The Regen command is used to regenerate the whole drawing from the current viewport.
How to access the command?
From menu: View > Regen, as shown in the following picture,
By entering command: REGEN, as shown in the following picture,
Why use REGEN command ?
The Regen regenerates the entire drawing and recomputes the screen coordinates for all objects. It also re-indexes the drawing database for optimum display and object selection performance.
When to use REGEN command?
We can try to draw a circle and then do a “zoom” with the mouse wheel. We will see at some point, the zoom stops, as shown in the following picture,
Now we can execute the REGEN command to continue to zoom it,
If we execute the REGEN command again, the circle will zoom out again.