+/// \param[in] p point
+/// \param[in] l0 starting point of ldir
+/// \param[in] ldir line
+/// \return Vector starting from p perpendicular to ldir
+ERASEABLE
+vector point_line_vec(vector p, vector l0, vector ldir)
+{
+ ldir = normalize(ldir);
+ p = l0 - p;
+ // remove the component in line direction from p
+ return p - ((p * ldir) * ldir);
+}
+