Q: Can I draw tangents to circles in EXPERT?

A: Expert supports several options for drawing sophisticated shapes. There are three ways to accomplish this task.

(1) If your circles are of the same radius, you may draw a single-segment wire with end style set to ROUND. In addition, you may convert the wire to polygon.

(2) For drawing any types of circles connected by common tangents, try Rolled Region creation (program must be in all-angle mode). In this mode one can create complicated forms consisting of lines and circular arcs. However, you could refer to the user manual, Sect. 5.3.4.

(3) You may create any sophisticated shape using xi (eXpert Interface) language, and even parameterize it. Below is a simple example of spiral polygon drawing written in Xi.


  do begin
	seq = {};
	xx0 = x0;  
	yy0 = y0;
 	xx1 = (xx0); yy1 = (yy0);
	SEQ_ADD_LAST(seq, (xx1));
	SEQ_ADD_LAST(seq, (yy1));

	i = 0;
	loop begin
	if (i EQL len) then (leave loop);
	dSQ = sqrt(xx0 * xx0 + yy0 * yy0) ;
	xx1 = xx0 + arc * yy0/dSQ;
	yy1 = yy0 - arc * xx0/dSQ;
	xx2 = xx0 + wid * xx0/dSQ;
	yy2 = yy0 + wid * yy0/dSQ;
	xx0 = xx1;  
	yy0 = yy1;

 	SEQ_ADD_LAST(seq, (xx0));
	SEQ_ADD_LAST(seq, (yy0));
	SEQ_ADD(seq, 1, (xx2));
	SEQ_ADD(seq, 2, (yy2));

        xx2 = xx0 + wid * xx0/dSQ;
        yy2 = yy0 + wid * yy0/dSQ;
        SEQ_ADD(seq, 1, (xx2));
        SEQ_ADD(seq, 2, (yy2));

        polygon (seq);


Q: Could I change the layer of an object?


A: There are three ways to do this:

(1) If you want to do this to a single object, set "Numeric Input" option on, select "Modify" tool and pick the required object. In the Numeric Input panel you will see the drop-down list, where you may select the required layer

(2) If you must put several objects into one layer, you may do the following:

  • select an object (or several objects);
  • make the layer into which you want to move the object active;
  • apply menu command: Select>>Save Selected>>To Layer

This will copy the selected objects into the current layer. (the objects remain selected in the old layer)

  • Delete selected.


(3) A slightly different routine for multiple objects:

  • select an object (or several objects);
  • apply Edit>>Cut command (e.g., using "Cut" button, labeled with scissors);
  • make the layer into which you want to move the object active;
  • apply Edit>>Paste into Layer command.

For multiple objects routine (3) is easier (less mouse clicks). However, when there are many objects, it is executed slower since it takes some time to copy objects into buffer.

A key advantage of routine (3) is that it allows the user to copy between windows, or between cells.