I have a NURBS surface and I have made it a passive a rigid body. Then I had a sphere with a gravity field to it. But as soon as I play the animation, the sphere simply simply sticks to the NURBS surface and I have a error like this "rigid body interpenetration occured between 'ball' and 'path'." Ball is my sphere and 'path' is my NURBS surface. Maya help hinted me to correct my normals. How do I do that ? Please help me.
There is a 'Reverse Surface' command in the Edit NURBS menu. You can reverse along U or V (don't do both as this will reverse it twice, leaving the normals pointing in the same direction they were originally).
To check the normal direction, use the Display > NURBS display > Surface Normals command. The lines sticking out from your surface should point up (assuming the ball is falling from above).
A quick test could also be done just by rotating your surface 180 degrees so it's upside down, and see if that makes a difference.