This tutorial will show you how to set limits to the rotation or movement of a joint. This is useful for many purposes, for example to put a door on a hinge that can only swing open and closed at 90 degrees, or for a ragdoll, where you want to constrain the arms and legs to a realistic range of motion.

The first thing we will do is load the example "01 - simple crate.phs". This gives us a quick starting point:

 

Now we select it and use the scale tool to create a flat plank.

 

We press the Hinge button to create a joint. You can see it has appeared underneath the plank, at the center of the scene.

 

Using the move and rotate tools we position the joint next to the plank as shown, so that the plank will swing down in an arc.

 

We use the Change Actor 1 button to assign the plank to the joint.

 

If we run the simulation now the plank will swing freely back and forth. What we shall try to do next is limit it's range of motion to a 90 degree arc.

(Note that I have raised the plank and joint higher so that the plank does not hit the ground) :

 

 

In the joints tab, scroll down untill you find the area shown here, and tick the box "Limits on".

Some light blue planes will appear on the joint, as shown below. The 2 limit planes represent the maximum and minimum rotation of the joint. As they start off at the same position (min and max are set to 0.000), the joint is completely limited - if you run the simulation now, the plank will not move.

Set the min value to -90 degrees. You can see now that the joint will be able to swing only between these 2 limit planes, in a 90 degree arc.

The simulation should now run as shown: