object velocity and translation relationship

[bareja]

Hi,

I'm really confused, I have a problem in DOPs. When I try to modify the velocity data, by Motion DOP or Modify Data DOP it doesn't work.

I just wanna setup it to 0 and I can't do this. I've thought that if I setup in Motion DOP, velocity to 0 and operator behavior to "Set Always", object shouldn't move. But it moves! It has strange velocity -0.39.

I've attached simple scene to visualize the problem, and ideas?

Cheers.

setupvelocity.hip

Edited January 21, 2010 by bareja

[graham]

The -0.392266 velocity is the velocity being applied by your gravity force in a single time step (-9.80665 * (1.0 / $FPS)). In DOPs the forces are not applied until the solver step. In this case it starts with 0 velocity but once the simulation starts solving the force velocity is introduced. The object therefor gets solved with the instantaneous contribution of the gravity, but the next time step you are setting the velocity back to 0. The object then gets solved and moved by the gravity force again. This constant setting back to 0 is why you get a slowly moving, constant velocity object.

What is it you are trying to do exactly? If you want the objects to stay still they you can always make them inactive, or only apply gravity to a specific group?

Edited January 21, 2010 by graham

[anim]

or set your velocity Y to compensate for gravity

like -ch("../gravity1/forcey")*$TIMESTEP

it's rather hacky way but can be quite funny since collisions with other objects will have some effect on it