_CLR). The next step the new coordinates are 
counting beads and paint their shadow on the screen (PUT_BLS). 
Cycle is interrupted by pressing SPACE, after which we return 
to a place call (BASIC, assembler ...). 


   Well you probably already can not wait
download the assembler, so time for me to call it a day ... 
Hope you enjoyed it ... 


   With all the suggestions, concerns,
suggestions, please contact:


   641800, Kurgan region., G.Shadrinsk,

      st. Karl Liebknecht, 27, kv.1.

      Kolotova Sergei Sergeyevich.



   All of your letters carefully considered and, if possible, I 
try to answer them.



                       With best wishes

                                    Serzh.