Re: [Pyode-user] Collision detection works fine in one direction, but not the other

[George <pin...@gm...>]

Well, I think I found the solution. The plane defines a ground-like
object and not a paper-like infinitely thin surface as we're used to
from math. So when the top_rail is used, the simulation assumes the
ball is inside that ground object and goes crazy.

Thanks for your help.

On Mon, Aug 17, 2009 at 8:12 PM, Ian Mallett<geo...@gm...> wrote:
> Hi,
>
> Long answer:
> -Look at the output with raw_input.
> -The code presented seems to make the sphere fall, but then fall the other
> direction, and back and forth until it settles at top_rail.
> -Try setting the gravity to 0, and the ball goes up indefinitely.
> -I recommend moving the two for loops together.  When the rails are removed,
> you see that the sphere just sits there.  An interaction with the rail must
> be starting the sphere moving.  This explains the earlier observation with
> gravity.  It's the top rail, not the bottom rail.
> -The problem only seems to occur when top_rail is over the sphere.  When it
> is at the level of the sphere, the sphere moves up on top of it.  When it is
> a little over the sphere, we see that the sphere is still moving up.
> Intuitively, I flip the normal (and the distance argument).  The result is a
> perfect simulation, even when the gravity is flipped.
>
> Short answer:
> -Change top_rail=ode.GeomPlane(space, (0,1,0), 1.42) to
> top_rail=ode.GeomPlane(space, (0,-1,0), -1.42).
>
> Ian
>
>
>