The Create Method rollout for the Vector Field space warp lets you specify whether to create the vector field using the cube or box method.
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Create panel > 
(Space Warps) > Particles & Dynamics > Object Type rollout > Vector Field > Create Method rollout
Interface
- cube Forces length, width, and height to be equal.
Creating a cube-shaped space warp is a one-step operation. Starting at the center of the cube, drag in a viewport to set all three dimensions simultaneously. You can change the individual dimensions in the Lattice Parameters rollout.
- box (The default.) Creates a standard box-shaped space warp from one corner to the diagonally opposite corner, with different settings for length, width, and height.