==============================>
^|||||| PROGRAMMING ||||||`
'\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ @
________________________________
Konstantin Limonov (Smoke / CLV).
________________________________
Hello to all fans of assembly! In this issue, I
(Smoke) I want to offer your
attention to the procedures of a small but
very expressive -
"Flying Sprite!
________________________________
Such an effect you probably have seen
the heap and any INTRO MUSICDEMO.
Assembler these procedures look different, but the principle of
action they have almost the same. I imagine my
variant.Konechno, he is not the best and effective, but the
most simple and intuitive to each nachinayuschimu koderu.Vse
line program are numbered and you can see a detailed commentary
on each of them after the text itself
programmy.Itak begin ...
________________________________
FLY LD DE, # 0000 2000
CALL CL_SP 01
PTX LD HL, POX 02
LD A, (HL) 03
CP # FF 2004
JR NZ, LIP1 05
LD HL, POX 06
LD (PTX + # 01), HL 07
JR PTX 2008
LIP1 LD D, A 09
PTY LD HL, POY 1910
LD A, (HL) 11
CP # FF 1912
JR NZ, LIP2 13
LD HL, POY 1914
LD (PTY + # 01), HL 15
JR PTY 16
LIP2 LD E, A 17
CALL PLOT 18
LD (FLY + # 01), HL 19
PUSH HL 1920
LD DE, SPSIZE 21
LD HL, SPRT-SSIZE 22
LIP3 ADD HL, DE 23
DJNZ LIP3 24
POP DE 1925
CALL GET_SP 26
LD HL, (PTX + # 01) 27
INC HL 28
LD (PTX + # 01), HL 29
LD HL, (PTY + # 01) 30
INC HL 31
LD (PTY + # 01), HL 32
RET 1933
PLOT LD A, # AF 34
SUB E 35
AND A 36
RRA 37
SCF 38
RRA 39
AND A 40
RRA 41
XOR E 42
AND # F8 1943
XOR E 44
LD H, A 45
LD A, D 46
RLCA 47
RLCA 48
RLCA 49
XOR E 50
AND # C7 51
XOR E 52
RLCA 53
RLCA 54
LD L, A 55
LD A, D 56
AND # July 1957
LD B, A 58
INC B 59
RET 1960
GET_SP LD B, VIS * # August 1961
LIP4 PUSH DE, BC 62
LD B, DLINA 63
LIP4_X PUSH BC 1964
LDI 1965
POP BC 1966
DJNZ LIP4_X 67
POP BC, DE 1968
CALL DE_LINE 69
DJNZ LIP4 70
RET 1971
CL_SP LD BC, VIS * # 800 72
LIP5 PUSH BC, DE 1973
XOR A 74
LD B, DLINA 75
LIP6 LD (DE), A 76
INC DE 1977
DJNZ LIP6 78
POP DE, BC 79
CALL DE_LINE 80
DJNZ LIP5 81
RET 1982
;------------------------------ DE_LINE INC D 83
LD A, D 84
AND # July 1985
RET Z 86
LD A, E 87
ADD A, # 20 88
LD E, A 89
RET C 90
LD A, D 91
SUB # August 1992
LD D, A 93
RET 1994
;------------------------------ SPRT INCBIN SPRITES 95
POX INCBIN COORD-X 96
POY INCBIN COORD-Y 97
;------------------------------ Now consider this procedure
more podrobno.Itak, starting with the 0-th
stroki.V this line in the register pair DE loading address in
display area, where at a given
moment is sprayt.Zatem in
line 01 is invoked procedure
erase sprayta.Pri this image is under the sprite
teryaetsya.Poetomu would be better if you are not situated on
place where it will "fly" sprite
some graphical information.
On line 02, in the register pair
HL send the address of the
Table coordinate axis 'X'.
(For instructions on how to prepare a table of coordinates, you
can read below). In the battery load coordinates from a
spreadsheet and produced check at the end of the table (code
end of the table is the number of
# FF (255 DEC)). If this is the end
table, the row 02 being upgraded so that the register pair HL
is set top the table of coordinates. If it is one of the
coordinates, then transition occurs on line 09.
The resulting X-coordinate is
transferred to the register of D. Then
is similar to loading
and checking the coordinates of Y. In the transition to line
17, we are Register D coordinate X, and coordinate in register
E Y. Next, at 18 prompt a call to the procedure takes a string
PLOT.Ona 34 th to the 60 yu.Protsedura PLOT engaged in the
calculation of addresses in the display area at coordinates
defined in pikselah.V register pair HL, it returns the address
in the display area, and in the case B number of the sprite,
which must this time printed on the screen
monitora.Vnimanie! The program uses the same sprites 8
width and height, but each
sprite is shifted relative
the previous one pixel vpravo.Eto necessary for smooth
move the sprite left and
vpravo.Pochemu sprites eight??
Yes, because a byte is
of eight bits! Prepare
a set of sprites can, in
Basically, in ART-STUDIO, but better
use for this, for example,
program of Digital Reality
- "SpriteLand v1.xx". But keep in mind
that zdvige sprite, its width will increase by one character (!)
Remember this! When the program is also necessary to know the
length of one sprite in bytes.
After calculating the coordinates of the address, he entered
into line 00, where he needed to erase sprayta.Posle this same
address is sent to the stack, and in lines 21 th to 24 th of
searching desired sprite from the table and then restoring the
address of the press, line 26, is a challenge
procedures for printing a sprite.
The printing process is a sprite on the screen takes a line
from 61 th to 71-yu.Ona easy to predela.V
line 61 to the register B is loaded height of your sprite
familiarity multiplied by eight. After all, familiarity in one
8-NIL lines, is not it? The next line store registers DE and
BC, and then organized another round of
Print each line sprayta.V principle, you can uncover
this cycle of erasing the line with the 63rd
on 67-th, instead type
in this place so many teams LDI,
much familiarity in width takes your sprayt.Dalee, in line
68 th, restored registers
BC and DE, but then comes the challenge procedure for
calculating the addresses of Print next line of the sprite
under predyduschey.Eta procedure is so well known and simple,
that describe how it works just bessmyslenno.Luchshe Read the
book "Inforkom'A: "Elementary graphics", "Applied Graphics" and
"Dynamic schedule. "And, of course, ZX-REVIEW!
With the line 72 th to 82 th is erasing procedure sprayta.Ona
works on the same principle as the how to print sprayta.Nu,
generally, will understand! And then I'll I'll die for klav'oy
from such mental stress.
____________
Well it's time to tell you how to make a table of coordinates
which will "fly" your sprite. In the annex of the magazine you
will find small program in BASIC,
which will help you in the first
porah.Potom, based on it, you can create something called
svoe.Ona - LISSADGU, and builds, so called the figure
Lissazhu.Chtoby understand what is at stake, one should at
least know a little elektrotehniku.Tak here, the objects that
appear as a result of program on the screen, and there are those
most figures Lissazhu.Programma
has several variables:
________________________________
'K' - multiplicity.
'G' - a phase shift.
'A1' and 'A2' - amplitude.
________________________________
Try to enter, such
parameters: K [5, G [0, A1 [110, A2 [70,
or are: K [2, G [1, A1 [90, A2 [75, and
once everything is clear! Only
Remember the one condition - sprite
will be printed starting from the upper left corner, and in
those points, which will be shown
on the screen! So watch out for
so that your sprite is not got a
edge of the screen (on the curb! Joke!)!
Make corresponding indentation
for as many pixels as a wide your sprite! Well, after the
programm will prompt you to save the created table to disk, you
can safely substitute their names in the assembly code in line
96 and 97.A in line 95, substitute the name you created on the
table spraytov.I This, perhaps, could be zakonchit.Good luck,
young coders!
________________
CUL8R! Written by Smoke
18/11/97-00: 07
________________
P.S. The name of the assembly file for
CD: (SPRFLY).
