Archive 17/01/2023.

Constraint_point

slapin

Hi, all!

Have anybody tried using point constraint?
It looks like there is some bug - constraint_ field is always NULL
and everything is silently ignored except warning about worldPosition.
All other constraints (hinge, conetwist, slider) do not have this problem.

godan

Yep, I agree that this constraint does not seem to be working properly. I can get the rigid bodies moving, but no constraint interaction at all as far as I can see.

Also, what exactly is this thing supposed to do? My understanding is that, given two rigid bodies and two local frames, this constraints creates a spring between them (thus keeping them a certain distance apart). Is that right? If so, perhaps it should be renamed to Spring or Length constraint?

Mike

It’s Bullet ‘Point to Point’ constraint, hence its name in Urho3D.
It features rotation around the pivots, and no translation.
It works perfectly and can be used for example as a mouse picker, as demonstrated in Bullet demos.

slapin

Well, it probably works in Bullet but definitely doesn’t work in Urho as constraint_ is always NULL.

jmiller

I’m using CONSTRAINT_POINT and it constrains correctly for me. Without it, the body is not constrained. I’m not sure why constraint_ (btTypedConstraint*) is NULL. Maybe someone can clarify.