The Mesh->3D Tets command in the Mesh menu is used to convert a 2D mesh to a 3D mesh of tetrahedron.
This command brings up the Mesh->3D Tets dialog. At the top of the dialog the user selects two data sets that will represent the Top elevation and the Bottom elevation of the 3D mesh. In general the top elevation data set should be completely above the bottom elevation data set. The user also selects how the 3D mesh will be extruded. There are two options: Constant number of layers and Layers distributed by depth. When using Constant number of layers, the user simply enters the number of layers in the edit field. When using the Layers distributed by depth, the user enters a maximum layer thickness for each material present in the 2D mesh in the spread sheet.
The user specifies a top and bottom elevation data set and the 3D mesh is extruded between the two data sets. This process is illustrated in the figures below.
Two surfaces defining the top and bottom of the 3D mesh
Tet mesh extruded between the top and bottom data sets
Two methods are available for determining the number of 3D mesh nodes
to place between the two surfaces: Constant
number of layers and Layers distributed
The first option is a constant number of layers. The figure above was created by specifying 4 layers between the top and bottom surface. In this case five 3D mesh nodes are created between the top and bottom elevation data sets creating 4 layers.
The second option uses the materials assigned to the 2D mesh. The user then specifies a maximum layer thickness for each of the materials. Then as the 3D mesh is extruded the number of nodes will vary depending on the material and the distance between the top and bottom elevation. This is illustrated in the figures below. The first figure show a 2D mesh with 3 materials assigned to it.
2D mesh with 3 materials
A maximum layer thickness was assigned to each of the materials: red- 14.0 ft., blue- 10.0 ft., and green- 6.0 ft. The resulting 3D mesh is shown below.
3D tet mesh created with materials and max layer thickness
Converting 2D Meshes
Creating and Editing 3D Meshes