HyperMesh has several functions that are helped by the definition of a volume, such as creating tetrahedral and hexahedral meshes. This can be done either with surfaces that enclose the volume, or with solid geometry entities. Working with solids provides a couple of advantages over surfaces. Selecting the volume for the function requires only a single click because solids represent the volume with a single entity, as opposed to surfaces. Solids that are topologically connected to each other also allow the functions being used to recognize the connection. Creating the mesh in these cases allows the mesh in adjacent volumes to automatically have proper connectivity.
Solid Geometry
HyperMesh supports the same solid geometry that is created in popular CAD software. Solid geometry can be achieved through the importation of native CAD data or can be easily created from bounding surfaces using the Bounding Surfaces subpanel in the Surfaces panel.
Additionally HyperMesh has numerous solid geometry creating tools to assist in the manipulation of solids within the Solids panel. These can be accessed from Geometry > Create > Solids. Click on the various subpanels below (icons at the top of the panel) to get a description of their function.
Solid Editing
The Solid Edit panel is located at Geometry > Edit > Solids and allows you to edit the solids using various methods. Click on the subpanels below (listed on the left side of the panel) to get a description of their function.
Solid Topology
Topology governs the connectivity of solids and thus the connectivity of the elements created from them. Similar to 2D topology, 3D topology is represented by colors as follows:
3D Topology visualization can be controlled using the Visualization Browser 
(visibility of edges and faces based on topology, transparency of surface shading and visibility of fixed points).
