[ODE] Lots of stacked boxes/breaking constraints (was Re: Inside ODE)

[Benny Kramek]

One of my first programs with ode was a brick wall. I succesfully made a 
wall of about 7x7 to run in almost real-time(about 4fps on athlon1200), 
and have a ball roll into it. There were lot's of parameters. The wall 
was built like a real brick wall, interleaved:

  ----  ----  ----
|    ||    ||    |
|    ||    ||    |
  ----  ----  ----
     ----  ----
    |    ||    |
    |    ||    |
     ----  ----
  ----  ----  ----
|    ||    ||    |
|    ||    ||    |
  ----  ----  ----

It was fairly stable. I found out that if the initial setup had the 
bricks just touching, the bricks surrounding it then it was unstable: 
there needed to be tiny cracks between them. If the vertical cracks were 
too large and the wall was too high, then the bricks would fall into 
place, then get squeezed together, and then a shock wave would flow from 
the bottom up to the top totally destroying the wall.