Fast Image Routine & Saving a sequence
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Faster Image Routines
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I have just seen the XP3 image routines and noticed that they could
be a lot faster, i will start off with the VGA memory addressing.
The VGA memory is 64000 bytes big, it's NOT 320*200. Remember that
you needn't have to locate a pixel on screen by x & y positions,
unless you really want to!! And if you do, do not calculate your pos
in memory with (y*200), but make a look-up table. You should always
make a look-up table in graphic-mode. Doing stuff like * and / takes
more time from the CPU then using an Euphoria Pixel routine.
Better not use sequences, but allocate memory space and copy pieces
of memory to the VGA memory.
If you want to copy more than one entire row, poke it all in once
instead of poking row by row. However the you must poke an entire
row, cause after the place where the row ends the new one should
start!
Why does 0 or 6 return 1 instead of 6 ?? and does anyone know why
you can't use XOR on sequences??? It would be helpfull for sprites,
the best idea would be to have mem_copy functions with OR, XOR, NOT &
AND. And to have the ability to skip a number of bytes each 320 or
200 or any other specified value with a mem_copy command, (If anyone
at RDS woud be so nice to include it in a new version, ask me for
details about the suggestion to skip a number of values, i'll then
explain it better.)
If you use sprites, you must copy each horizontal line seperately,
if you do so (and you must for sprites) you should start each line
where the first not see-through pixel is. You can store these values
in a look-up table(sequence!) . And offcourse you must end where the
last not see-through pixel is, this speeds sprites with a lot of
see-through pixels on the side up a lot! Also mark for each sprite if
it has any see-through pixels NOT on a side. Cause if all the pixels
are on the side, you needn't have to check for see-through pixels.
Balls in pinball games could be draw a lot quicker that way, starting
each horizontal line where the real image begins and ending each
horizontal line where the real picture ends.
The above sprite method is not usefull when your sprite is as width
as the screen, if it is you should copy all the horizontal lines in
once instead of each line seperately.
You can also use sequences, then you must have a virtual screen
with the background data and a virtual screen with the foreground
data, each of the SAME size. Don't use a 2-dimensioned sequence, but
use one long sequence, cause it uses less memory, and can be poked
very quickly to the screen in once . (Only if the virtual screens
have the sane width as the real screen!)
The only comment on the XP3 source is that they poke each line
seperately which they needn't, they can poke it all in once!!
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Saving a sequence to disk
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The XP3 source also allows you to load & save multiple pictures to
disk, that's handy but very restrictive. I'll write a routine which
save an Euphoria sequence to disk with LZH Compression maintaining
it's orgininal structure. That kind of routine can be used for a much
more purposes. I will be using the same technique as i used in EDM.E
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BTW This mail maight look really negative about your routines(XP3),
but i'm not. I have much more inspiration now thanks to your
routines, and your alpha version of your game looks really nice,
still i would change the code the poke virtual screens (like the ones
you use) in once, not row by row! And i really appriciate people
sharing code like this, take for example lord generic production
which problely has really nice routines, but they aren't available
unless you pay them money. I know that they earn the money and they
problely need it too, but it's unfair to all the people (including
you) who do give their techniques away for free. He uses the font
library and sound blaster routines, but do they get any of the money
he earns with it?? I do not know, but i am curious, if not it would
be so unfair!! (Since they do got to pay for his routines!!)
I know, it was too long, i should be ashamed and your problely
didn't read it all too, well that's your problem isn't it??
BTW How many dutch people are on this ??
(I know about 2)
Ralf Nieuwenhuijsen
nieuwen at xs4all.nl
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