I am working on a physics driven pressable button, but I cannot seem to tackle the minimum and maximum limits.

This is the rig I have set up for the button (as it looks when pressed down).
2D view: 2D view

3D view: 3D view

The idea is that the box collider is a trigger and the button (cylinder, mesh collider) is a rigidbody with configurable joint, locked and limited on a single axis. I am using configurable joint, as that's the only one that supports basic, linear restrictions.

I have set up the configurable joint to restrict motion on a single axis, but the joint only allows single dimensional limit, that is applied to both directions. Screen capture of relevant configuration: Configuration Joint configuration

Basically, the opened Linear Limit section is the last property that has been changed for the joint - anything else are defaults and irrelevant (at least I haven't found my solution in the properties below, mostly angular stuff).

The limit of 0.2 units work, and the button can be pressed - it only gets pressed until those 0.2 units and thats the expected behaviour.
The unexpected is that sometimes the angle at which I hit the button, adds force to the button outwards from the box, and it moves 0.2 away from it, ending up like this:

The unexpected upper limit

Obviously, the specified limit of 0.2 units constrain the movement in both directions from the anchor, actually resulting in the range of -0.2 to 0.2 (relative to anchor).

How, and is it even possible, to restrict the movement only in a single direction relative to anchor?


1 Answer 1


You are correct about the fact that the limit isn't a min-max limit, but rather constraints in both directions. So if your goal is to limit your movement range to 0.2 units, your limit has to be set to 0.1 (-0.1 - 0.1).

For this to work correctly, your initial "button" position has to be centered between the desired min- and max-position.

You can then add an initial force to move the button to its max position or add a Constant Force Component to the button which will push the button outwards. The latter will have the nice effect that the button will move back out once pressed.

  • \$\begingroup\$ Oh, the Constant Force idea is awesome, though, not always desired. Initial force... is it a Configurable Joint property or should I add a script that will hit the button upon Start()? \$\endgroup\$ Dec 31, 2015 at 11:37
  • 1
    \$\begingroup\$ @joltmode It's not a property, you'd have to add a script that moves the button to the desired position in Start. \$\endgroup\$
    – bummzack
    Dec 31, 2015 at 18:05

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