what AntonSynytsia say is right, but he is forgetting one part.
the body has unlimited capacity to push other body around.
this is what justify the existence of kinematic body, they are static bodies with mass.
this has to do with conservation for momentum
when two rigid body collide at the moment of collision the total momentum before collision should be equal to the total momentum after collision plus the loses during collision.
This principle is broken when we make the idealizing of a static rigid body.
a static rigid body is one in which has infinity mass.
this makes that when a dynamics body collide with a static body, the momentum that is distributed to the static body is lost because an infinity mass (wich is just a large number) multiplies by zero (the velocity) is always zero therefore the amount of momentum of a static before and after collision is zero, simple because its velocity is zero.
Now imagine a static body with a non zero velocity, its momentum is nearly infinite in computer terms, so this body is relentless in its motion and can push around any obstacle with sale mass. this why AntonSynytsia see then penetrating any other body.
you can try the experiment with this static collision calculator.
http://www.convertalot.com/elastic_coll ... lator.htmltry making the mass of one body as big as you can, you will see that as long as it velocity is zero, it
acts just like in newton, but the moment you set its velocity to non zero, then the other body start receiving unreality values of velocities.
To remedy this problem of moving a static body around and not having it acting unrealistic, I added the kinematic body, which is a static body with mass. now this body act as dynamics body when colliding but they behave like static body in the scene in the sense that the do not get integrated.
This could has been an option on the body but as time progressed I realized that kinematic bodies has some other properties, like they occupy a special location on the body graph and other that I do not remember now, but their application goes beyond just been a flag on the body.
in conclusion AntonSynytsia observations are correct, in the sense if he reset the velocity each time plus he has to integrate then himself, but this is precisely what kinematic are designed to at a much lower cost. it is just better to integrate the kinematic body manually.
there is a game that uses Newton called ship simulator, is a very big mesh that moves around with a special dedicate simulator, but is has bodies on top, this motion is a big problem.
by making the ship does no has infinity mass an being kinematic make possible, the objects in them do not get unreality pushes.
The idealization of rigid body does not support the concept of infinity mass body, because such thing does not really exist in nature, my solution to represent that is the kinematic body.