nodal coordinates --
example:
(a) (b) (c)
18 0 0.75 0.50
(a) node # -- global index number of node
(b) gen order -- used to specify a range of nodes; generally just leave it 0 unless
doing something special.
(c) x and y (and z) coordinates -- there are nsd entries; these specify the
physical location of this node in the grid.
End nodal coordinate block with two zeros.
The following figure illustrates the correspondence between node
numbers and physical coordinates for this example:
