Real-Time Physics Simulation Forum

Hi,

I was trying to get a realistic tank/crawler type vehicle done with Bullet. However, I failed with normal movements by forces/torque. The crawler was sliding and moving unrealistic.

So I tried with the vehicle physics, my idea was to use e.g. 6 (invisible) wheels and to drive them. However, I discovered to my surprise, that it seems you can only give force to the chassie and the wheels will follow and rotate accordingly. They way vice versa seems much more logical to me (meaning to have "motors/engines" for each wheel, and let the chassie follow (I think thats the way ODE handles this?)).

So now my Qs:

- does anyone have an idea how to make a realistic tank movement?

- will Bullet also support "driven" wheels?

Best regards,
Carsten

Basicalty there are two types of vehicle simulation in Bullet: raycast wheeled vehicles and constraint hinge wheeled vehicles.

Have you looked into hinged wheel vehicle Blender demo? That is the closest to what you want: you can apply torque to the wheels, and that drives the chassis. However, it doesn't have suspension at the moment.

It requires some extra work to get such simulation working properly. It is on my list to make a sample for this in Bullet, for a Fork Lift.

Thanks,
Erwin

calli wrote:Hi,

I was trying to get a realistic tank/crawler type vehicle done with Bullet. However, I failed with normal movements by forces/torque. The crawler was sliding and moving unrealistic.

So I tried with the vehicle physics, my idea was to use e.g. 6 (invisible) wheels and to drive them. However, I discovered to my surprise, that it seems you can only give force to the chassie and the wheels will follow and rotate accordingly. They way vice versa seems much more logical to me (meaning to have "motors/engines" for each wheel, and let the chassie follow (I think thats the way ODE handles this?)).

So now my Qs:

- does anyone have an idea how to make a realistic tank movement?

- will Bullet also support "driven" wheels?

Best regards,
Carsten

Erwin Coumans wrote: Have you looked into hinged wheel vehicle Blender demo? That is the closest to what you want: you can apply torque to the wheels, and that drives the chassis. However, it doesn't have suspension at the moment.

Ah, really.... I missed that hinged wheel demo!

I now have some nice crawler movement on a plane, however, without suspension its hard to drive on uneven terrain...

It would also be nice to have some friction on the hinges.

Carsten

After tweaking and some magic, I got a nice crawler even with a working bucket for driving spheres around.

Too bad I have to tweak some more because I had "Enable all frames" on and now without it works not so good without that option.



It's allready fun to move things, even if it needs more tweaking



Nice, spheres are rolling



No sliding sideways.

Carsten

That looks very cool! Can you mail the .blend to blender at erwincoumans.com ?

Too bad I have to tweak some more because I had "Enable all frames" on and now without it works not so good without that option.

This 'enable all frames' problem will be fixed soon. Bullet is now framerate independent, but this isn't integrated into Blender yet.

Please stay tuned
Erwin

I second that motion! This looks really neat!

looks like the basis for a cool game

Hi, I'm just getting into this blender physics thing.

The problem I would like to model uses a bucket to transport grain particles. Hence I was thinking your dozer was a close approximation. Is there any chance I could have a look at your model/file??

If you're building a product then no problems, I'll keep trying other sample files.

Have a nice day,
Tray

My "hack" is not working anymore, I had not the time to look into it. I even can`t tell whats wrong....

I guess I need to rebuild all from scratch to get it working again.

Carsten

Those screens look really cool. What about a Bob the Builder game.

Yeh, looks a bit like bob the builder!

Looks pretty good though, could be the basis for a simple game.