Half credit will be given for tasks submitted up to 2 days late (zero after that). You will demo your work to me on Monday, February 7.

• bouncing ball
  • use MEL commands to:
    1. create a sphere
    2. add attributes of vx and vy and initialize to reasonable values
  • create an expression that
    1. if it's frame 1, reset the ball to the origin and reinitialize velocity
    2. otherwise update position by adding the velocity to it and add a constant (negative) acceleration to the ball's y velocity
    3. if the ball's y value is less than zero, set it to zero, set velocity to original velocity times scale factor, scale down scale factor
• Spring connected balls - you will interactively move one and the other will move as if attached as a spring
  • use MEL commands
    1. create 2 balls, b1 and b2
    2. to b2, add attributes of velocity in x, y, z
  • create an expression
    1. if it's frame 1, reset b2 to the origin and reinitialize velocity to zero
    2. else
       1. compute the vector between the two balls, d = p1-p2
       2. compute the distance between the two balls, call it 'dist'
       3. get the velocity of b2 into a vector, v
       4. compute the spring force using spring and damper constants, ks and kd

          f = ks*dist*d - kd*v
          

          This will pull b2 right on top of b1. If you want to maintain a separation of 'L', the use

          f = ks*(dist-L)*d - kd*v
          

       5. using the mass of b2, compute the acceleration for b2

          a = f/m
          

       6. add the acceleration to the velocity of b2

          v = v + a
          

       7. add the velocity to the position of b2

          p = p + v
          

  • after setting the current frame to something other than 1, interactively grab b1 and move it around. b2 should follow as if connected by a spring.
  • During your debugging phase, you can re-center b2 by setting the frame to 1.