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1994-02-02
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Frequently asked Questions (or at least some I've made up)
QUESTION AND ANSWERS:
Q. Some of my old scripts don't work.
A. the problem could be
1. you have an object named spacer, this is now a built in
object so you can replace your spacer with a more standard
one, e.g. spacer 0.5.
2. the picture doesn't look the same because SCALE now works
in a more sensible fashion, sorry but that's progress.
I promise I will try to avoid redefining implementations
like that, but SCALE was pretty bad.
Q. It's awfully slow. Can I make it go faster?
A. Try a lower screen res (e.g. -res1),
Try turning off the bios switch, (-bios-),
(or try -modex if you can't use -bios-)
For -res2 or higher try using an EMS driver, this can be a lot faster.
Try using spheres or boxes instead of ellipses, and ellipses
instead of toroids until you have a final form ready.
Don't bother with wireframe, or falt views, they're not much faster.
I have written as much of the display code in integers as I can,
if it's still slow there is probably not much I can do, I
developed this program on a 25Mhz 386 without a co-processor, and
tested it on a 16Mhz 386sx with a co-pro so there shouldn't be
too many people for whom this program is way too slow.
Q. The display doesn't look right, the edges are not straight,
the spheres aren't round, etc. etc.
A. Try using -q and a number from 0 to 5, the spheres will be better,
but oh so slow. As for the crumbly edges where things intersect, YUP,
they're pretty bad aren't they! I am working on this. It's something
to do with using integer bresenham algorithms throughout the
drawing phase.
Oh and finally if you want perfection then use form to produce POV
output (flags -pov+ -display-) and raytrace it (see you next week
sometime). For a familiar output picture use the POV flag -q3 and
quickvue.pov.
-- NEWSFLASH
as of 10th November there is now a new -float+ flag.
This fixes the crumbly edges but at the expense of speed (4-10
times slower), unless you have a 486 in which case you'll
probably not notice (lucky swine). There may still be some
crumbliness due to the fact that I'm using an integer zbuffer, if
you don't like it use POV!
-- NEWSFLASH
as of FORM version 3 the integer display routines
have been improved, they're definitely not perfect, but they are better.
Q. FORM crashes when running under windows or QEMM with STEALTH,
just as it is about to start displaying. Why?
A. The display detection code seems to give Windows 3.1 (tm etc.)
and QEMM (tm etc.) severe heartburn. This problem made me decide to
use a VESA driver. If I install my VESA driver before windows (I use
UNIVESA) then I have no problems. Again if I tried to install UNIVESA
after running up windows it had the same effect, (no coincidence as
the code I use is from the same author).
Perhaps you could also try extra stealth exclusions if you're
using QEMM.
Q. I haven't got a VESA driver for my card, what can I do?
A. If you don't have one don't worry, FORM will use it's inbuilt
video routines, the only problem you may find is if you are
running under windows. I suggest that you try and get hold of
UNIVESA, it's the one I use, and it's free, and it's recomended
by the POV team.
Q. My VESA driver kills windows so I don't like using it.
A. I have actually come across this problem, try using UNIVESA. See
previous question.
Q. My machine can support a resolution of 1024x768 at 256 colours
but form won't display at a res higher than 800x600.
A. You almost certainly don't have enough extended/expanded memory
for the ZBuffer workspace. You need twice as much extended memory
free as there are pixels, ie for 1024x768 you need 2*768K bytes
or around 1.4Meg of extended/expanded memory.
You can try using the -disk+ flag, this will allow FORM to use
diskspace as ZBUFFER. There is a file cache built in, but it only
uses conventional memory. If you finc the program is too slow,
try loading an external disk cache.
Alternative Trick: Try running windows with a permanent swap
file, shell out to DOS using a PIF file with the EMS settings set
to -1 (allow as much as possible) and try again. (Dont forget to
load a VESA driver if need be). Windows will provide you with
some virtual EMS!
Q. How can I input Textures, I hate having to edit the POV file each time.
A. This restriction is being lifted even as you read this doc. You CAN
now enter textures, it's a little crude at the moment (10th Nov 93)
but it does work, requires POV version 2.
Q. I've got this brilliant ray tracer called "Wait All Day", can I
produce output for it?
A. If you send me enough information about the input file format
I'll see what I can do. See FEEDBACK at the top of this doc.
Q. Are you going to add colour?
A. I may add some colour for true colour monitors. I'll have to complete
textures first. This is looking more and more likely, now.
Q. It's great, where can I get a version that works?
A. What do you mean it doesn't work! Email some bugs to me, better
yet Email some praise to me and I'll let you know where you can
get the latest version.
rummy@snaffle.demon.co.uk
Andrew Rowbottom