Straight-line objects are a special case of polylines in which all the line segments in the polyline are parallel to one of the edges of the grid. (With SUTRA models, straight lines are oriented parallel to X, Y or Z axes.) To create a straight-line object, the user does the following:

1.The user either selects Object|Create|Straight Line or clicks on the Create straight-line object button .

2.The user continues adding vertices as described with Polylines. Pressing the escape or delete key while creating an object deletes the last created vertex of that object. As with points, the Object Properties dialog box is used to specify the properties of the object.

If the Shift button is held down when the mouse button is clicked and there is a vertex on another visible object within 3 pixels of the cursor, the new vertex will be at the same location as the vertex on the other object.

Typical uses of straight-line objects are the same as for polylines; that is, to define linear features, such as rivers and boundary conditions at the edges of the model. Straight-line objects are more frequently used in purely hypothetical models where the model is kept very simple rather than in models of actual systems.