Wheel softness effect

[PJani]

Hey i am working on multibodyvehicle wheels and i am trying to create something like as in my sketch which will simulate "constant" contact with the ground?

Any idea where to start?

[Carli]

Raycasting could help

[PJani]

I would like to avoid raycast, because i need to have this effect on edges slopes or uneven terrain. ;P

[JernejL]

i think what you want is soft body physics.. but that's not yet in newton, however you can simulate a tire continously in contact with convex casting..

[PJani]

i think what you want is soft body physics.. but that's not yet in newton, however you can simulate a tire continously in contact with convex casting..

convex casting is the thing i am looking for thank you.

edit: soft body physics would be overkill ;P

[PJani]

am only one question how could i create fake contact?

[Julio Jerez]

That's a good question? I never did that,

you could just find the contact joints form teh callback and manipulate the contacts.

[PJani]

Hmm what if i want to make this?

is there any good way to make partial penetration of ground?

[Julio Jerez]

The only think I can think of is allowwing
void NewtonMaterialSetSurfaceThickness (const NewtonWorld* newtonWorld, int id0, int id1, dFloat thickness);

to take a negative value for thickness. that way the bodey will collide at soem penetartion depth.
I cannot say now, but I believe thickness is clamped to zero which is the default.
a positive value will collide similar to copmercial engine whe the requiere a skin thickness for collision to work properlly.
I will have to find out is is possible to allow thickness to be negative.

onothet solution would be using a collision shape smaller tha the visual mesh.
I have not follow this, but whey cannot you just make the shape smaller?
I am guessing you want a perpetual contact, which I think a negative thnickeness will guarantee.

another way will be to make a ContactCustomJoint, that is updated before the update I think with the collision system.
I think.

[PJani]

I will look that thickness.

onothet solution would be using a collision shape smaller tha the visual mesh.
I have not follow this, but whey cannot you just make the shape smaller?
I am guessing you want a perpetual contact, which I think a negative thnickeness will guarantee.

If i would like to make wheels visually "soft" i would do as you suggested jep i am looking for perpetual(i couldn't get that word in my head) contact, because wheels doesnt have real friction(i am thinking because they are loosing contact which doesnt happen on real tires).

Edit: Jep it seems that is clamped to 0.0 :S.

[PJani]

It is possible to un clamp it?

[Julio Jerez]

I do not know, but I i will check it out, I beleive ther shoul be no problem.
did you try setting thickness to a negetive value and read it back?

It can not be left unclamped because if is is too large then it may even be bigget that the shape with.

[PJani]

The problem is i dont know how to readit back. I just did set it to negative value -0.5f (in my units half a meter). And i didnt see any penetration so that why i assuming that is clamped to 0.0