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2.4 Three-dimensional meshes REFEXX

 

REFEXX is used to visualize three-dimensional or two-dimensional meshes (in the latter case, it adds a third null coordinate to each point). It also offers numerous mesh manipulation and checking possibilities. It can also be used for assigning reference or sub-domain numbers to mesh items.

Differing from other graphics modules, REFEXX uses the principle of roll-down menus to define the numerous choices available.

The presentation of the screen, shown in figure 2.14, consists of several windows:

 
Figure 2.14: Organization of the windows of REFEXX 

The commands can be defined in two ways:

In this manner, we move around in the tree until the desired action is selected. The inverse operation (return in reverse), is performed in the following manner:

The menus consists of two types of action:

2.4.1 Aim and utilization limits

As briefly indicated above, the aim of REFEXX is to plot meshes and manipulate them. In more detail, we can:

The element quality checking corresponds to tetrahedra only.

2.4.2 Utilization of REFEXX

  1. Activate preprocessor REFEXX.

  2. Choose the output terminal.

  3. The main menu appears (see below) in window F2.

  4. Enter, in window F4, the name of the file containing the mesh (validate by clicking on the return key).

  5. The MODULEF main menu appears.

  6. An automatic plot is obtained by refreshing the screen. To do this, we go to the sub-menu "MODIFIER LA VISU..." (by clicking on it in the main menu) and then click on "RAFRAICHIR". More directly, the user can type "RAF", the equivalent keyword (after typing RAF and returning, we note that window F2 is in the state it would have been if we proceeded as indicated initially).

2.4.3 Complete description of REFEXX

The menus contain a certain number of choices, which are of two types:

Type 1:
the choice corresponding to the definition of an action (example "SAUVER LA SD") or a state (for example, choose a "COUPE OPAQUE"),
Type 2:
the choice is itself a menu containing two types of choices.

The main menu, "MODULEF", gives access to the following sub-menus: 

      MODULEF
         MODIFIER LA VISU
            TOURNER AUTOUR
            COUPER
            REFERENCES TRACEES
            ITEMS TRACES
            NUMERO
         INFO SUR OBJET
            REFERENCE POINT
         VERIF DU MAILLAGE
         AFFECTER REFERENCE
         REFERENCE PAR LOT
         CHANGER REFERENCE
         CONSTRUCTION DE BD
         TRANSFORMATION

Main menu: "MODULEF"

Access:
Basic menu, obtained at initialization. The user returns to it when quitting (keyword "Q" or ">> QUITTER") the sub-menus.

This menu is used to select the following items (we indicate the names of the possible options, the option type in italics, the equivalent keyword in UPPERCASE, and the corresponding description):

The secondary menu of menu "MODULEF..." is as follows:

 
Figure 2.15: Example REFEXX: automatic mode 

Sub-menu "MODIFIER LA VISU":

Access:
Via the main menu.

This sub-menu is used to select the following items:

The secondary menu "MODIFIER LA VISU..." is the following:

 
Figure 2.16: Example REFEXX: visible edges, coplanar edges eliminated 

Sub-menu "TOURNER AUTOUR":

Access:
Via the sub-menu, "MODIFIER LA VISU" of the main menu.

This sub-menu is used to select the following items:

The actions are accumulated (if compatible, those actions taken into account are in evidence in the menu) and and executed by clicking on "EXECUTION" in the secondary menu.

Note:
Once the action is evident in the menu, it will be executed at each screen refreshing (including in the case of a softcopy), thus, to delete it, it is necessary to re-click.

The secondary menu of the sub-menu "TOURNER AUTOUR..." is the following:

Sub-menu "COUPER:

Access:
Via the sub-menu "MODIFIER LA VISU" of the main menu.

The user can define:

The cut plane is defined with the aid of three points (click on the screen or enter their coordinates) or via its equation. The equation of the cut plane will appear in window F4. Otherwise, the points can be entered by mixing the two capturing methods possible in this case.

This sub-menu is used to select the following items:

The secondary menu of the sub-menu "COUPER..." is the following:

 
Figure 2.17: Example REFEXX: opaque cut 

Sub-menu "REFERENCES TRACEES":

Access:
Via the sub-menu "MODIFIER LA VISU" of the main menu.

In this sub-menu, the user selects those items to plot for which he/she enters the reference number (in the case of faces) and/or the sub-domain number (in the case of elements). It enables us to select the following items:

The secondary menu of sub-menu "REFERENCES TRACEES..." is given below:

Sub-menu "ITEMS TRACES":

Access:
Via sub-menu "MODIFIER LA VISU" of the main menu.

This sub-menu is used to define the plot type and to specify the visibility notions. It enables us to select the following items:

The secondary menu of sub-menu "ITEMS TRACES..." is given below:

 
Figure 2.18: Example REFEXX: solid line and elimination 

Sub-menu "NUMERO":

Access:
Via the sub-menu "MODIFIER LA VISU" of the main menu.

This sub-menu is used to display the number on the plot. The numbers may be item numbers (elements, points), or reference or sub-domain numbers. It enables us to select the following items:

The secondary menu of sub-menu "ITEMS TRACES..." is given below:

 
Figure 2.19: Example REFEXX: node numbers 

Sub-menu "INFO SUR OBJE":

Access:
Via the main menu.

This sub-menu is used to obtain information pertaining to the mesh under consideration. It enables the user to select the following items:

The secondary menu of menu "INFO SUR OBJE" is given below:

Sub-menu "VERIF DU MAILLAGE":

Access:
Via the main menu.

The module is used for certain mesh verifications. It can check that all elements have positive volumes.

It can also examine any element by animating it. To do this, we define a magnifying glass and designate an element in the cut plane (it is thus necessary to define an opaque cut, or a section beforehand). The element chosen is then visualized in the magnifying glass in animated mode.

It can also be used to plot the quality isovalues for elements in the cut plane. The color blue indicates good quality elements, whereas red is used for bad quality elements (option valid only on color screens).

The quality of a tetrahedron is defined by:

where is a normalization factor, h is the element diameter and is the radius of the inscribed sphere. An element with quality close to 1 is very good, whereas the more Q increases the more the element is degenerate.

The quality measurement is only valid for meshes composed of tetrahedra. For the others elements, it is necessary to complete function CRIQUA.

The sub-menu is used to select the following items:

The secondary menu of menu "VERIF DU MAILLAGE" is given below:

 
Figure 2.20: Example REFEXX: magnification and animation 

Sub-domain "REFERENCE POINT":

Access:
Via the sub-menu "INFO SUR OBJE" of the main menu.

This sub-menu is used to obtain information pertaining to a mesh point clicked on the screen. The following items can be selected.

The secondary menu of sub-menu "REFERENCE POINT..." is given below:

Sub-menu "AFFECTER REFERENCE":

Access:
Via the main menu.

This sub-menu is used to assign reference or sub-domain numbers to clicked items individually (point, edge, face or element). The following items can be selected:

The secondary menu of menu "AFFECTER REFERENCE..." is given below:

Sub-menu "REFERENCE PAR LOT":

Access:
Via the main menu.

This sub-menu is used to assign reference or sub-domain numbers to a group of items (point, edge, face or element). The following items can be selected:

The secondary menu of menu "REFERENCE PAR LOT..." is given below:

Sub-menu "CHANGER REFERENCE":

Access:
Via the main menu.

This sub-menu is used to change reference or sub-domain numbers of a group of items (point, edge, face or element) by specifying the correspondence between the number to change and the new number to assign to these items. The following items can be selected:

The secondary menu of menu "CHANGER DE REFERENCE..." is given below:

Sub-menu "CONSTRUCTION DE BD":

Access:
Via the main menu.

This sub-menu is used to construct a Data Base containing a mesh, or a part of a mesh. Two Ascii files are created:

A prefix is requested to name the files (prefix.coor, prefix.vol , prefix.points or prefix.faces according to the case).

The element definitions are considered as in a D.S. NOPO.

The above sub-menu is used to select the following items:

The secondary menu of menu "CONSTRUCTION DE BD..." is given below:

Sub-menu "TRANSFORMATION":

Access:
Via the main menu.

This sub-menu is used to perform geometric transformations on a mesh: linear transformations or input via a matrix. Several transformations can be stacked. Furthermore, it is possible to move the boundary points. The transformed mesh can be saved. The following items can be selected;

The secondary menu of menu "TRANSFORMATION..." is given below:

An example of geometric transformations is given in figures 2.21 and 2.22. The initial object, shown in the first figure, is dilated in the z-direction with a factor 1.5. The result is shown in the second figure (the two figures are softcopies).

 
Figure 2.21: Example REFEXX: initial mesh in automatic mode 

 
Figure 2.22: Example REFEXX: mesh after dilation 

2.4.4 Keyword-Action correspondence

General keywords:

For menu "MODULEF":

For sub-menu "MODIFIER LA VISU":

For sub-menu "TOURNER AUTOUR":

For sub-menu "COUPER":

For sub-menu "REFERENCES TRACEES":

For sub-menu "ITEMS TRACES":

For sub-menu "NUMERO":

For sub-menu "INFO SUR OBJE":

For sub-menu "REFERENCE POINT":

For sub-menu "VERIF DU MAILLAGE":

For sub-menu "AFFECTER REFERENCE":

For sub-menu "REFERENCE PAR LOT":

For sub-menu "CHANGER REFERENCE":

For sub-menu "CONSTRUCTION DE BD":

For sub-menu "TRANSFORMATION":

2.4.5 Plot descriptions

The plots presented (figure 2.15 to 2.20) were obtained by hardcopies:

Figure 2.15
: Execute REFEXX, type -1 (selection of terminal), enter the file name, type keyword RAF to view plot, type keyword HARD.

Figure 2.16
: Execute REFEXX, type -1 and enter the file name, go to menu "MODIFIER LA VISU" and deactivate the items "REMPLISSAGE FACE" and "ARETES COPLANAIRES", type RAF and then keyword HARD.

Figure 2.17
: Execute REFEXX, type -1 and enter the file name, go to menu "MODIFIER LA VISU" and deactivate "REMPLISSAGE FACE" and "ARETES COPLANAIRES", type RAF and then keyword HARD.

Figure 2.18
: Execute REFEXX, type -1 and enter the file name, go to menu "MODIFIER LA VISU" and choose "COUPER", in the sub-menu click on items "COUPE OPAQUE" and then "POINT ECRAN", designate three points on the object and click on item "EXECUTION", lastly, type the keyword HARD.

Figure 2.19
: Execute REFEXX, type -1 and enter the file name, go to menu "MODIFIER LA VISU" and deactivate "REMPLISSAGE FACE" and "ARETES COPLANAIRES" and click on "NUMERO", in this sub-menu click on "NOEUDS" and then click "EXECUTION", and lastly type HARD.

Figure 2.20
: Execute REFEXX, type -1 and enter the file name, go to menu "MODIFIER LA VISU" and choose "COUPER", in the sub-menu click on items "COUPE OPAQUE" and then "POINT ECRAN", designate three points on the object and click on item "EXECUTION". Return to menu "MODULEF" and choose "VERIF DU MAILLAGE". Define the display zone of the element(s) to examine by choosing "DEFINIR LA LOUPE", after which, by clicking on two points on the screen, a window appears. Click on an element in the cut pane, which is then displayed in the window. By clicking on "ANIMATION LENTE", for example, the current tetrahedron is animated, which can be viewed before going to another element. Lastly, type keyword "HARD".

The plots in figures 2.21 and 2.22 result from softcopies.

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