Rectangles are a special case of polygons that have four edges that are parallel to the grid. (With SUTRA models, straight lines are oriented parallel to X, Y or Z axes.) To create a rectangle, the user does the following:

1.The user either selects Object|Create|Rectangle or clicks on the Create rectangle object button .

2.The user moves the cursor to the location on one of the views of the model where the first vertex of the rectangle object is desired.

3.The user clicks the mouse button again at the opposite corner of the rectangle. 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 rectangle objects are the same as for polygons; that is, to define zones with differing media properties. Rectangle objects are more frequently used in purely hypothetical models rather than in models of actual systems.