Comparing Models with the Detailed Method

You can compare two versions (3D shape representations) of a model with the Detailed method.

See Also
About Comparing Models (Detailed or Quick)
Comparing Models with the Quick Method
Using the Viewer in Compare
In the Knowledge Base
Issue with positioning of graphical representations of Surface Connection Checker
  1. Open the first 3D shape representation to compare (Content 1).
  2. From the Analysis section of the action bar, click Compare.
  3. Select the second 3D Shape Representation (Content 2).
  4. Edit the Distance used for the comparison.

    Under this distance, two faces or areas are considered as identical.

  5. From the Method list, select Detailed.
    The comparison is carried out on the areas.
  6. Select a meshing mode from the list.

    • Large, Medium, Precise are automatic modes.
    • User Parameters lets you decide of the Sag (chordal error) and the Step (maximum length of the edges of the mesh) values.

      The meshing starts with the Sag and Step values you have entered, but Compare may use other values to optimize the meshing.

      • A small value of Step creates a mesh with many triangles, and thus increases the quality of the comparison.
      • Sag applies to models with curvatures. A small value of Sag in those models creates a mesh with many triangles and thus increases the quality of the comparison.
      • You have to experiment the best values. They depend on the geometric characteristics of the surfaces to compare. When the differences are small in comparison with the model size, it may be difficult to tune up the parameters for finding the differences within an acceptable time span.
      • Small values are time-consuming.

    The comparison is based on points sampled on the meshed surfaces

    • The boundaries of areas are approximate.
    • The differences smaller than the Step may be either not detected or detected in one model only (the original or the comparison model).
    • In case of geometric singularities of the surfaces (for example thin surfaces, twisted surfaces) the computation of differences may be altered.

  7. Optional: Select Topological to search topological differences.
  8. Click Compute:

    The comparison is made on all shown surfaces or solids. The number of areas found for each type appears in the dialog box. Those areas are highlighted in the work area.

  9. Click Merge Options.
  10. Select the required check boxes:
    • Geometrical Set to copy areas into different geometrical sets, see below for more information.
    • Selection Set to place areas into different selection sets.
    • Color to display areas in given colors.
    • Full name to display the full name of areas in the tree.

    In the tabs described below, consider areas to be clouds of points delimited by curves, and surfaces. When you retrieve an area, you retrieve the clouds of points, the curves, and the surfaces associated to the areas.

    • In the Geometrical Set tab, you can select the type of areas you want to copy, and edit the names of the geometrical sets to contain them.
    • In the Selection Set tab, you can select the type of areas you want to put in selection sets and edit the names of those selection sets.
    • In the Color tab, you can select the types of faces you want to visualize and edit the visualization color.

    Notes:
    • The check boxes and colors that are proposed correspond to those selected in previous steps.
    • The selection of Full name check box is optional but you must select at least one of the other three check boxes (Geometrical Set, Selection Set or Color). You can select as many check boxes as required (up to all).

  11. Select the Destination:
    • New
      • Clouds of points, surfaces, and curves from both models are copied to this 3D part.
      • Clouds of points, surfaces, and curves are sorted in the dedicated geometrical sets.
    • Original
      • Clouds of points and curves computed from both models are copied to the original 3D shape representation (Content 1).
      • Surfaces from the comparison model are copied to the original 3D shape representation.
      • Regarding the surfaces already present in the original model, their behavior depends on whether or not Geometrical Sets is selected or not, see below.

Identical, added, and removed areas are extracted or computed from the compared models as clouds of points, surfaces, and curves and are processed as follows:

  • Geometrical sets are created: If you have selected the Geometrical Set check box, all required geometrical sets are created. This option is relevant when Destination is Original and lets you duplicate the surfaces from their original containers to the geometrical sets dedicated to the result of the comparison. Otherwise they would not be duplicated.
  • The Identical areas Geometrical Set contains two geometrical sets:
    • One for the clouds of points and surfaces that are complementary to the added clouds of points, surfaces and curves. They correspond to identical areas extracted from the comparison model,
    • One for the clouds of points and surfaces that are complementary to the removed clouds of points, surfaces, and curves. They correspond to identical areas extracted from the original model.
    The number of identical areas may be different in these two geometrical sets, mainly because the number of areas depends on the face limits that can differ between the two models.
  • The selection sets dedicated to the comparison are created only when the Selection Set check box is selected, and they apply to the comparison results. If previous selection sets existed in the 3D shape representations before the comparison:
    • They are lost if Destination is New.
    • Those present in the comparison 3D shape representation are lost if Destination is set to Original, whereas those of the original 3D shape representation still exist.
  • Clouds of points, surfaces, and curves are painted only when the Color check box is selected.
  • As duplicate or embedded faces are ignored (considered as in NoShow), if a counterpart face is found in the other 3D Shape Representation, it is placed in the Different faces count, but the ignored faces are not copied to a geometrical set, or placed in a selection set, or displayed in a given color. In extreme cases, the geometrical set containing only ignored faces is not created.
Notes:
  • The result areas are connex but given on a surface level, not on a global one.
  • The curves corresponding to the boundaries of the areas are of two types:
    • Exact curves corresponding to face limits.
    • Approximate curves, for the other cases. Those curves are not supported by the model faces.
  • Some boundaries can be given through non-limited curves.

  • Internal curves are not considered in the boundary and are not displayed but in some cases, internal curves may appear because of an algorithm limitation:
    • A boundary can be included in a surface or can be a portion of a 'natural ' boundary:

    • The area is shared by four faces. The boundary should be:

    • However the result may appear like this:

      where

      is not expected. This curve is a boundary of the surface.

      It is not the boundary of the area. It is an internal curve.
  • Compute displays areas, whereas Merge Options deal with areas made of cloud of points, limiting curves and associated surfaces.

    Compute is less accurate than the result of merge.