Adding a third vector that pokes out of the plane at an angle allows the entire 2D sheet to slide up and down through space. With three freely varying scalars (av+bw+cu), the span expands from a plane to encompass every conceivable point in the 3D volume, effectively filling all of 3D space.
Conditions: Starting with two linearly independent vectors spanning a plane; Introducing a third vector that is NOT in that plane
Adding a third vector that pokes out of the plane at an angle allows the entire 2D sheet to slide up and down through space. With three freely varying scalars (av+bw+cu), the span expands from a plane to encompass every conceivable point in the 3D volume, effectively filling all of 3D space.
Conditions: Starting with two linearly independent vectors spanning a plane; Introducing a third vector that is NOT in that plane