Mirror and Close

The Mirror and Close option allows you to automatically close a boundary with a mirror image of the current boundary polyline.

This is a convenient time-saving option if you are defining a complicated, closed symmetric boundary. It allows you to define half of a boundary, and then complete the remainder with a single mouse click. For example, this would be useful for a symmetric tunnel boundary which is composed of several arc segments.

To use Mirror and Close:

1. Select the desired Add Boundary option (e.g. Add Excavation, Add Stage, etc).
2. Enter exactly one-half of the boundary polyline, such that the axis of symmetry of the boundary is defined by an (imaginary) straight line through the first vertex and the current (last) vertex you have entered.
3. Right-click the mouse and select Mirror and Close from the popup menu. The boundary will be automatically closed with a mirror image of the current polyline.

NOTES:

• The axis of symmetry does NOT have to be horizontal or vertical. The axis of symmetry can be at any orientation, and is represented by a straight line through the first vertex and the current (last) vertex you have entered. Experiment with this option to see how it works.
• At least three vertices must be entered before the Mirror and Close option is enabled.