Selecting Implicit Elements

There are many ways of selecting geometrical elements either in the geometry as described in the CATIA Infrastructure User's Guide, Selecting Objects section, or in the specification tree.

However, specific to wireframe and surface elements are some implicit elements, such as the axis of a cylinder, or the vertex of a cone for instance, participating in the creation of a feature yet not directly selectable as a separate element.

This task shows how to select these implicit elements.

Open the Implicit1.CATPart document.

  1. Click Spline and successively select the four points.

    The Spline Definition dialog box looks like this:
  2. Select Point.3 from the list, to impose a tangency constraint on this point.

    Note that you cannot select the cylinder's surface.
  3. Press and hold the Shift key, then move the pointer over the cylinder.

    The cylinder's axis is automatically detected as a selectable element to indicate a direction, and displayed.
  4. Click anywhere on the cylinder's surface, still holding the Shift key pressed down.

    The tangency constraint direction, based on the cylinder's axis, is displayed at the selected point.
  5. Click OK to create the spline tangent to the cylinder at the selected point.