p2 detect collision from one side

[1ipt0n]

Hi,
Im trying to detect collision in p2 from one side (like jumping on top of something) its easy with arcade phisics, but p2 don't have such option, i think.
 
So is there any way to implement this?
 
if not than I was thinking about sticking another invisible body to a side of object and detect collision with that second object instead.
But I dont know how to stick other object to first one and I've experimented with RevoluteConstraint to do it but it;s not what I intended.
 
my code:

var constraint = game.physics.p2.createRevoluteConstraint(arrow, [20, 5.5 ], arrowTop, [5.5,5.5]);    constraint.collideConnected=false;    constraint.setStiffness(600);    constraint.update();

but it behave like two objects on elastic  rope so sometimes  arrowTop if closer to arrow and sometimes its further . even if I set more stiffness it's bouncing.
Is there way to stick two bodies like on glue instead of rope ?

[icp]

https://schteppe.github.io/p2.js/demos/lock.html

 

Use game.physics.p2.LockConstraint .

[1ipt0n]

This is great, thank You icp !