About the Extraction of Geometry

You can extract the elements and sub-elements from the surface and volumes. Here is a basic information needed when extracting elements.

Related Topics
Extracting Elements
Extracting Sub-Elements

Complementary Mode

Select the Complementary mode check box to highlight and therefore select the elements that were not previously selected, while deselecting the elements that were explicitly selected.

Warning:
  • This option is disabled if the extracted element is a point or a volume.
  • If the selected element has a defined support and is not a surface, even though the Complementary mode option is selected, it will not be taken into account for the extraction and the option will therefore be inactive. After the extraction, the option will be available again.
  • For the Multiple Extract command, this option applies to all the inputs that lie on the same support.

Parameters for Curves

Click Show parameters>> to display further options, applicable to curves only.


  • Distance Threshold: specifies the distance value between 0.001mm and 0.1 mm below which the elements are to be extracted.
    Important:
    • The default value is 0.1mm, except if a Merging Distance has been defined different from 0.001mm in Tools > Options > Shape > Generative Shape Design, General tab. In this case, the Distance Threshold value is initialized with the Merging Distance value. For more information, refer to General Settings in the Customizing section.
    • This option is available with all propagation types, except for the No propagation type.
  • Angular Threshold: specify the angle value between 0.5 degree and 5 degree below which the elements are to be extracted (the default value is 0.5deg)
  • Curvature Threshold: specifies a ratio between 0 and 1 which is defined as follows:

    if ||Rho1-Rho2|| / max (||Rho2||,||Rho1||) < (1-r)/r where Rho1 is the curvature vector on one side of the discontinuity, Rho2 the curvature vector on the other side, and r the ratio specified by the user; then the discontinuity is smoothed.

    For instance, r=1 corresponds to a continuous curvature and r=0.98 to the model tolerance (default value). A great discontinuity will require a low r to be taken into account.

    Curvature Threshold = 0.98

    Curvature Threshold = 0.80

    Curvature Threshold = 0.50

Tips:
  • When Point continuity is selected, only the Distance Threshold is activated
  • When Tangent continuity is selected, both Distance and Angular Thresholds are activated
  • When Curvature continuity is selected, Distance, Angular and Curvature Thresholds are activated.

Contextual Extracts

Some commands allow the creation of contextual extracts using the right-mouse button. They are aggregated to the feature using them and put in No Show. Here is an example with the Parallel Curve command when right-clicking the Curve box:


  • If you select the Create Extract contextual command, the Extract Definition dialog box appears.
  • If you select the Create Extract (in point) or Create Extract (in tangency) contextual command, no dialog box appears.
  • If you select the Create Multiple Extract contextual command, the Multiple Extract Definition dialog box appears.
Important:
  • These commands let you create extracts with a pre-defined propagation. You just need to select a sub-element such as a surface edge, border edges, face, sub-elements of a volume or a solid.
  • You need to leave the pointer on the pre-selected sub-element to preview and compute the propagation (in green):

Internal Edges and Support

If you extract an internal edge, you are advised to select a support element so that the orientation of the resulting extract feature remains the same even if the geometry is modified. If you extract an internal edge using the Point Propagation type and there is an ambiguity about the propagation side, a warning message is issued and you are prompted to select a support surface. In this case, the Support box becomes active.

Note: If the selected element is a border edge, the propagation is done along the boundary of the support and does not take into account internal edges.

User Selection Filter

If either Intersection edges activation or Tangent Intersection edges activation icon is selected in the User Selection Filter toolbar before launching the Extract command, then the Geometrical Element Filter icon is automatically activated and the Propagation type set in the Extract Definition dialog box is applied.

Deactivate the Geometrical Element Filter icon to take into account the behavior of the Intersection edges activation or Tangent Intersection edges activation capability.

When you click OK in the Extract Definition dialog box, the status of the Geometrical Element Filter icon returns to normal.

For further information, refer to CATIA Infrastructure User's Guide : Selecting Using a Filter.

Extraction of Volumes

You can extract the elements from volumes. To do so, you can either:

  • select the volume in the specification tree, or
  • use the User Selection Filter toolbar and select the Volume Filter mode. For further information, refer to CATIA Infrastructure User's Guide : Selecting Using a Filter.

In both cases, the result of the extraction is the same whatever the chosen propagation type.

Miscellaneous


  • In a document containing several 3D shapes, you can use the multiple extract capability in the current 3D shape from the selection of an element in another 3D shape, provided the propagation type is set to No Propagation. In this case, a curve (respectively a surface or point) is created in the current 3D shape if the selected element is a curve (respectively a surface or point); the parent therefore being the created curve (respectively the surface or point).
Important:
  • If another propagation type is selected, the extraction is impossible and an error message is issued.
  • When editing the extract, you can change the propagation type providing the parent belongs to the current 3D shape.
  • In the current 3D shape, if you select an element using the Tangent, Point or Curvature continuity as the Propagation type, a warning is issued and you have to select No propagation instead.

  • If the selected element is not continuous in tangency and the propagation type is set to Tangent continuity, an error message is issued.
  • If the selected element is a wire that is not curvature continuous and the propagation type is set to Curvature continuity, an error message is issued.
  • When the result of an extract is not connex (during creation or edition), you can now select the part to keep to solve the ambiguity.
  • If two elements have a same name and their centers of gravity are distant of less than 0.1mm, the naming ambiguity mechanism fails and an error message is issued.
  • You cannot an extracted element from a document to another. If you want to do so, you need to copy/paste the initial element first into the second document then perform the extraction.
  • If there is several solutions for the propagation, the computation of the extract stops at the junction point.