Operator TRAC
                                             DATE     99/01/06

    Directive TRACER                           See also :DESS 
    ----------------                                     @PLOTPRI 
                                                         @B_TPO2D 
    The TRAC instruction enables the user to plot severaltypes of 
 objects.

    ---------------------
    |  1st possibility  |
    ---------------------

    TRAC ((OEIL1) si 3D)|  ('QUAL')                      | OBJET1 ;
                        |  ('NOEUD')                     |
                        |  ('COUL'  ( COUL1 ) )          |
                        |  ('ELEM')                      |
                        |  ('CACH')                      |
                        |  ('FACE')                      |
                        |  ('ECLA'  ( RAPP1 ) )          |
                        |  ('COUPE' POIN1 POIN2 POIN3 )  |
                        |  ('SECT'  POIN1 POIN2 POIN3 )  |
                        |  ('TITR' 'bla bla...')         |
                        |  ('NCLK')                      |

    Description :
    _____________

    The TRAC instruction does not modify the OBJET1 object, but
 plots it on the graphic unit specified in " OPTION TRAC .. ".

    Contents :
    __________

    OBJET1 is either a MAILLAGE type object or a RIGIDITE type object.
 In the second case, it is the mesh underlying the stiffness that is
 plotted. This enables the user to get the contour of a structure with
 boundary conditions.


    OBJET1  : object to be plotted (MAILLAGE or RIGIDITE type).

    OEIL1   : viewpoint (in 3D) (POINT type) (optionnal)
              the contour is plotted by isometric projection.

    'QUAL'  : key word indicating that the names of the entities on
              the drawing will be displayed.

    'NOEUD' : key word indicating that the current node numbers will be
              mentioned on the drawing.
              CAUTION : the numbering is different after every TASS
                        instruction and at the beginning of every
                        SORT instruction.

    'COUL'  : key word indicating that only the elements whose color
              has been specified by COUL1 (MOT type) - or by the
              default color if COUL1 is not specified - will be
              displayed.

    'ELEM'  : key word indicating that the local numbers in each
              elementary object will be mentioned on the drawing.
              An elementary object is composed of a single type
              of element.

    'CACH'  : key word indicating that only the visible parts of the
              object will be displayed.

    'FACE'  : key word indicating that the representation is made
              by covering the faces of the element.

    'ECLA'  : key word indicating that the drawing will be plotted
              in splitting the elements. Each element will be
              represented by an homothetic transformation ratio
              RAPP1 (FLOTTANT type) equalling 0.5 by default.

    'COUPE' : key word indicating that only the part situated beyond
              the section plane with respect to the eye, and defined by
              three points POIN1, POIN2 and POIN3 (POINT type) is
              plotted.

    'SECT'  : key word indicating that only the intersection with the
              section plane defined by three points POIN1, POIN2 and
              POIN3 (POINT type) is plotted.

    'TITR'  : Modification of the title of the plot.

    'NCLK'  : suppress user input to end the display (X).


    ---------------------
    |  2nd possibility  |
    ---------------------


    TRAC  ('CACH') ((OEIL1) si 3D)   DEFO1
                                   (('DIRE') 'COUPE' POIN1 POIN2 POIN3);
                                   ('SECT' POIN1 POIN2 POIN3);
                                   ('ANIME')
                                   ('OSCIL')
                                   ('TITR' 'bla bla...')
                                   ('NCLK')
                                   ('FACE') ('FACB') ('FSDB')

    Description :
    ____________

    The TRAC instruction is used to plot the contour of a deformed
 object in the same way as that of a MAILLAGE type object.

    Contents :
    _________

    DEFO1   : deformed object to be plotted (DEFORME type).

    OEIL1   : viewpoint (only in 3D) (POINT type) (optional).

    'COUPE' : key word indicating that only the part situated beyond
              the section plane with respect to the eye, and defined by
              three points POIN1, POIN2 and POIN3 (POINT type) is
              plotted.

    'SECT'  : key word indicating that only the intersection with the
              section plane defined by three points POIN1, POIN2 and
              POIN3 (POINT type) is plotted.

    'CACH'  : key word indicating that only the visible parts of the
              object are plotted.

    'ANIME' : key word indicating, when the graphic system enables you
              to do it, that the successive deformed shapes contained
              in the DEFO1 object should be displayed in animation.

    'OSCIL' : key word indicating, when the graphic system enables you
              to do it, that the successive deformed shapes contained
              in the DEFO1 object should be displayed in animation.

    'TITR'  : Modification of the title of the plot.

    'NCLK'  : suppress user input to end the display (X).

    'DIRE'  : allow to specify the orientation of the observer view
              window:
              vi=(POIN1 'MOINS' OEIL1) defines the view direction
              ve=part of (POIN2 'MOINS' POIN1) orthogonal to vi defines
                 the vertical direction of the view window
              POIN1,POIN2,POIN3 define the view plan

    'FACE'  : allow to intensify the colour of the deformed object
              according to the orientation of each element normal
              with respect to the view direction. The mesh is plot
              according to the colour of the element.

    'FACB'  : idem 'FACE' but the mesh is plotted in white.

    'FSDB'  : idem 'FACB' without tilling of the face.

    Note :
    ________

    The DEFO1 object may contain a VECTEUR type object in which case
 it will be plotted on the deformed shape.

   The only possible options are 'CACH' and 'COUPE'.

    ANIME performs a simple animation of DEFO1, OSCIL carries out an
 oscillation between the deformed shapes.

    DIRE allows to generate plots even when the point of view is inside
 the object to plot.

    FACE, FACB and FSDB are supported accross the mif interface.


    ---------------------
    |  3rd possibility  |
    ---------------------

    TRAC ('CACH')((OEIL1)
             si 3D |('COUPE' POIN1 POIN2 POIN3)|) VEC1 OBJET1
                   |('SECT' POIN1 POIN2 POIN3) |
                   ('TITR' 'bla bla...')
                   ('NCLK')

    Description :
    ____________

    The TRAC instruction plots the VEC1 object of VECTEUR type through
 arrows. This contour is superimposed on that of the OBJET1 object
 (MAILLAGE type).

    The only possible options are 'CACH' 'COUPE' 'SECT' 'TITR' and
    'NCLK'.



    ---------------------
    |  4th possibility  |
    ---------------------


    TRAC  ('CACH') ((OEIL1) si 3D) |('COUPE' POIN1 POIN2 POIN3 )|   ...
                                   |('SECT' POIN1 POIN2 POIN3 ) |

  ... (N1)   (LREEL1) | CH1   | OBJET1          | ( OBJET2 )   (VEC1) ;
                              | DEFO1           |
                      | MODL1 CH2 (DEFO1) (CH3) |
            ('TITR' 'bla bla...')
            ('NCLK')

    Description :
    ____________

    The TRAC instruction plots a field in the form defined in OPTION
 ISOVALEUR, i.e. either through a network of isovalue curves, or in
 covering the areas containing different values with different
 colors.

    In case of a multicomponents MCHAML, the Vonmises (for a field of
CONTRAINTES subtype) or the first component is plotted. Then, an other
component can interactivly be choosed.

    Contents :
    _________

    OEIL1  : viewpoint (POINT type) (only in 3D) (optional).

    CH1    : field to be plotted (CHPOINT type).

    MODL1  : model (MMODEL type) (not used to choose the object
             to plot).

    CH2    : field to be plotted (MCHAML type).

    CH3    : field of caracteristiques (for computation of Vonmises
             for shell beam and pipe elements).

    LREEL1 : list of the values according to which the isovalues are
             displayed (LISTREEL type).
             Their number cannot exceed 14 (in PostScript output).

    N1     : allow the specification of the number of wanted isovalues.
             The values are automatiquely determined.

    OBJET1 : object (MAILLAGE type) used to plot the field by
             interpolation in case of CHPOINT.

    OBJET2 : object (MAILLAGE type) plotted when supplied. If OBJET2
             is not supplied, OBJET1 is plotted; otherwise, it is
             the OBJET2 that is plotted.

    'CACH' : key word indicating that only the visible part of the
             plotted object is displayed.

    'COUPE': key word indicating that only the part situated beyond
             the section plane with respect to the eye and defined by
             three points POIN1, POIN2 and POIN3 (POINT type) is
             plotted.

    'SECT' : key word indicating that only the intersection with the
             section plane defined by three points POIN1, POIN2 and
             POIN3 (POINT type) is plotted.

    VEC1   : if VEC1 (VECTEUR type) is provided, it is also represented
             on the contour.

    DEFO1  : if the DEFO1 object (DEFORME type) containing a single
             deformed shape is supplied instead of OBJET1, the deformed
             object will be plotted.
             In this case, it is not possible to provide the VEC1
             object.
             However, this object may be a part of the DEFO1 object.


    The only possible options are 'CACH' 'COUPE' 'TITR' and 'NCLK'.

    ---------------------
    |  5th possibility  |
    ---------------------

    TRAC (OEIL) ARET |  ('CACH') | OBJET1 OBJET2
                   |  ('FACE') |
            ('COUPE' POIN1 POIN2 POIN3) ;
            ('SECT' POIN1 POIN2 POIN3) ;
            ('TITR' 'bla bla...')
            ('NCLK')


    Description :
    ____________

    The TRAC instruction plots the mesh OBJET2, obtained by means of
    the ARETE operator from the mesh OBJET1, by dealing with the hidden
    parts.