Centre or Focus Position

This form of construction derives a position as the center of a specified circle, arc, ellipse, rectangle, hexagon, table, diamond or equilateral triangle. A point may also be constructed using the focus of an ellipse.

Example

1. NEW STRA

   FPT X150 Y250

   TPT CEN OF @

   (or NEW STRA DEF X150 Y250 CEN OF @)

   Here, the line has one of its endpoints defined explicitly, the other as the center of the element (in this case a circle) hit by the cursor.

   

   Figure 20:7. Use of the CENTRE Construction

2. NEW TEXP text DEF CENTRE PREV CIRCLE

   Here, the text origin is placed at the centre of the previous circle element in list order.

3. NEW STRA

   FPT @

   TPT FOC OF /ELLI1 QUAL @

   Here, the ‘to’ point of the line is placed at the focus of ellipse /ELLI1 qualified by a cursor hit.

   

   Figure 20:8. Use of the FOCUS Construction