Job: Setting constraints on Control Points

This document explains how to set constraints on the control points of a selected surface when using the Surface through Control Points command.

1 After selecting the surfaces to be modified, expand the Constraints node in the selection list.
 
2 First of all, define the constraints you want to apply. To do this, in the Mode drop-down list, select Define constraints.

Defining constraints on control points and applying them
Note that at this stage you will just define the constraints you need to apply and select the control points you want to apply them to.
When you're done with the definition of constraints, you will change the Mode to Move control points and you will see that the surface control points will be enabled to move only according to the constraints you have set.

For details on how to control the distribution of motion for control points, see "Using the Distribution law options".
 
3 In the Type: drop-down list, choose the constraint you want to apply.

Reference entity management
When defining constraints, you will typically use reference objects, such as lines, planes, curves or surfaces. If the object you use as a reference is an active object (that is: an object selected among the ones to be edited), the Static check box will show up.
  • When the box is checked, the shape of the reference object (from now on: the shadow) to be used is the one it had at the time it was selected.
  • When the box is cleared, on the contrary, the reference object will be updated based on its current shape.
So, the actual meaning of Static is to use a static representation of the object during the editing operations.

Parallel to axis The selected Points will be constrained to move in a direction parallel to that of a selected Axis (see "How to define an axis or line").
On to axis The selected Points will be constrained to move on a selected Axis.
Parallel to plane The selected Points will be constrained to move on a plane parallel to the one you can specify as described in " How to define a plane".
On to plane The selected Points will be constrained to move on the selected plane which can be specified as described in " How to define a plane".
Orthogonal to plane The selected Points will be constrained to move on a plane orthogonal to the selected one which can be specified as described in " How to define a plane".
Parallel to curve The selected Points will be constrained to move keeping parallel to a selected curve ( Curve).
On to curve The selected Points will be constrained to move on a selected curve ( Curve).
Orthogonal to curve The selected Points will be constrained to move orthogonally to a selected curve ( Curve).
Parallel to surface The selected Points will be constrained to move keeping parallel to a selected surface ( Surface).
On to surface The selected Points will be constrained to move on a selected surface ( Surface).
Orthogonal to surface The selected Points will be constrained to move orthogonally to a selected surface ( Surface).
Radial to Point The selected Points will be constrained to move radially about a selected Radial origin.
Radial to Axis The selected Points will be constrained to move radially about a selected Axis.


Constraint groups
Any time you complete the definition of constraints for the selected control points, a new Constraint group item shows up in the selection list so as to enable you to select another set of control points to which you can apply different constraints.

4 When you're done with setting the constraints, set the Mode drop-down list to Move control points and move the control points.

Snap to markers
When the Snap to markers check box under More Options is selected, you will be enabled to move a control point and snap it exactly to another one, which is not possible when the check box is not selected.


Visibility of cursor, markers and curve "shadows"
The check boxes available by expanding the Drag display node under More Options enable you to control the visibility of the cursor, control point markers and shadows during mouse drag operations. Turning visibility off can be useful when the involved entities are complex, to better visualize the shape and the location of the curve during the operation.
Cursor When selected, the cursor is visible during mouse drag operations. When not selected, the cursor is not visible.
Markers When selected, control points markers are visible during mouse drag operations. When not selected, control points markers are not visible.
Shadow When selected, shadows of the reference entities are visible during mouse drag operations. When not selected, shadows are not visible.
Tips and Tricks