[ODE] Racing game settings (update)

[Alex Amsel]

On 30 Jul 2004 at 0:42, Jon Watte did put forth to me :

> > When setting slip2 I have the option of using the angular vel of the
> > wheel or the vel of the chassis in the forward direction or the
> > overall vel of the chassis. I was guessing that (even allowing for
> > wheel slip) that I should use the angular vel of the wheel in the
> > axis2 direction, except I'm not sure how to calc linear or angular
> > vel in a particular axis (I mul'ed the vel and normalised axis2 axis
> > but that ain't right).
> 
> I already suggested the following, but it bears repeating:
> 
> Calculate a front vector for the wheel as:
>    fDir1 = normalize( cross( wheelAxis, groundNormal ) )

Sorry you misunderstand - I mean if I scale the slip parameter by the 
velocity.
 
Must admit this is the one bit I'm not happy with really on our 
system yet. I can get it set up to be "ok" but not really to be good 
and fun to drive. As slip/mu vary I can make it better but I've never 
found a particularly good mix for driveability, and certainly not 
managed to get it to do any nice handbrake turn sorta stuff! Maybe 
just my set up, maybe the model won't do it as it is and needs some 
extra work :)

> > The only other real issue I had, and still have, is slight
> > variations in the front wheel direction cause slight steering issues
> > when the wheels should be straight. I did a lot of testing and tried
> > a lot of 
> 
> Real cars don't drive straight. Especially not at the forces 
> and speeds that you'll cram into a typical arcade game. If you 
> want smoother, more game-like physics, I recommend the box 
> with four ray casts.

Yes I realise this. Its a very small error but it is noticeable. It 
increases to 0.01 whoile normally at 0.0001 or smaller. Improves 
accuracy with smaller stepsize of course.
 
> > a preset target vel and throttle-linked torque) is the problem. It
> > is less apparent with foot off the gas. Ideas?
> 
> Smaller CFM, higher ERP. Try 1e-5 and 1-1e-4 respectively 
> if you're using floats. Or switch to doubles, and use something 
> like 1e-8 and 1-1e-8.

Doubles aren't an option (tho I'm sure they'd sort it). Toyed with 
those kind of cfm/erp values too.
 
> You can set the SoftCFM and SoftERP flags and specify the 
> CFM/ERP only for these joints, if you don't want to make 
> your entire system ultra-stiff.

Added some nasty artifacts to the system, tho I'll play around a bit 
more.

Alex Amsel 
Tuna Technologies Ltd (Sheffield, UK)
PC/Console Game Development
Tel: +44 (0)114 266 2211  Mob: +44(0)7771 524 632