Don Morgan II shares with us his method of creating reference lines to align 3D objects in AutoCAD.
"My favorite and most-used tip for working in 3D AutoCAD is using a linear dimension as a reference when moving solids around. When I need to get two solids into a correct position relative to each other — for example, when placing a round sphere into the center of a cube — I will place a linear dimension from the center of the sphere to the center of the cube, and then move the sphere into position by snapping to the end points of the dimension lines.
"I know there are other ways to accomplish this; however, I have found this method very useful for complicated parts that sometimes do not offer a good Osnap reference point, like 'center' or 'midpoint.'"
Notes from Cadalyst Tip Patrol: It is difficult to move 3D objects around in a 2D environment (such as our computer screens) and know where your objects are in space. Having extra linear objects to snap to can be helpful. In Don's example, you can draw a line from one corner of the cube to the opposite corner. This will allow you to snap to the line's midpoint to get the center of the cube. Not all shapes are perfect cubes, so you might have to get creative. You can create a construction line layer to draw these lines on so you can erase them more easily, or just turn that layer off.