[Terry Capps]

Thanks for the quick reply, Andy.

I often model small real-world objects by inserting vertices at precise locations, building surfaces from them, and sometimes extruding surfaces. Occasionally, I had noticed that the object location (as specified by the Object Properties Editor) didn't seem right, but hadn't given it much thought until now.

The location specified by the Object Properties Editor is fine for simple objects (like boxes, spheres, or cylinders), but if you start with a surface and extrude it, ac3d keeps track of where the original location of the surface was (this is what shows in the Object Properties Editor) and then specs the location of each of the object vertices in respect to that original location.

If you select the object in object mode and then click on "Object, Re-centre", the location of the object (as shown in the Object Property Editor) will be corrected. If you have the Object Property Editor displayed, nothing will happen until you re-request it (F9).