# As graph matrices?

Let $S_+$ denote the set of semi positive definite matrices in $\mathbb{R}^{2\times 2}$ is known that $S_+\subseteq Sym \simeq\mathbb{R}^{3}$,wherein $Sym$ are the matrices symmetric. But Is it possible to give a geometric interpretation of $S_+$ in $\mathbb{R}^{3}$? Can be graphed?