Tipster Greg Silva demonstrates how he uses point filters when drawing in three dimensions.
"Point filters have been in AutoCAD for a very long time. If you are currently working in 3D then you already know that AutoCAD's coordinate system is x, y, and z, in that order. Point filters can grab part of a coordinate and build a new one.
"Let's say you want to insert a circle at a center elevation above another circle that happens to be at the coordinates (6.0, 2.0, 12.25). That is 6.0 in the x and 2.0 in the y and 12.25 in the z elevation. Start the Circle command by typing Circle at the command line, or select from one of the command icons found in many locations on the AutoCAD menu, toolbar, or ribbon. For the insertion point, type in .XY and press Enter. Next, select the point that you would like to obtain the x and y coordinates from; in this case, it would be the center of our existing circle. AutoCAD will prompt you for the needed z value. You can type in your new elevation or select something that is already in that elevation, and AutoCAD will apply that to the x and y you have already obtained to create a new point, drawing your circle at that location."
Notes from Cadalyst Tip Patrol: Working in 3D can be very frustrating because when we work in a 3D file, we are still working on a 2D screen. Interpreting the data visually is often awkward. Point filters can be very helpful, ensuring you are working on the proper plane. There are several point filters available: x, y, z, xy, xz, and yz. You can type these in to access them with a decimal first, and then the filter, or you can use the shortcut menu: Shift + right-click. Click on the point filters option, and then select the filter you want to use. Don't limit their use to 3D modeling; you can use them for 2D layouts and drafting