Arbortext IsoDraw > User's Reference > Palette Window Toolbox > Parallel Paths > Blend Tool
  
Blend Tool
You can use the blend tool (Blending of two Bézier paths) to generate elements between two Bèzier paths, the form and fill of these elements being blended from one path to another.
To do this, select the blend tool from the toolbox. The cursor becomes an arrow tip (1) cursor. Click the end point of one path. The cursor changes to an arrow tip (2) cursor. Now click the end point of the second path.
The following dialog box appears:
Use this window to enter the number of intermediate steps you want to generate. Confirm with OK to generate the elements.
In this case, only the form of the elements changes. If the paths have fills, you can generate interesting graphical effects.
Draw two circles as shown in the illustration and convert them into Bèzier paths. Select both paths and choose No pen from the Pens window in order to remove the contour. Now set the fill for the large circle to black in the Fills window. Select white for the small path.
Select the blend tool (Blending of two Bézier paths) from the toolbox and click the marked points one after the other. Enter 100 for the number.