Determines the maximum size of steps or obstacles the player can step
over using the OBB collision detection.
If the player collides with a polygon, the ellipsoid normal at collision point
is evaluated. Collision with the floor results in normal.z == 1, collision at
half the player size in normal.z == 0. For limiting the height the player can
overstep, move_min_z can be set at a minimum z value. By default, move_min_z
== -1, so a player can always glide upwards as long as the step does not exceed
half his height. For overstepping only low steps, set move_min_z at a small
positive value, like 0.4. Please note that the heights to overstep with a certain
value depends on the actual player size.
-1 .. 1 (default: -1)
move_min_z = 0.4;