AutoCAD changing shapes...

Often when I draw something in AutoCAD - say an arc or spline for example - often when I come back to it later it will appear on the screen as a straight (or a series of straight) lines.
If you click on it, the control points are in the correct place, but the 'line' isn't.
Can anyone tell me how to prevent or correct this?

 

Autocad uses a coarse polyline-approximation when drawing arcs and splines to keep drawing up to speed. This has nothing to do with the internal representation of the curves. Simply type "regen" to force Autocad to draw the line more accurate and you'll see that your curve is still correct.

 

Merci!

 

You can also type VIEWRES and set that system variable to a higher value, I suggest 1000 or 2000:

Command: VIEWRES
Do you want fast zooms? [Yes/No] <Y>: Y
Enter circle zoom percent (1-20000) <1000>: 2000