Questions about collision and friction

xYD · January 29, 2024, 2:37pm

I’m a beginner.
My questions are as follows:

If a small ball A collides with objects B and C respectively, how to achieve a collision recovery coefficient of 0.8 when A and B collide and 0.6 when A and C collide?
For example, when ball A collides with stationary B at a speed of 1m/s, the rebound velocity is 0.8m/s, and when ball A collides with stationary C at a speed of 1m/s, the rebound speed is 0.6m/s.
If an object A slides on objects B and C, how can the coefficient of friction be 0.8 when A slides on B and the coefficient of friction be 0.6 when A slides on C?
Which physics engine is better for the above functions? The built-in physics engine or the Bullet or ODE engine?

It would be great if a friend could give a code example.
Thank you!

Max12345 · January 29, 2024, 3:06pm

BMaxV/flipper_game/blob/454ce8390b9441e7d3a7971fe84c70d7b2594347/main.py#L471


      
                  if x in self.bar_ids and ("left bar" in inputs or "right bar" in inputs):
                      d = self.current_ball.position - self.right_bar_WO.pos
                      bar_speed_increase = d.magnitude()/0.4 * math.sin(bar_speed/360)
                                          
                  reflected_movement = reflection(self.current_ball.speed_vector,col_v)
                  m = reflected_movement.magnitude()
                  
                  frac = (bar_speed_increase/m)
                                  
                  self.current_ball.speed_vector = reflected_movement+col_v*bar_speed_increase
                  self.current_ball.speed_vector *= 0.9
                                 
                  # add it to past bounces, so I don't bounce back and
                  # forth in the same spot.
                  # it's not clear how I do rolling and "sling"
                  # acceleration here...
                  self.past_collisions.append(x)
          
          else:
              collisions = {}
          rml=[]

idk how to do the sliding in the panda engine. There might be a collision handler that already does it. I built the stuff myself.

What you get is the fact that things have collided and that’s it. But since you have full information anyway, all the physics calculations can be done by you, any way you want.

xYD · January 31, 2024, 2:52pm

Thank you for your reply.
But I’m not familiar with the whole process of collision, and it seems that it will take me a long time to learn about collision.
Now I’m trying to automate collisions with the ODE engine that comes with the package,
although it doesn’t seem to be working very well.
I’ll try to add my own calculations when I get familiar with it.