9.4.1 MSH file format version 1.0

The MSH file format version 1.0 is Gmsh's old native mesh file format, now superseded by the format described in MSH ASCII file format. It is defined as follows:

$NOD
number-of-nodes
node-number x-coord y-coord z-coord
…
$ENDNOD
$ELM
number-of-elements
elm-number elm-type reg-phys reg-elem number-of-nodes node-number-list
…
$ENDELM

where

number-of-nodes

is the number of nodes in the mesh.

node-number

is the number (index) of the n-th node in the mesh; node-number must be a postive (non-zero) integer. Note that the node-numbers do not necessarily have to form a dense nor an ordered sequence.

x-coord y-coord z-coord

are the floating point values giving the X, Y and Z coordinates of the n-th node.

number-of-elements

is the number of elements in the mesh.

elm-number

is the number (index) of the n-th element in the mesh; elm-number must be a postive (non-zero) integer. Note that the elm-numbers do not necessarily have to form a dense nor an ordered sequence.

elm-type

defines the geometrical type of the n-th element:

1

2-node line.

2

3-node triangle.

3

4-node quadrangle.

4

4-node tetrahedron.

5

8-node hexahedron.

6

6-node prism.

7

5-node pyramid.

8

3-node second order line (2 nodes associated with the vertices and 1 with the edge).

9

6-node second order triangle (3 nodes associated with the vertices and 3 with the edges).

10

9-node second order quadrangle (4 nodes associated with the vertices, 4 with the edges and 1 with the face).

11

10-node second order tetrahedron (4 nodes associated with the vertices and 6 with the edges).

12

27-node second order hexahedron (8 nodes associated with the vertices, 12 with the edges, 6 with the faces and 1 with the volume).

13

18-node second order prism (6 nodes associated with the vertices, 9 with the edges and 3 with the quadrangular faces).

14

14-node second order pyramid (5 nodes associated with the vertices, 8 with the edges and 1 with the quadrangular face).

15

1-node point.

16

8-node second order quadrangle (4 nodes associated with the vertices and 4 with the edges).

17

20-node second order hexahedron (8 nodes associated with the vertices and 12 with the edges).

18

15-node second order prism (6 nodes associated with the vertices and 9 with the edges).

19

13-node second order pyramid (5 nodes associated with the vertices and 8 with the edges).

See below for the ordering of the nodes.

reg-phys

is the number of the physical entity to which the element belongs; reg-phys must be a postive integer, or zero. If reg-phys is equal to zero, the element is considered not to belong to any physical entity.

reg-elem

is the number of the elementary entity to which the element belongs; reg-elem must be a postive (non-zero) integer.

number-of-nodes

is the number of nodes for the n-th element. This is redundant, but kept for backward compatibility.

node-number-list

is the list of the number-of-nodes node numbers of the n-th element. The ordering of the nodes is given in Node ordering; for second order elements, the first order nodes are given first, followed by the nodes associated with the edges, followed by the nodes associated with the quadrangular faces (if any), followed by the nodes associated with the volume (if any). The ordering of these additional nodes follows the ordering of the edges and quadrangular faces given in Node ordering.