External Boundary
Define the outer extent of the model domain.
Define the outer extent of the model domain.
The external boundary is the closed outer polyline that delimits the analysis domain. Everything inside it is soil; everything outside is ignored. Material regions, the water table, and slip surfaces are all interpreted relative to this boundary, so it is normally the first thing you draw in a new model. A model has exactly one external boundary.
Drawing the external boundary
- Click Draw Boundary in the Geometry panel.
- Place vertices by clicking on the canvas, or type coordinates in the command input
(
x,yor@length<angle). - Click Close Boundary to close the polyline back to the first vertex.
The boundary must have at least 3 vertices. It is treated as a closed polygon, so you do not need to repeat the first point — closing the boundary connects the last vertex back to the first.
Keep the boundary simple
Draw the boundary as a simple (non-self-intersecting) polygon. Self-crossing outlines produce an ambiguous domain and unreliable slip-surface geometry.
Requirements
| Requirement | Detail |
|---|---|
| Vertices | Minimum 3. |
| Closure | Closed polygon (the editor closes it for you). |
| Count | One external boundary per model. |
Editing
Switch to Edit Vertices mode to adjust the boundary. You can move, insert, or delete vertices, drag the whole boundary with Move Boundary, or type exact coordinates in the vertex editor or the Coordinates tab of the properties pane.
Use Clear Boundary to delete the external boundary entirely. The Expand/Shrink External tool lets you grow or shrink the domain by drawing a polygon that intersects the current boundary.
Related
- Material Regions — subdivide the domain.
- Geometry Overview — full entity catalog and editing tools.