Bodies gain extra momentum after bouncing

Question

I am trying to write a simple Physics simulator. However I am facing issues with how the ball bounces. Even though my RESTITUTION is set to 1, the ball bounces a little extra every time it touches the ground.

The Restitution variable:

public static double RESTITUTION=1d;

The code for handling bounce:

if(Y<c.getRadius()){
  VY=Math.abs(VY)*Utils.RESTITUTION;
  Y=c.getRadius();
  c.getCenter().setY(Y);
  c.getV().setY(VY);
  }

All variables use double as data type. Y is the center of the ball. VY is Y-component of velocity.

There's probably some violation of conservation of energy that happens. One way to sort that out is to add an invariant check to correct that with each time step. — duffymo
@duffymo The heat is being taken care of by the fan on the CPU, but the sound must be let out via the loudspeaker. ;-) — laune
Shouldn't you be reversing the sign of the y-component of velocity? What about x-components? I consider it a bad sign that you aren't using a 2D Vector abstraction. — duffymo
Since the code is for handling the ball hitting the ground, I have used Math.abs(), it's just a test. getCenter(), getV() calls return a Vector2D object and I am setting the Y component of the Vector2D by using Vector2D#setY() setter method. — Madeyedexter

laune laune · Accepted Answer · 2016-03-19T12:32:22

If Y < c.getRadius() the ball has already entered the ground by c.getRadius() - Y, and this is added on the way back up.

I think you should keep Y and just invert the speed, etc.

If you bounce at an angle, you might compute the accurate point of impact and correct by that.

Bodies gain extra momentum after bouncing

1 Answers