Force field shape? (w/ rigid bodies)

What exactly does the “shape” parameter for force fields do? It has an option for “every point” which suggests the force field would be placed at the weighted center of the mesh or something similar, but even with the option selected the force field still acts as a point source, so it’s clearly doing something else (if anything at all).

Also, am I correct in assuming that rigid bodies are treated as point masses in force fields? I made this assumption because I’m can’t observe any rotation that should be there if the bodies were handled as a distributed mass.

I’m running Blender 2.69.

The Shape list changes depending upon what type of object you activate Force Field on. You must have applied it to a mesh to see Every Point. This would imply every point in the mesh is a force field. If you apply a Force Field to an Empty the list is shorter because the Empty has no datablock. A curve gives you another list as well.

If you conduct a simple test, you can see the difference.

The RED cubes are forced away by a single point, the Empty.

The BLUE cubes are forced away by multiple points, the Torus. Each point in the mesh acts as a full power Force Field so I had to turn down the strength by a factor of 100 compared to the other two fields.

The GREEN cubes are forced away by the Curve.

Each field and particle system is on it’s own layer to prevent cross-field contribution.


field_test.blend (555 KB)

Oh, alright, so “point” means vertex. I was getting weird results because it was a very low-poly mesh and it just so happened that the object origin was just next to the closest vertices in my tests.

My thinking was too mathematical. The way I understood it was that a point is an arbitrary location on or inside the mesh, which sounds too advanced even for Blender.

Also, I experimented some more and I think rigid bodies are indeed treated as point masses but soft bodies are treated as 3D masses (probably also based on vertices).

Thanks for your help!