Ding... the sound of a light bulb going on! This was actually the subject
of many threads when the game first came out, as it was completely
perplexing for a lot of people that the steering lock had to be changed
halfway through the spin. Don't you guys all go play in empty parking lots?
What was also difficult to come to grips with, so to speak, was just how
much momentum those big slicks burn off when they are sliding. Nicely done.
The original NFS1 also captured this peculiar behaviour of cars with big,
grippy tires, but it works much better in NFS:PU. The more you play around,
the more you see some nice things in the model. Foreward and backwards
weight shifts are modelled to a degree, such that you can control your angle
in the air by what you do before a jump. The skids which are laid down seem
to be proportional to the weight on each tire, and have a different
"density" on the road.
Quite fun.
Stephen
"Richard G Clegg" <[email hidden]> wrote in message
news:8mrcqa$qqi$[email hidden]...
some
I was playing Need for Speed Porsche Unleashed the other day in a
break from trying to learn GPL brands hatch and I got to the skid-pad
test on the 911 GT1. One of the things you have to complete is a 360
degree spin in the car. Now I'd got through all the other skid-pad
missions pretty easily in the game so I set off quite confidently.
Could I get the bloody car to spin - could I hell. It was so strange.
The car would get through 180 degrees then the spin would slow and stop
and it was then spinning the other way. It would unspin 180 degrees,
right itself completely and off I'd drive. Happened like this at pretty
much any speed I could get to (slightly different spin if I did
different things with the brake or accelerator). After about 1/2 hour
of trying to spin it I was really cursing the whole game and the physics
model and saying how unrealistic it was. After all, it looked so
strange - like the car had no momentum or the momentum was kind of
reversing or something.
After several dozen half spins it suddenly clicked with me what was
going wrong. When you've done a 180 degree spin, the steering is
totally reversed (because the car is travelling backwards) but in a
light race car with high grip, the front wheels will still be able to grab some
traction. The front wheels started to steer and were correcting the
spin. Changing the lock over at a mid point in the spin enabled the car
to complete a 360 degree spin.
I was pretty amazed I've got to say. It just shows that even a fairly
basic physics model can actually make you understand bits of vehicle
dynamics you hadn't really "got". I'm not sure if a real 911 GT1 would
behave like that (obviously I don't get the chance to spin incredibly
expensive race cars on a regular basis) but the behaviour went from
perplexing "this phyics is terrible" to "wow - I've actually learned
something".
--
Richard G. Clegg Only the mind is waving
Networks and Non-Linear Dynamics Group
Dept. of Mathematics, Uni. of York
UPDATED WWW: http://manor.york.ac.uk/
