Free realization space

True when the stored realization space chart has defining ideal $(0)$: there are no equations, only inequations, so the space is an open subset of affine space (or of a torus) over $\mathbb Z$. Rigid matroids whose one-point space over $\mathbb Z$ has no equations are counted as free too.

For free matroids the affine diagram is an actual realization over $\mathbb R$. Free spaces also count as principal.