Raycast vehicle problems

[pHySiQuE]

I have a lot of problems with raycast vehicles hitting my character controllers and "popping" up with a lot of force. This is due to the nature of the character controllers, which are not as exact as regular physics. Is there any way to make the tires ignore certain objects in the raycast? Could it just use the body's OnAABBOverlap function?

[Julio Jerez]

ha yes, the collision filer was had coded. I added that now.

If you sync to github the vehicle has a functionality now

there is a new function
SetContactFilter(CustomControllerConvexCastPreFilter* const filter);

what you do is that after you crate the vehicle to create an objet of type
file \packages\dCustomJoints\CustomControllerManager.h CustomControllerConvexCastPreFilter

and you overload function
CUSTOM_JOINTS_API virtual unsigned Prefilter(const NewtonBody* const body, const NewtonCollision* const myCollision)

there you can check if body or collision shape is one tat you want to collide or skip.
if you want to collide you return 1 other wise you return 0.

you get the information you need from the userdata on the collision or on the body as usual.

if you do no set a collision filter, the engine set the normal one as it was doing before, so it should works.

[Julio Jerez]

the other thing is that, even without a filter that should no happens. when I play the video I see that the tire rise way above the chassis. as if there did not have a upper limit but the do.

did you set the tire pivot too high or the suspension very long? The tire should no move pass the tire hardpoint on eh chassis. BTW I live that old rusty Lincoln continental.

[Julio Jerez]

Ha and I also added the callback for tire friction, which was also had coded to 1.5 in eh demos.

if you set to some low value you can see cool sliding effect like ice surfaces, plus you can also do power slides and drifts.

the function is
dFloat GetTireFrictionCoeficient(const NewtonBody* const body, const NewtonCollision* const myCollision, dLong contacID) const

right now it does not report the collision because I have to add that to the convex cast, or get it from the body. but you get the idea.

is set to 0.5 to show some extreme sliding.

Note: vehicle tire can have fruition coefficient that are larger that 1.0
typical values can be between 1.1 an 1.5 depend on tire pressure. a deflated tire can have a very strong coefficient of friction while a over inflated tire can be veryy slippery

[Julio Jerez]

al right one final change, I made the contact call back filter his own class, this way it can pass more information like what tire is colliding and have the vehicle available, etc

you subclass from

Code: Select all

class CustomVehicleControllerTireCollisionFilter: public CustomControllerConvexCastPreFilter

and you overload functions
virtual unsigned Prefilter(const NewtonBody* const body, const NewtonCollision* const myCollision)

dFloat GetTireFrictionCoefficient (const CustomVehicleControllerBodyStateTire& tire, const NewtonBody* const body, const NewtonCollision* const myCollision, dLong contacID) const


in function Prefilter, you queries the body user data, or myCollision
for use information, and if it matches some object you do not want collision then you return 0
else return 1

function tire GetTireFrictionCoefficient, gives you the which tire is colliding, from that you can get all the information you need to return a coefficient of friction for that tire.

In general you can modulate the friction by the surface the tire is in, and the slip ratio of the tire.
I am simply return 1.0 as default.

a trick to do cool drifting is to make the front tire have more friction than the rear tire.
example you can make front tire 1.2 and rear 1.0
and you get emerging drift form the physics, not fake like almost all game simulation do. it is really amusing.
you need to sync to github.

[pHySiQuE]

I am getting this error whenever I try to use my subclassed object:
IntelliSense: no default constructor exists for class "CustomVehicleControllerTireCollisionFilter"

[Julio Jerez]

I added it now.

[pHySiQuE]

Thanks, here's the result:

[Julio Jerez]

Nice!!
did you play with tire friction?

There are lot of cool tricks you can try. for example for an old Lincoln like the model, they tend to los traction on the rear wheel very eassilly, toy achiv that you just giv eth rear tire a lower frition that the front tires.

The call back for that is in the same filter,
dFloat GetTireFrictionCoefficient (const CustomVehicleControllerBodyStateTire& tire, const NewtonBody* const body, const NewtonCollision* const myCollision, dLong contacID) const

by default returns 1.0

but you can annotate the tires with some value and the you can check what tire it sis that you are getting and the apply the proper friction value.
usually a for tire is aboutt 20% more sticky tha the rear tires.
I will try values like 1.1 for front and 0.9 for rear and play around that vicinity,

[pHySiQuE]

I have been. I think I need to distribute the weight towards the front and lower. My friend had a car like this and it was very very front-heavy. And all cars have their weight in the engine block, to some degree.