GiD - The personal pre and post processor

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Menu: Geometry->Edit->SurfMesh
Select one or several surface meshes (see Surface mesh). The options are:

  • Draw mesh: Surface will be drawn as a mesh.
  • No draw mesh: Surface will be drawn as a regular surface with magenta lines close to the boundary lines.


Rebuild surface by boundary
Menu: Geometry->Edit->Rebuild surface by boundary
After selecting some surfaces, each surface will be remplaced by a NURBS surface created by the boundary information.
Note: Selected surfaces are not joined, they will be rebuild independently.
Geometry Menu>Edit>Edit NURBS
Menu: Geometry->Edit->Edit NURBS
Edit NURBS line:
Tool to modify some NURBS geometric properties, like control points, degree, etc.

Edit NURBS line window


Once a NURBS line is selected (use the Pick button in the Edit NURBS Line window), you can edit its control points (see NURBS line). Select the control points as if they were regular points and enter their new positions in the usual way (see Point definition).
The Influence factor affects the movement propagation of the neighboring control points.
Available options:

  • Fix boundary Check the fix boundary option if you do not want to move the boundary control points of the line.
  • Insert knot: You are asked for a knot value between 0.0 and 1.0 and this is then inserted. The program checks that the knot multiplicity is not greater than the order (order=degree+1). As the number of knots increases, the number of control points also increases, so this option can be used to have more points defining the same curve.
  • Knot removal : the inverse of knot insertion. Remove knots if possible without change shape with a given tolerance. (interesting to save memory)
  • Elevate degree: With this option the degree of the curve is raised by one. The new curve will have the same shape but with more control points and knots.
  • Reduce degree : the inverse of degree elevation. Decrease the polynomial degree if possible without change shape with a given tolerance.
  • Change weight: A new positive weight can be introduced for any control point, with the exception of the end points.
  • Cancel weights: All weights of the NURBS are converted to 1.0 and the curve is no longer rational.
  • Reparameterize: With the same control points a new curve is calculated to get a better curve with a more uniform parameterization.
  • Similar cubic: This option converts the curve to a simplified one with degree=3, which is only an approximation of the original one.


Edit NURBS surface:


Once a NURBS surface is selected (use the Pick button of the Edit NURBS Surface window), you can edit its control points intereactively (see NURBS surface). Select the control points as if they were regular points and enter their new positions in the usual way (see Point definition).
Available options:

  • Insert knot: You are asked for a knot value between 0.0 and 1.0 and it is then inserted. The program checks that the knot multiplicity is not greater than the order. This option can be used to have more points defining the same surface.
  • knot removal: the inverse of knot insertion. Remove knots if possible without change shape with a given tolerance. (interesting to save memory)
  • Elevate degree: With this option the degree of the surface is raised by one. The new surface will have the same shape but with more control points and knots.
  • Reduce degree : the inverse of degree elevation. Decrease the polynomial degree if possible without change shape with a given tolerance.
  • Change Weight: A new positive weight can be introduced for any control point, with the exception of the end points that must have weight=1 (to force the surface to pass over the corner control points).
  • Cancel weights: This converts the weights of all the control points to 1.0
  • Reparametrize: This reparameterizes the surface obtaining an optimized surface. When a Nurbs surface is not well parameterized, the mesh is of a lower quality.
  • Similar cubic: This option converts the surface to a simplified one with degree=3 in both parametric directions, which is only an approximation of the original one.


All these options are available in U and V directions.

Control polygon of a NURB surface
The Movement type menu of the Edit NURBS Surface window determines the way the selected knots will move. This movement can be along an axis (X-Axis, Y-Axis, Z-Axis), can describe the Normal of the surface (Normal), can follow the screen movement of the mouse (Screen), or the new location of the knot can be defined by introducing the coordinates of a point (Point).
Note: The Insert knot and Degree elevate options can be chosen for either the u or the v parameter directions.
Geometry Menu>Edit>Convert to NURBS
Menu: Geometry->Edit->Convert to NURBS
This option converts the selected lines or surfaces to NURBS lines or NURBS surfaces.
Note: Some algorithms only work with NURBS entities.

Geometry Menu>Edit>Simplify NURBS
Menu: Geometry->Edit->Simplify NURBS
This option converts the selected NURBS lines or surfaces to other ones very similar to the originals but with a less complicated definition. It can be useful when importing data where a control polygon is too complex for GiD to display or mesh quickly.
The Model option performs the operation over all the geometrical entities in the model.
Geometry Menu>Edit>Hole surface
Menu: Geometry->Edit->Hole surface
To add a hole to a NURBS or planar surface

  • With lines:

With this option you can select one existing NURBS or planar surface and a set of closed lines that are inside it and that form one or more holes. The lines may be created by an intersection with another surface. The holes will be added to the existing surface.

  • With surfaces:

It is possible to define the holes also selecting other existing surfaces, getting its lines to hole the first surface.
The surfaces selected to define holes won't be deleted.


Geometry Menu>Edit>Hole volume
Menu: Geometry->Edit->Hole volume
It is possible to add holes to a volume.
To do so, start by creating the interior volumes as independent volumes. After this, click the Hole button and select the outside volume. Then, select the interior volumes that form every hole, one by one. Finish with escape (see Escape).
It is possible to specify 'NoDeleteHoles' to not delete the volumes used to create the holes (or 'DeleteHoles' to delete them)
Geometry Menu>Edit>Collapse
Menu: Geometry->Edit->Collapse
The Collapse function converts coincident entities, i.e. entities that are very close to each other, into one.
The ImportTolerance variable (see Preferences) determines which entities will be collapsed. Where the distance between two points is less than the tolerance, they will be converted to one. With lines and surfaces, the maximum distance between both entities is calculated and if it is less than ImportTolerance, they are converted to one.
Select the type of entities - point, line, surface or volume - when in geometry mode. All the lower entities that belong to the selected entities will automatically be computed. On pressing escape, the collapse operation will be performed.
The Model option performs the operation over all the geometrical entities in the model.
If the variable 'CollapseAllowMoreTasks' is set to 1 then the collapse do not only collapse entities closer than a tolerance, also do other operations like join lines if are tangent and delete the tangency point.

Geometry Menu>Edit>Uncollapse
Menu: Geometry->Edit->Uncollapse
The Uncollapse function lets you select lines, surfaces or volumes and duplicate all common lower entities.
Typically, if two surfaces share one line as an edge, after applying this function to both surfaces, that line and its shared points will be duplicated and every line will belong to a different surface.
This feature is interesting, for example, if you want to disconnect joined bodies or generate a non-conformal mesh with fewer elements than a conformal one.
Geometry Menu>Edit>Snap to plane
Menu: Geometry->Edit->Snap to plane
This tool modify a little the location of noisy entities, to set an exact 'snap value'.
e.g. to set exactly to z=0.0 the location of entities close to 0.0 (e.g. 1e-6) must set:
snap value to 0.0 (default)
snap axis to Z (default)
snap tolerance a little bigger to 1e-6, e.g. 1e-5 (default is 1e-7)
Geometry Menu>Edit>Intersection
Menu: Geometry->Edit->Intersection
Using this option, the intersection of many geometrical entities can be performed.

  • Lines: This option lets you select several lines for which GiD then tries to find as many intersection points as possible. Lines are divided where applicable.

The 'No Divide Lines' option creates an intersection point but does not modify the lines.

  • Surface-2 points: You need to select one surface and two points that lie approximately over it. GiD calculates the line intersection between the surface and a plane defined by the two given points and the average normal to the surface of these points.

Note: Planar surfaces cannot be used with this option.
Note: See Point in line, Point in surface which can be used to define the points.

  • Surface-lines: You need to select one NURBS surface and several lines. GiD then calculates the intersection between the surface and the lines. Lines will be divided at the intersection point.

The 'No Divide Lines' option creates the intersection point but does not modify the lines.
The Extend/Divide lines option extends the lines until they reach the surface.

  • Surfaces: This command creates the intersection lines between several surfaces.

The 'No Divide Lines' option creates the intersection point but does not split the contour lines.
By default the surfaces are divided, unless the No divide surface option is selected.


Geometry Menu>Edit>Surface boolean operations
Menu: Geometry->Edit->Surface boolean op.
You need to select two 2D surfaces located in the XY plane (order is important when dealing with subtraction).
The valid surface boolean operations are:

  • Union: Fuses two surfaces wherever they intersect to create a single, more complex surface.
  • Intersection: Creates a surface based on the intersecting points of two separate surfaces.
  • Subtraction: Negates a specific portion of a surface to create a hole or indentation.
  • Subtraction and intersection: Creates the intersected and the substracted surface at the same time.




Geometry Menu>Edit>Volume boolean operations
Menu: Geometry->Edit->Volume boolean op.
The GiD Volume Boolean Modeler has been designed to accomplish geometric feats such as physically punching a hole through a volume, combining several volumes into one, and creating a new volume from the intersecting part of several separate volumes.
The valid volume boolean operations are:

  • Union: Fuses several volumes wherever they intersect to create a single, more complex volume.
  • Intersection: Creates a volume based on the intersecting points of several separate volumes.
  • Subtraction: Negates a specific portion of a volume to create a hole or indentation.
  • Subtraction and intersection: Creates the intersected and the substracted volume at the same time.


Note: First the volume where to substract must be selected, then the volumes to be substracted (order is important when dealing with subtraction).

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