Let $G=(S, E)$ be a plane straight-line graph on a finite point set
$S\subset\R^2$ in general position. The incident angles of a vertex $p \in S$
of $G$ are the angles between any two edges of $G$ that appear consecutively in
the circular order of the edges incident to $p$.
A plane straight-line graph is called $\phi$-open if each vertex has an
incident angle of size at least $\phi$. In this paper we study the following
type of question: What is the maximum angle $\phi$ such that for any finite set
$S\subset\R^2$ of points in general position we can find a graph from a certain
class of graphs on $S$ that is $\phi$-open? In particular, we consider the
classes of triangulations, spanning trees, and paths on $S$ and give tight
bounds in most cases.Comment: 15 pages, 14 figures. Apart of minor corrections, some proofs that
were omitted in the previous version are now include