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[stjern]

This will be a great platform for vehicle simulations no doubt. I have some questions and suggestions.

I think the key is to make a vehicle physics engine that is as general as possible. You can simulate small cars, bikes and huge 18-wheelers with the same parameters. I know because I have done vehicle physics engines myself. In every game I tried to mod there were allways stupid limitations because it was only originally expected to simulate a specific sort of vehicle.

How is the vehicle engine as of now?
Are torque functions used(like LFS) or torque data(like Rfactor)?

I'd say a sort of combinations would be the best, could provide example I have used myself.

I would gladly like to help if I could get the chance. I am a physics student with some programming knowledge and experience of making realistic car games.

[cameni]

The vehicle physics is currently very simple, with wheels approximated with ray casts and a simple force acting on the wheel hubs, lowering linearly with speed.

We plan to implement a better physics, and to expose an interface so that people can implement and experiment with their own. We could use your help indeed - initially we could discuss what would be the requirements on the underlying collision and material system, how to design the interfaces for wheel physics etc.

[ZeosPantera]

Ah, good to see someone with some Physics programming knowledge is now on the forums. You are a welcome edition my friend.

When ever a sim comes out I always post THIS and hope someone is listening..

[stjern]

Ah, good to see someone with some Physics programming knowledge is now on the forums. You are a welcome edition my friend.

When ever a sim comes out I always post THIS and hope someone is listening..

That is some serious realism lol. A little overkill for a general approach maybe... I know you are familiar to Rfactor, I have done alot of modding in Rfactor and find their engine simulation really lame and they still use the same for Rfactor 2 . It doesn't even support boost!

[ZeosPantera]

Ah, but overkill is the most fun and Richard Burns Rally is still considered one of the best simulators of all time.

Plus on Outerra all of the CPU cycles are free for simulation!

[stjern]

Ah, but overkill is the most fun and Richard Burns Rally is still considered one of the best simulators of all time.

Plus on Outerra all of the CPU cycles are free for simulation!

This is how my latest engine simulation goes:

enginedisplacement: 2000      engine size(cc)

RPMTorque=( 0.0, 0.0, 0.0)             (rpm,volumetric efficiency(0-115%), boost(bar/psi),   This defines the volumetric efficiency and boost at this rpm
RPMTorque=( 250.0, 10, 0)
RPMTorque=( 500.0, 20, 0)
RPMTorque=( 750.0, 45, 0)
RPMTorque=( 850.0, 45, 0)
RPMTorque=( 1000.0, 45, 0)
RPMTorque=( 1250.0, 55, 0)
RPMTorque=( 1500.0, 60, 0.2)
RPMTorque=( 1750.0, 65, 0.5)
RPMTorque=( 2000.0, 70, 0.6)
RPMTorque=( 2250.0, 75, 0.6)
RPMTorque=( 2500.0, 78, 0.6)
RPMTorque=( 2750.0, 81, 0.6)
RPMTorque=( 3000.0, 84, 0.6)
RPMTorque=( 3250.0, 86, 0.6)
RPMTorque=( 3500.0, 88, 0.6)
RPMTorque=( 3750.0, 89, 0.6)
RPMTorque=( 4000.0, 89, 0.6)
RPMTorque=( 4250.0, 88, 0.6)
RPMTorque=( 4500.0, 88, 0.6)
RPMTorque=( 4750.0, 87, 0.58)
RPMTorque=( 5000.0, 85, 0.55)
RPMTorque=( 5250.0, 84, 0.52)
RPMTorque=( 5500.0, 81, 0.50)
RPMTorque=( 5750.0, 75, 0.45)    this means at 5750 rpm engine is at 75% VE and has 0.45 bar of boost at full boost.
RPMTorque=( 6000.0, 70, 0.4)
RPMTorque=( 6250.0, 66, 0.4)
RPMTorque=( 6500.0, 60, 0)
RPMTorque=( 6750.0, 50, 0)
RPMTorque=( 7000.0, 35, 0)

boostlag =  x              this is used to simulate the turbo spooling up, to make it more advanced I've made it a function of rpm, but would be even better to define it seperately for every rpm like for boost and volumetric efficiency. Same with gas response.


maxtorque = enginesize / 10 * (volumetric efficiency + boost)           torque(NM)        so at full throttle engine will make (0.88+0.6)*2000/10 = 296 NM of torque at 5500 rpm

compressiontorque ~ enginesize / 100      diffrent numbers used, depends on alot of things hmm     

[ZeosPantera]

Are you working on anything that takes into account the rotational dampening of the transmission/drivetrain/tires and the weight of the components?

I presume this is only "at the crank" performance.

[stjern]

Are you working on anything that takes into account the rotational dampening of the transmission/drivetrain/tires and the weight of the components?

I presume this is only "at the crank" performance.

Yea but so far only the rotational mass of the tires. The rotational mass of the engine is hard to estimate, not many cars have data for how big the flywheel is etc.

Yes ofc it is crank performance. It is not complete tho but simplyfied for easy modding and understanding. To make it more realistic you must also define the compression ratio for every rpm.(and now we asume perfect amount of fuel is injected) You can never be realistic enough hehe.

At perfect volumetric efficiency and compression you could reach over 120nm/litre like in some modern F1 cars.

And the VE figures are in % now so should read 0.xx instead of xx, I was really tired yesterday...

[ZeosPantera]

You know I didn't even think about going into transmissions and how they are handled. Clutch use/slipping and the like..

Oh for your information. Here is the gear lever on a modern Tatra 8x8.



I'm tying to work out in my head how the mechanics of that are handled.

[cameni]

There's a reductor switch on the side of the lever:

[ZeosPantera]

That interior is nicer than most cars..

[stjern]

Tatra T813
displacement = 17640cc     (Diesel V12)

RPMTorque=( 0.0, 0.0, 0.0)             (rpm,volumetric efficiency(0-115%), boost(bar)
RPMTorque=( 250.0, 0, 0)
RPMTorque=( 500.0, 0.25, 0)
RPMTorque=( 750.0, 0.4, 0)
RPMTorque=( 850.0, 0.5, 0)
RPMTorque=( 1000.0, 0.54, 0)
RPMTorque=( 1250.0, 0.56, 0)
RPMTorque=( 1500.0, 0.56, 0)
RPMTorque=( 1750.0, 0.55, 0)
RPMTorque=( 2000.0, 0.54, 0)
RPMTorque=( 2250.0, 0.4, 0)
RPMTorque=( 2500.0, 0.25, 0)

~990 NM of torque at 1300 rpm
~270 hp at 2000 rpm

Nice old engine hehe. Could use some modern turbocharging tho! This thing will be incredibly slow but perfect for offroading.

I'm not sure how much torque a diesel engine gets att full VE, does anyone know? There is this weird myth about diesels having higher torque but I suspect it has slightly less compared to petrol.

[ZeosPantera]

I know diesels have a higher torque simply due to the compression ratio's.. Most times over 20:1. That is why diesel is used for trucks and anything that needs more torque. Also most diesels are turbo charged.

Good Example.

[Fabo.sk]

Nice old engine hehe. Could use some modern turbocharging tho! This thing will be incredibly slow but perfect for offroading.

That is what it is made for. And for towing really heavy stuff (think tank trailer)

[KelvinNZ]

Is the aircraft physics going to parallel the effort put in to the vehicle physics or are you including all vehicles here?