GiD - The personal pre and post processor

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These are the GiD editing options for geometrical entities:
Geometry Menu>Edit>Move point
Menu: Geometry->Edit->Move point
By using this command, an existing point is selected and moved. The new position is entered in the usual way (see Point definition). If the new position is an existing point (when using join), GiD will determine the distance between the points and ask if they should be joined. If the answer is yes, both points are converted into one. Any lines of surfaces that include the point in question will be moved accordingly in order that any links are maintained; this may lead to these lines or surfaces being distorted.
Geometry Menu>Edit>Divide
Menu: Geometry->Edit->Divide
The Divide command can be applied either to lines, polylines , surfaces (including trimmed surfaces), and volumes.

  • Polylines: In the case of polylines, an existing interior point must be chosen. The polyline will be converted into two lines that may or may not be polylines.


Polyline division has the option Angle which allows you to divide the polyline at all the points where the angle between the sub-lines is greater than a given value.
Caution: An interior point must belong to the first level of a polyline (see Polyline).
In the case of lines and surfaces, once the entity has been selected the division can be done in several ways:

  • Num divisions: The line or surface will be converted into equally spaced pieces. In the case of surfaces it is necessary to give the division direction as u or v.
  • Near point: With this option one point must be selected near the line or the surface. Points inside the entities can be selected (see Point in line, or Point in surface). The line or the surface will be divided into two entities near that point. In the case of surfaces it is necessary to give the division direction as u or v.
  • Parameter: One factor is given between 0.0 and 1.0 and the entity will be divided where the parametric variable takes that value. In the case of surfaces it is necessary to give the division direction as u or v.
  • Relative length: (lines only) One factor is given between 0.0 and 1.0 to divide the line with relative arc length ratio equal to the selected factor. (Same concept as Parameter if the curve was arc length parameterized).
  • Length: (lines only) The length of the resulting divided lines is given, and GiD divides the line into as many lines as it can. If the length given is bigger than the length of the selected line, no division is made.


  • Split: (surfaces or volumes) The surface/volume will be divided following the divide lines/surfaces. These lines/surfaces must share points/lines with the to be splitted (Command: Geometry Edit SplitSurf/SplitVolume ).


Note: After the division, the old entity disappears and the new entities are created.
Geometry Menu>Edit>Join
Menu: Geometry->Edit->Join
With this option you try to join connected entities.
Join lines:
To join the lines of a selection that are connected with 'similar tangent' (with an user tolerance).
Note: the lines are not joined if the connection point belongs to other lines, has some condition applied, or the lines have set an structured number of divisions.
Join surfaces:

  • Rebuild by boundary:

A group or connected surfaces must be selected in order to try to create a single approximated surface.

    • QuickJoin (default option)
    • NoQuickJoin. More parameters are available.
      • IsProjectable : Yes or Not
      • WeightBoundary: Yes or Not
      • NumApproxPoints
      • Tolerance
  • Join only coplanars:

A group of surfaces must be selected, and automatically are detected subgroups of planar parts that are joined in single planar surfaces.

    • TolAngle could be set to determine when two surfaces are coplanar


Join volumes:
Two or more volumes connected by shared surfaces are joined in a single one.
By default, if 'NoDeleteOriginalVolumes' was set, the source volumes and its dependent entities will be deleted.
Geometry Menu>Edit>Lines operations
Menu: Geometry->Edit->Line operations
With this option you can edit groups of lines with respect to their topology and shape.
Join lines end points:
With the command Join lines end points, two lines must be selected. GiD determines the distance between the two closest endpoints, draws both points, and asks for confirmation. If one of the lines is a polyline, interior points are also considered. If accepted, the points are converted into one and the lines are distorted. The new point will then take the place of the first line's point.
(See Move point for another method of converting two points to one.)
Caution: The second selected line cannot have higher entities (the second point is moved to the first).
Force to be tangent:
With the command Force to be tangent, two lines (which share at least one point) must be selected. They must be NURBS lines, otherwise they will be rejected. You are asked to enter the maximum angle between lines to accept the operation, and GiD will modify the selected NURBS lines and force them to be tangents at their common point.
Geometry Menu>Edit>Swap arc
Menu: Geometry->Edit->Swap arc
This command lets you select and alter arcs. Lines that are not arcs are rejected. When you confirm the operation, the arc is converted to a new arc with the same center and in the same plane but opposite the old one. The old arc disappears and the angle of the new arc will be complementary to the angle of the old arc.
Caution: Arcs belonging to higher entities cannot be swapped.

Geometry Menu>Edit>Polyline
Menu: Geometry->Edit->Polylines
Explode polyline:
This command lets you select which polylines you wish to explode; lines that are not polylines or have higher entities or conditions are rejected. After confirmation, the polylines are exploded and converted back to their original lines. Polylines then disappear (see Polyline).
Edit polyline:
The command Edit Polyline allows you to select which polylines you wish to edit; lines that are not polylines are rejected. It is possible to choose several options for the polylines:

  • Use points: When meshing this polyline, there will be at least one node at every point location that defines the polyline. These will be the endpoints of interior lines.
  • Not use points: When meshing this polyline, the mesh generator ignores the points and therefore the nodes will be placed anywhere. This is the default option. Nodes will only be put in the position of a point if there is a 4-sided surface over a part of a polyline (see Automatic 4-sided surface creation).
  • Only points: When meshing this polyline, the nodes will only be placed where the geometry points are.

Note: If one condition is assigned to one interior point of a polyline (see Conditions), one node of the mesh will be placed over that point.
Geometry Menu>Edit>SurfMesh
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.


Geometry Menu>Edit>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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