Skyhigh 07 ch12 Mixed

                  mixed





    about the making of skyhigh #6.


howdy hackers, this is RAZ/CAMELOT with
some coder-info about the new oufit of
skyhigh.

at the time i was asked to do the new
outfit, i'd just finished coding the
camelot mag 'REVEALED' and i was sick
and tried of disc-mags. however, i deci-
ded to do it anyway. some days later i
recived a disc from biz kid containing
all the things i needed to make the mag.
at the time i'd allready decided to make
a desktop menu, and the disc contained
the graphics, music and 4 test chapters.
i started to code the mag on a quite
lazy wednesday and this is how i did it:

DAY 1.

 biz kid had drawn some icons for the
menu, but they was in a 'wrong' format
and i therefore had to manipulate them
a bit. they was drawn in the way:
+$00,+$40,+$80,+$c0 meaning icon 1 was
build of $01,$41,$81,$c1. but i needed
to put some letters in the charset as
well. i made a small program (in basic)
that re-arranged the icons into another
format (+$00,+$01,+$02,+$03. icon 1 =
$04,$05,$06,$07). finally i copied the
icons into char.pos $80-$ff. i'd now
made the lower half of the charset
free for some letters. biz kid had sent
me the letter-charset (this one) and i
now merged them into the lower half of
my menu-charset.
 the next thing i did was drawing the
frames for the windows. (yes they are
made by me !!! hurray, hurray i bet i'll
now enter the graphics charts!!). final-
ly i inverted the letters and copied
them into char.pos $40-$7f. i'd now got
2 set of letters: one normal and one in
revers. the next thing i did was to de-
sign the main-menu screen.
 the routines for moving the arrow and
selecting the icons was very easily done
because the main technique is simple:

first of all you transform the sprite-
coordinates into screen (x,y) coors.
the first y-spr coor visible on the
screen (below the top border) is #50
(#$32). therefore you subtract #$32 and
then all you have to do is dividing with
8. (the screen lines are 8x8 pixels wide
, and you want to determine at which
scr-pos the sprite is):

              lda ypos
              sec
              sbc #$32
              lsr a
              lsr a
              lsr a

the first x-spr coor visible is #24
(#$18), and that means that it's pos-
sible to subtract #$03 (3*8 =24 =#$18)
in the end. the main problem is the 9th
bit ($d010). this can be solved by using
some bit-manipulating:

              lda $d010
              and #%00000001 ;sprite 0
                             ;in this
                             ;example.
              lsr a  ;9th bit is rota-
                     ;ted into carry.
              lda xpos
              ror a  ;carry is rotated
                     ;into 8th bit.
              lsr a
              lsr a
              sec
              sbc #$03

and now you've got the spr-coors in scr-
coors. easy.

the next thing i did was to make some
tables with the x,y coordinates of the
icons (and of the value to be returned
if the icon is activated).

i made most of the menu fade up effects
this day and actually, this was what
took must time to do.

by the way: in this mag i DO NOT USE ANY
INTERUPTS AT ALL. heck knows why, i just
felt in the mood. (ok: it was the easies
way of doing it).

2.SAY:

i spent most of the time coding the fade
up effects of the upscroller. the main
techniques used are:

LOGO FADE UP:

the lo-res logo is covered with 14 x-
expaned black sprites. the sprites is
animated in a sequence which they disa-
pear revealing the logo. quite easy code
but it took me a while making everything
run 100% smooth (timing!!).

UPSROLLER:

 in order to make everything look/feel
smooth i placed 7 black sprites (8 pix-
els high) just below the headline. the
text then scrolls into coverage of the
sprites and disapears perfectly smooth.
i did it this way because i'm a lazy
person who prefer most thing the easies
way.
 when the text is faded in, all i do is
moving the black sprites from the bottem
and up lighting the textline under the
sprites.

the final thing i did this day was to
code the upscroller routine itself.
i haven't got much to say about the
upscroller it self but this: REMEMBER to
set $01 to the right value if some of
the text is placed 'underneath' the rom
($a000-$bfff, $e000-$ffff) or the i/o
area ($d000-$dfff).

3.DAY:

 well not much to say: this day i debug-
ged the whole thing (making all the up/
down fade routines work smoothly toget-
her was the hardest thing), installed
the loader/decrunch routine and finally
installed the musics.

 debugging is a boring event. very
boring. i just get so damn angry at my
own routines when they don't work the
way i want them to. arrrrrrgh. by the
way: i'd forgotten to set $01 to #$36
and therefore the text in the area
$a000-$bfff fucked up. bummer!.

 making the music run 100% smooth was a
bit hard (i don't use any interupts in
this mag, remember?), but as you see
(hear) i made it.

 finally i mailed it to biz kid.

LAST DAY:
 a few days (and some phonecalls) later
a recived a disc from the ever smiling
biz kid with some graphics that had to
be changed. only one hard thing among
this: the 8-colour fli sprite:

FLI SPRITE:

 i had to open the top/bottom border in
order to use this, and i had to make
some changes in my code. first of all:
now the border has gone missing i had to
place a row of 7 black sprites at the
last line of the screen. or else the
text couldn't disapear properly at the
bottom. however, the fli sprite was to
be placed a few pixels below this row,
and i therefore placed the black pixels
in the lowest part of the sprite.
 ofcause this isn't hard in theory, but
it takes quite a few tries to make look
good and to debug.

by the way: i also changed the colours
of the main menu this day. (the old ones
was red/yellow. looking good, but hard
to see).

the version finished this day is the one
used in skyhigh #6. MADE IN 4 DAYS.


 it was quite fun to make and you hope
you'll enjoy it as much as i do.

26/9 1993.                        -RAZ.

 -- -- -- -- -- -- -- -- -- -- -- -- --
ps.

 i'll continue this chapter in the next
issue, with some words about the updated
code in issue 7.
 furthermore, i'll start up my chapter
about assembler programming in the next
issue also.

        prepare yourself... .. .