Volume 

Menu: Geometry->Create->Contact volume

Contact volumes are defined between two surfaces that are physically in the same place but with different surfaces, lines and points. From a contact volume, it is possible to generate contact elements, to be used by some calculation algorithms, which define special contact between two bodies.

Those equivalent surfaces can be in the same location or can be separated by a movement (separated contact volume). The result will be equal meshes, ensuring a one-to-one relationship between nodes.

Choose 'contact volume' from the menu, and then select the surfaces. GiD automatically searches for possible contacts, combining the selected surfaces in pairs.

Contact elements are, by default, 8-node hexahedra or 6-node prisms (depending on the surface mesh).
However, you can select 2-node lines for all cases (see Element type).

The result elements can be also quadratic.

You can also select no mesh for the contact entity. This makes it possible to have exactly the same mesh for both surfaces but without any additional element between them.
When creating contact volumes, GiD internally checks what surfaces occupy the same location in the space and creates the contact, therefore there is no need to specify what surfaces have to be in contact. For this reason, several surfaces can be selected at once and GiD performs the contact automatically, indicating the number of contact volumes that have been generated.


Geometry Menu>Create>Contact>Separated volume
One feature of GiD is the option to create 'contact separated volumes' for surfaces that are not physically in contact.
For these separated volumes, GiD internally checks whether a unique solid-rigid movement exists between two surfaces and creates the contact. There is the possibility that multiple solid-rigid movements may exist. In this situation, GiD asks for the point image of a source point to define the movement and, consequently, applies the right contact.
Geometry Menu>Create>Contact>Automatic volumes
A tool to automatically create contact volumes between pairs of surfaces (of a selection) on the same location.
If the same contact volume exists it is not created again
Geometry Menu>Create>Geometry from mesh
Menu: Geometry->Create->Geometry from mesh
One node-one point
Creates a geometrical point for each node selected. Layer, material and groups of nodes are preserved in points.
One element-one line
Creates a geometrical line for each line mesh element and points.
Quadratic elements are converted like there were linears, ignoring mid-edge nodes
NURBS patches
This option converts all our mesh model (only surface mesh, triangles and quadrilateral) to a geometry model, obtaining a NURBS surfaces based definition. Creates a group of new layers called "Reconstruction", inside you will see two new layers: the first "All Lines And Points" contains lines and point and the second "Reconstructed Nurbs" the surfaces. If some surface couldn't be reconstructed it will appear a third layer called "SurfMeshes Not Reconstructed" containing the remaining parts converted in Surfmeshes, see more infomation about Surf Mesh.
One element-one surface
Creates a geometrical surface for each surface element (triangles or quadrilaterals) and its boundary curves and points.
Quadratic elements are converted like there were linears, ignoring mid-edge nodes
Nodes->grid surfaces
To create a grid of surfaces from a cloud of 3D nodes. The user will be asked for the cell size
The z of the grid will be extrapolated averaging a collection neighbor nodes
Triangles->grid surfaces
To create a grid of surfaces from a cloud of 3D triangles. The user will be asked for the cell size
The z of the grid will be get from the triangle where the grid corner is projected (in 2D), or from a close node.
Geometry Menu>Create>Object
Menu: Geometry->Create->Object
Toolbar:
With this command it is possible to create the following kinds of objects:

• Rectangle
• Polygon
• Circle
• Sphere
• Cylinder
• Cone
• Prism
• Torus

When creating an object, GiD asks for a center and a normal. To enter the coordinates of the center you can click on the screen or select an existing point (see Point definition ). To enter the normal, GiD displays a window where you can choose one of the three axes or enter the coordinates of a point.

Window to define the direction of the normal to the plane

The In screen button in the Enter normal window lets you manually enter the coordinates of the point which defines the normal: you can directly click on the screen or pick an existing point using the Join option in the Contextual mouse menu.
When using the commands sphere, cylinder, cone, prism or torus, the volume of the object is also created.
Geometry Menu>Create>Old types
Note: These old entities cannot be created from the menus or toolbars. It is still possible, however, to access to this function from the Right buttons.
Geometry Menu>Create>Old types>4-sided surface creation
The 4-sided surface has been substituted by the NURBS surface (see NURBS surface ). This new entity has all the functionality of the old one.
A 4-sided surface is an entity formed by a closed set of four lines in the space. Its mathematical definition is a bilinear Coon's surface. The surface is totally defined by the shape of the lines, with no information about the interior. This means that it will sometimes be necessary to use more surfaces to obtain a good shape definition.
To create a 4-sided surface, several lines must be selected (see Entity selection ). For the creation of a 4-sided surface defined by three lines, it is necessary to divide one of the lines into two pieces (see Divide ). The order of selection is not important, but all of them must join each other by sharing common points and they must form a closed contour. If it cannot be created, information about the endpoints is displayed in a window.
In order to make one or more lines form parts of a polyline (see Polyline ), select the entire polyline as one of the lines and GiD will automatically select the piece or pieces of the polyline that are required. Using this facility, non-conforming surfaces can be created. This means creating a surface by using the entire line on one side of the polyline, and creating more than one 4-sided surface by using parts of it on the other side.
When selecting more than four lines, GiD will automatically search for all the possible 4-sided surfaces that can be created with these lines. This allows the creation of many surfaces at the same time.
The Automatic button is equivalent to automatic 4-sided surface creation (see Automatic 4-sided surface creation ).
If the surfaces lie on the z=0 plane, the orientation of the surfaces will be anti-clockwise in this plane (normal vector points towards z positive). Otherwise, the orientation will be arbitrary. This can be checked with the DrawNormals command (see Normals (only Preprocessing) ).
The Number option lets you choose the label that will be assigned to the next created surface. If a surface with this number already exists, the old line changes its number.
Caution: When creating more than one surface at a time, some undesired surfaces may also be created. It is necessary to check the surfaces after creation and erase the undesired ones.
Geometry Menu>Create>Old types>Automatic 4-sided surface creation
The 4-sided surface has been substituted by the NURBS surface (see NURBS surface). This new entity has all the functionality of the old one.
Inside this option, GiD creates as many 4-sided surfaces as it can find. Every new surface will be created in the current layer.
Caution: When creating more than one surface at a time, some undesired surfaces may also be created. It is necessary to check the surfaces after creation and erase the undesired ones.

Geometry Menu>Create>Old types>Planar surface creation
The planar surface has been substituted by the NURBS surface (see NURBS surface). The latter automatically detects if boundary lines lie in a plane and creates a planar NURBS.
A planar surface is an entity formed by a closed set of lines, all of them lying on the same plane. These lines must share some common endpoints.
To create a planar surface, some lines must be selected (see Entity selection). The order of selection is not important but all of them must join each other by sharing common points and must form a closed contour. If all lines are not in the same plane the surface is not created.
It is possible to add holes to a planar surface. To do so, it is first necessary to create the outside planar surface. After this, press the Hole button and select the created surface. Then select lines that form every hole, one by one. Finish with escape. It is also possible to define the surface and holes at the same time, by selecting all the curves.
If the surfaces lie on the plane z=0, the orientation of the surfaces will be anti-clockwise in this plane (the normal vector points towards z positive). Otherwise, orientation will be arbitrary. This can be checked with the DrawNormals command (see Normals (only Preprocessing)).

NURBS are non-uniform rational B-splines. They are a type of surface that is defined by its control polygon (one set of points that the surface approximates smoothly), one set of knots for the two directions u and v (a non-decreasing list of real numbers between 0 and 1) and, optionally, one set of rational weights.

To draw the isoparametric lines in u,v=0.5, check the surface drawing type option in the preferences window.

• By contour: this creates a NURBS according to its contour lines. GiD automatically calculates the interior information of the surface so as to interpolate the boundaries smoothly. To create a NURBS surface, some lines must be selected (see Entity selection). The order of selection is not important but all of them must join each other by sharing common points and must form a closed contour. The number of lines must be equal to or greater than one and their shape must be topologically similar to a triangle or a quadrilateral in the space if the algorithm is to work correctly. This last argument is not necessary if all the lines lie in one plane. In this case, the surface is created as a trimmed one and any problems with the shape are avoided. It is possible to select the boundary lines and the boundary lines of interior holes at the same time, if all the lines belong to a plane.

Note: The No try planar option (found in the Contextual mouse menu) avoids the creation of a trimmed NURBS surface when lines are coplanar.

Note: To enter rational weights for the surface, use the Edit NURBS surface command (see Edit NURBS).

• Automatic: this automatically creates all possible surfaces with the number of sides given by the user. Every new surface will be created in the current layer.

Caution: When creating more than one surface in one go, it is possible that some undesired surfaces may also be created. It is necessary to check the surfaces after creation and erase the undesired ones.

• Trimmed: this option lets you select one existing NURBS surface and a set of closed lines that are inside the surface. Some of these lines may already belong to the contour of the existing surface. Some other lines may be created with an intersection with another surface. Another new surface will be created without changing the old one. It is possible to select the boundary lines and the boundary lines of interior holes at the same time, if all the lines belong to the surface:

• Untrimmed: this constructs one new surface with the selected surface as its base and with the natural contours of the NURBS surface as its contours. The resulting surface is not trimmed.
• Parallel lines: this lets you create one surface given a set of parallel lines in the space. The new surface will interpolate all the selected lines.
• By points/By line points: these two options are available in the Contextual mouse menu after the NURBS surface creation tool is selected. By points creates a NURBS surface from a cloud of points, and By line points creates a NURBS surface from level curves. These two functions are very useful for creating relief and terrains. In the image below there is a NURBS surface created from level curves:

Note: This surface is an approximation to the selected points/lines, but there is no interpolation.

• Search: this lets you select one line and then creates one surface that contains that line.

Menu: Geometry->Create->Parametric surface
Tool to create a parametric approximated surface