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#ActualEdy

Posted 27 September 2012 - 09:15 AM

I believe that by best contribution to this thread is my article about the pacejka formulas, including the interesting debate at the bottom comments:

Facts and myths on the Pacejka curves

In summary, you need these kind of formulas only when developing high-end ultra-realistic vehicle simulation with real tire sets (think on netKar Pro, rFactor, etc). But you are not required at all to use these approaches for developing realistic vehicle physics. These methods are inherited from the automotive industry and it's quite difficult to implement them properly in video games.

In my tests I was able to develop a very fun and realistic vehicle simulation using basic vector math only, with the vehicle reacting properly to burnouts, drifting, brake locks... everything in a few lines and running at 50 Hz.

Forget those numbers and quantities on Edy's Vehicle Physics. That system was developed as workaround for the bad implementation of the wheel component in PhysX 2.8 (nxWheel, used by Unity as WheelCollider). As one of the nVidia developers confirmed me recently, that implementation was cheap and easily tuned for specific applications. My Vehicle Physics package makes the wheel component behave in a barely acceptable realistic way, but none of its parameters has to do with real vehicle dynamics.

I'm now developing a new tire simulation model designed form scratch specifically for video games. It provides a complete tire simulation that reacts realistically on almost all possible situations of the wheel, including static friction and wheel spin. I expect it to be completed by the end of this year.

About the 1ms deltaT subject: in my opinion the problem with this is that the traditional methods are way too dependent of the deltaT. In a regular implementation of slip ratio, the resulting force exerted by the tire could double if deltaT is doubled. So you could find that your simulation works exactly as expected at a specific deltaT only. This is why I'm developing a method that doesn't depend directly on the deltaT. A small deltaT (< 20ms) helps avoiding instabilities at certain extreme situations, but the resulting force doesn't depend directly on it.

#1Edy

Posted 27 September 2012 - 09:14 AM

I believe that by best contribution to this thread is my article about the pacejka formulas, including the interesting debate at the bottom comments:

Facts and myths on the Pacejka curves

In summary, you need these kind of formulas only when developing high-end ultra-realistic vehicle simulation with real tire sets (think on netKar Pro, rFactor, etc). But you are not required at all to use these approaches for developing realistic vehicle physics. These methods are inherited from the automotive industry and it's quite difficult to implement them properly in video games.

In my tests I was able to develop a very fun and realistic vehicle simulation using basic vector math only, with the vehicle reacting properly to burnouts, drifting, brake locks... everything in a few lines and running at 50 Hz.

Forget those numbers and quantities on Edy's Vehicle Physics. That system was developed as workaround for the bad implementation of the wheel component in PhysX 2.8 (nxWheel, used by Unity as WheelCollider). As one of the nVidia developers confirmed me recently, that implementation was cheap and easily tuned for specific applications. My Vehicle Physics package makes the wheel component behave in a barely acceptable realistic way, but none of its parameters has to do with real vehicle dynamics.

I'm now developing a new tire simulation model designed form scratch specifically for video games. It provides a complete tire simulation that reacts realistically on almost all possible situations of the wheel, including static friction and wheel spin. I expect it to be completed by the end of this year.

About the 1ms deltaT subject: in my opinion the problem with this is that the traditional methods are way too dependent of the deltaT. In a regular implementation of slip ratio, the resulting force exerted by the tire could double if deltaT is doubled. So you could find that your simulation works exactly as expected at a specific deltaT only. This is why I'm developing a method that doesn't depend directly on the deltaT. A small deltaT (< 20ms) helps avoiding instabilities at certain extreme situations, but the resulting force doesn't depend directly on it.

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