CAD instructor Lewis Skiles presents us with a tip inspired by a comment on Cadalyst Tip No. 3712, "2D Operations in a 3D World," using 3D objects in AutoCAD.
"Someone made a tongue-in-cheek comment about a tip concerning working with 3D vs. 2D in AutoCAD: 'What I really need is a 4D option to allow me to go back in time and correct my mistakes.' Well, you can go back in time, in a way. When modeling 3D solids in AutoCAD, if you find that you made an error when you placed one 3D solid into another 3D solid and used any Boolean operation (Subtract, Intersect, or Union), you can still modify the original if the system variable SolidHist is set to 1, which is the default.
"Select the 3D solid and right-click to choose Properties. Under Solid History, change the value of Show History to Yes. You will then be able to see the 3D solid that was used to modify the original. Hold down the Ctrl key and select the 3D object. You can then move, scale, rotate, or whatever is necessary to achieve your desired result. Then go back to Properties and reset Show History to No. This works even if you have saved and closed the drawing and reopened it."
Notes from Cadalyst Tip Patrol: I always thought working with solids in AutoCAD was difficult — until I learned of this history setting. As long as it's turned on, AutoCAD remembers the solids you used to edit other solids. Even if Show History is turned off, you can still make edits. Press the Ctrl key while selecting the solid and the history object will be displayed, but just the one that was selected. This will allow you to grip-edit the historical object quite easily.