On Wed, 15 Jul 1998, Stefano Fronteddu wrote:
> Hello to all,
Hello!
> I've downloaded F13D Spirit from the net, I've tried to use It with my
> fmsx emulator on PC, but it doesn't work well.
> Starting appare on the screen a lot of orizontal lines, it seems error in
> VDP programming, but it isn't the case.
> Can someone help me, explaining where's the problem ?
Of course it's one more fmsx's bug. I don't want to blame the author,
because I know that the construction of an emulator is something very
hard. But the author says that fmsx emulates an MSX2+, which isn't true.
That's the point: F1 Spirit 3D Special is a MSX2+ game, and use the
hardware resources of the VDP V9958, like horizontal scroll, higher screen
numbers (with more colors), and others. fmsx (last version) doesn't
emulates que hardware horizontal scroll, and this is the bug that you're
seeing.
I wouldn't call this a bug, because this is not really a bug, it's a
non-implementation, but the author shoudn't had said that MSX2+ is
implemented, so we can interpret this as a big bug.
> Thanks to all the replay at my answer about MSX & local network.
F1 Spirit 3D Special uses the horizontal scroll to implement the 3D
steering, this means that when you drives your car to the left or the
right, the lines of the screen are gradually scrolled to the opposite
direction. And the displacement is a function of the line number!
But how is this made? Simply the VDP V9958 has a bit in one of its ports
that indicates the end of each line-tracing, and the program reads this
port frequently. Each time a scan line is finished, a bigger scroll factor
is applied, which makes the next line becomes more displaced. That's a
variable scroll, producing a linear inclination of one range of the image,
which makes the road seems to be curved. At the end of the displaced
region, the scroll register is restored, and the rest of the image stays
unmodified.
If you think in PC VGA programming, you'll see that it's very hard to
emulate this features through software! This explains why there's no
emulator for MSX2+.
BTW, if you want an almost perfect emulation of a MSX1, you should try
BRMSX. BRMSX is available for free at the author's site:
http://www.lsi.usp.br/~ricardo/brmsx.htm
It requires a 486 and a few memory. A Sound Blaster 16 is also
recommended. The emulation of the SCC is not finished, but will be ready
soon.
Bye!
--------------------------------------------------------------
Marco Antonio Simon Dal Poz http://www.lsi.usp.br/~mdalpoz
[EMAIL PROTECTED] "The measure of success is the knowledge"
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