Creating a Matching Constraint

Open the Constraint1.CATPart document.
Make sure the Constraints option is selected in Tools > Options > Infrastructure > Part Infrastructure > Display tab, so that you are able to see the constraints in the specification tree.

1. Click Matching Constraint  in the FreeStyle Constraints toolbar.

   The Match Constraint dialog box displays.

   The continuity constraint created appears in the specification tree under the Free Form Constraint.X as given below. In the Match Constraint dialog box you can: Elements: Manages elements involved in the continuity constraint: Source: The element to be deformed; an edge for surface matching, a vertex for curve matching. Target: The reference element; an edge, a plane, a curve or a vertex. Swap: Swaps the source and target elements. Options: Partly: The matching surface meets the edge of the reference surface partly, manipulators appear to move the two meeting points. Inside: Projects the boundary on the target surface. This option is only available if Exact is not selected. If this option is selected, Exact options are grayed out. On basic geometry: Matches curves or surfaces with the underlying geometry i.e. considering the trimmed elements.   With On basic geometry option ON     With On basic geometry option OFF Diffusion: Modifies a maximum of ranks of control points in the element to be deformed, otherwise only the first rank is modified. Adapt: Adapts the transversal order of the surface to be matched with the transversal order of the target surface. This option is available only of the target edge is an isoparametric of its support surface. Auto Apply: Performs the deformation of the surface to be matched each time you modify an option. Continuities: There are two types of algorithm that can be used together; the exact algorithm and the approximated algorithm. If both of them are used, the first one to be performed is the exact one, then the approximated. Exact: The first rank of control points of the element to be deformed takes a regular distribution according to the target element. Other ranks keep their distribution. Available orders of continuity for this algorithm are: / G0 (selected/cleared) / G1 (selected/cleared) / G2 (selected/cleared) Approximated: The distribution of the first rank of control points of the surface to be deformed is kept as is. Other ranks keep their distribution. Available orders of continuity for this algorithm are: / G0 (selected/cleared) / G1 (selected/cleared), only for the start and the end of the edge. / G2 (selected/cleared) only for the start and the end of the edge. The position of the start and end transversal boundaries is blocked. The value of the continuities on these edges does not impact the position of the boundaries. / unlink/link orders of continuity for the start and the end of the edge. Support: Defines the direction in which the control points is projected. Along direction: If this option is cleared the movement is along the local normal of the target element. If this option is selected the movement of control points depends on the propagation mode selected. The following modes are available which define the projection direction: Along View: The direction is along the view direction. The control points move along the depth of the viewpoint. To see the control point movement rotate the part. User Line/Plane: The direction is along the selected line or normal to the selected plane. The compass option is available only with this mode. Right-click the compass selection field and select the axis or plane. Using the contextual menu you can create the required element. If Compass is ON, you can set this direction by manipulating the compass in 3D.  Along Source: The direction is along the source element. Deviations: Displays the deviations according the orders of continuity.

2. Select the edge of the surface to be matched.

   The boundary is highlighted.

3. Move the pointer onto the second surface.

4. Click the surface when the adequate boundary is highlighted.

   As the Partly option is selected, two green manipulators represent the projection of the source element onto the target element. These manipulators can be moved along the edge.

5. Click Apply.

   The surface is modified according to the options.

6. Clear the Partly option and click Apply again.

   The surface is modified on all the edge.

   Right-click the continuity type to display the contextual menu, you are able to: Modify the chosen type: Point continuity (G0), Tangent continuity (G1),Curvature continuity (G2) or G3 continuity (G3). Activate/Deactivate: Activates/deactivates the constraint. Update Network: Updates the constraints linked ones with the others, from the selected constraint and while taking into account their creation order. Apply Constraint: Updates locally the constraint. Delete: Deletes the constraint.

7. Click OK in the Match Constraint dialog box.

   Click OK button does not perform the Apply operation.

8. Create several constraints like these.

9. Right-click the G0 (tangent) continuity as show and change the continuity type to G2 (curvature).

10. Click the G2 (Curvature) continuity arrow to reverse the direction of the constraint.

11. Right-click a G0 continuity and deactivate it.

    Color of the continuity indicates its activating status: White, activated. Green-yellow, deactivated.

12. Select the Surface.2 and click Control Points in Shape Modification toolbar to display the control points and mesh lines on the surface, allowing you to dynamically modify them.

    The source surface deforms so that the neighboring constraints are automatically updated. Note that the deactivated constraint is not taken into account.

    You can create as many constraints as there are elements. You can deactivate the constraints using the Deactivate contextual menu. Constraints created using this command are very similar to the constraints created in the Part Design and the Sketcher workbenches: they are compatible and are solved using a variational approach.

13. Click Cancel in the Control Points dialog box.

14. Select the Surface.2 and click In Model or on Perch in the Quick Compass Orientation toolbar, to switch the compass from the perch to the selected surface, see Managing the Compass.

15. Use the compass to move the surface.

    All the constraints are updated accordingly, except the deactivated constraint.

• If you want to delete a constraint, delete it in the specification tree, under the Free Form Constraint.X node. However, it is also possible to delete the constraint using the contextual menu or in the 3D, by selecting the constraint and hit Delete key.
• You can get the result of multiple constraints surface is a mean surface between each constraint result by selecting Mean Surface Solver option in Tools > Options > Shape > FreeStyle > General tab, Matching Constraint command options area. If a surface is modified by two constraints, the results for the two constraints are computed separately. The final result is a mean surface between those two intermediate results.
• If several constraints are linked together and either the target or source element of a constraint is modified, then all the linked constraints are updated. The constraint taking the modified element as its input is updated  last. This is to ensure that the continuity is maintained on the modified element.
  
  After the update process, the continuity created by the constraint that is not the last one to be updated may not be met. In such a case use the Apply Constraint contextual menu on the constraint.

Open the Constraint2.CATPart document.
Select Mean Surface Solver option in Tools > Options > Shape > FreeStyle > General tab, Matching Constraint command options area.

Constraints can only be set on datum elements.