[ODE] Simpler Suspension Geometries

[Billy Zelsnack]

I have my own little physics project (ie, i don't actually use ode), but I
like this list because I am addicted to getting any and all information that
I can about the subject. Good stuff like yesterday when Adam said he
averaged his friction coefficient between two bodies. Same thing that I do,
but I never have actually seen anywhere else. A bit of a a lurker now, but
hoping to be of some use in the future. Does anyone know of a general
purpose physically based modeling list? Anyway. Onto my question.

I just got my pin constraint working (I guess a ball and socket joint in ode
terminology) and what better way to test it out than on the suspension
geometry for a truck. It all works fine, it just seems entirely overkill. I
want to simulate lots of trucks and right now I can pull maybe 4 of them
realtime right now. Each wheel contains the following pieces..

a upper arm
a lower arm
a wheel mount
a wheel
a spring

the upper arm is connected via 2 pins to the body and one pin to the wheel
mount. same for the lower arm.
the wheel is connected via 2 pins to the wheel mount.
the spring connects from the body to the lower arm.

so for each wheel i have 4 rigidbodies and 8 pins
the back wheels are the same, but with an additional pin on each wheelmount
to keep them from steering.

also i have 2 steering bars between the wheel mounts. so two more
rigidbodies and 4 more pins.

for a grand total of

19 rigidbodies
38 pin joints

add in another rigidbody and 2 pins for the tailgate and the grand total
is.....

20 rigidbodies and 40 pins holding them together.

omg. way, way overkill.

i can think of a few ways to build other geometries. for instance, use motor
cycle style suspension for the rear, but still it is complicated.

so.. finally on to the actual question.

What are other people using for simplified geometries? ipion and havok have
special classes just for building cars. That fastcars guy too. What are they
doing? Special fancy joints help out, but the parts still add up quickly.

-billy




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