I am amazed at what the 'Master' masons designed and built during the middle ages with mostly only a square and compass to hand and a good grasp of geometry principles and of course the Romans before them.
Today we have a wonderful 2D cad program - QCAD , in which we can adopt these very same geometry principles and draw equally amazing designs in the fields of Engineering, Construction and design and the probably un-ending list of craft activities.
Outlined below is one method of using QCAD to draw up a simple Gothic Rose window design.
1. Draw a Hexagon, call the Polygon tool;
Line Tools > Polygon and select either polygon (Center point PG1) or Polygon (Two corners PG2).
Enter 6 in the Corner field.
2. Divide Hexagon into 12 equal parts, set up a new layer to do this (Layer Construction, color Magenta).
3. Draw Circle ( circumscribe -outside) using one of the Hexagon corner points for a radii reference.
4. Extend all construction lines to meet Circle circumference.
5. Draw 2nd smaller Circle from center point.
6. Split smaller Circle into 24 equal parts:
Select Circle > Modify > Split Entities - enter 24 in the Parts field and tick the Green tick to finish the process.
7. Draw smaller Circle to fit perfectly between center (End part 'A') and intersection 'B'.
8. Copy and paste Circles to fit (7).
9. Draw a border Circle (8).
10. Repeat process to draw another larger Rosette. (9).
11. Finally 'clean up' the drawing using modify tools - 'Break out segment' and the Delete tool.
* Change the construction layer to a color that suits!
Should be job done .