rec.autos.simulators

by **Dave Pollatse** » Tue, 04 Mar 2003 15:21:46

heh heh, actually I often convert back to english units for debugging
outputs--those damned English colonialists condemned us Americans to a
screwed up measuring system--perhaps if Napoleon had taken over America for
a few years, converted us to metric, and then left... ;)

For some reason I can think in meters and meters/second^x, but I have a real
hard time visualizing things like spring constants and torque in SI units...
maybe my little brain can only hold one "unit" constant at a time, so
converting from meters to feet or km to miles requires only one mental
multiply or divide, while converting N/m to lbs/in requires two...

> On Sun, 02 Mar 2003 00:43:19 GMT, "Dave Pollatsek"

> >Models in 3DSMAX are done in inches, and with the cars tipped on their
ends
> >for some reason, so I think +z is forward and +x is left. The 3DS
exporter
> >for the pitcrew used meters, though. Tracks in Multigen are in meters,
and
> >Y is up. Our game's graphics system uses meters, with +x = left, +y =
up.
> >Our internal matrix routines use left-handed notation: x' = x M and
> >left-handed cross products, but my new physics stuff uses my pseudo-C to
VU
> >compiler using the more standard linear algebra notation.
> ...

> Enough perhaps at times to get you in a straightjacket if you don't go
> out once in a while. ;-)

> >pounds-per-inch, etc.), and converted to metric at load time for internal
> >computations, which are all in SI units.

> So I guess you do all your debugging output in SI units?

> >but I do remember the one
> >time we had 20,000 lb AI cars briefly (someone thought the mass was in
> >Newtons or something), that were just sort of bobbing up and down at the
> >start finish line

> Well, you can call that a 'feature', I'd say. :) Call it 'Old American
> Cars Heat' and you're set...

> Ruud van Gaal
> Free car sim: http://www.racesimcentral.net/
> Pencil art : http://www.racesimcentral.net/

by **Ruud van Ga** » Tue, 04 Mar 2003 19:04:09

On Mon, 03 Mar 2003 06:21:46 GMT, "Dave Pollatsek"

>heh heh, actually I often convert back to english units for debugging
>outputs--those damned English colonialists condemned us Americans to a
>screwed up measuring system--perhaps if Napoleon had taken over America for
>a few years, converted us to metric, and then left... ;)

Yep, that would save quite a couple of funny constants (5151?) that
could be used for other more fun stuff, like remembering the year that
Napoleon had left. ;-)
Besides, combinations like 'slug' and 'Ferrari' don't really seem to
have the same feel about them. It just doesn't sound high-tech
anymore. ;-) Hail SI.

That's ok I guess; I have a hard time visualizing what N/m does
anyway, lol. Although I do think the 5N/m of steering torque I felt
was actually that, 5N/m. It felt like 10N/m was enough to rip your
hand off. That does give you a clue. :)

It's just at one time you can draw a meter length line on the floor,
and be off by only a couple of centimeters. That helps visualizing
things indeed.

Ruud van Gaal
Free car sim: http://www.racer.nl/
Pencil art : http://www.marketgraph.nl/gallery/

by **Stephen Clibber** » Wed, 05 Mar 2003 06:46:54

Ironically, us english have pretty much gone metric now, it's just you lot
over the pond who stick with those bizarre old units...
I mean, really, Slugs and Stones and Feet... It sounds like some kind of
weird torture device... ;)

by **Dave Pollatse** » Thu, 06 Mar 2003 10:41:31

hey man, you guys are the ones who use "stones" in common parlance for
measuring human weight... I think slugs are only used over here by
engineers, and cubits are *so* last millenium... ;)

I remember we thought we were so "l33t" when we made Viper Racing ask
Windows if we should display metric or english units (along with numeric
seperator, date format, etc), and have all the in-game displays convert
automatically. Then an English user complained that the speeds were shown
in KPH on his machine. (At the time, at least, Windows didn't have any
setting for "screwed up country that can't decide if they're metric or
english" and just returned "metric" for UK)

oops.

Oh, and just to stay vaguely on topic, I just got a copy of Pacejka's new
book, "Tire and Vehicle Dynamics" (I think at most an hour elapsed between
when I got the postcard from SAE announcing it and when I ordered it from
their website!). Looks promising so far, and it's nice to read an actual
book instead of another .PDF file for a change...

> Ironically, us english have pretty much gone metric now, it's just you
lot
> over the pond who stick with those bizarre old units...
> I mean, really, Slugs and Stones and Feet... It sounds like some kind of
> weird torture device... ;)

by **Ruud van Ga** » Thu, 06 Mar 2003 21:33:10

On Wed, 05 Mar 2003 01:41:31 GMT, "Dave Pollatsek"

>I remember we thought we were so "l33t" when we made Viper Racing ask
>Windows if we should display metric or english units (along with numeric
>seperator, date format, etc), and have all the in-game displays convert
>automatically. Then an English user complained that the speeds were shown
>in KPH on his machine. (At the time, at least, Windows didn't have any
>setting for "screwed up country that can't decide if they're metric or
>english" and just returned "metric" for UK)

Ouch, just like I saw a language (it wasn't VB was it?) that started
to convert it source code; so instead of 'IF A=5 THEN' you got (in
Dutch) 'ALS A=5 DAN'. Yeah, that's really handy! Even worse, the , and
. notation got confusing when a script was used on another machine, as
writing 5.3 would be recognized by one machine, and not the other (if
languages differ).

It's quite ***, it starts out immediately with raw stuff; might
be interesting indeed. A nice note about the book; it should have come
out a bit sooner than this, but in fact the first (unreleased) edition
came out with the title 'Tyre Dynamics and Vehicle Mechanics' (I've
seen a copy), which wasn't quite what is was supposed to be. :) So it
got delayed a bit.

Ruud van Gaal
Free car sim: http://www.racesimcentral.net/
Pencil art : http://www.racesimcentral.net/

by **Stephen Clibber** » Fri, 07 Mar 2003 05:36:32

D'oh! That's actually a very fair point... :)
I've just been writing a unit converter for my sim which reads string
descriptions of units, converts them to SI for use in the engine, and also
checks that they are dimensionally appropriate for the quantity being set.
May be overkill really, but it's quite nice to be able to specify (for
example) tyre pressures in psi or kPa or atmospheres or whatever in files
and editors.

I've got that too; I'm only on chapter 3 or so, but it's already
considerably deepened my understanding of tyre modelling, and given me quite
a few ideas for the future. Good stuff!

rec.autos.simulators

Car physics: Pacejka camber signs?

Car physics: Pacejka camber signs?

Car physics: Pacejka camber signs?

Car physics: Pacejka camber signs?

Car physics: Pacejka camber signs?

Car physics: Pacejka camber signs?

Car physics: Pacejka camber signs?