There is one thing for certain in the world of AutoCAD®. All users—seasoned veterans and brand new users—had a beginning. Getting back to our roots, there are many basic tools we can use to help us create some custom 3D objects. Let’s go over a few solid editing techniques that will either launch your AutoCAD career or brush up on those old skills. Let’s see what the Union, Subtract, Intersect, Extrude Faces, Slice, and Shell commands have to offer us.
Let’s start by going over some basic 3D modeling techniques. Union, Subtract, and Intersect are the three common commands used when creating custom 3D models. You can find these tools either by typing in their full name in the command line, by using their out-of-the-box shortcuts, or by creating your own custom commands. The out-of-the box shortcut commands are Union = UN, Subtract = SU, and Intersect = IN.
Start by drawing a 3D box with these properties: Length = 12”, Width = 12”, and Height = 12”. Also, draw a cylinder with these properties: Diameter = 6” and Height = 24”. Then take the base of the cylinder and place it on top of the box, directly in the center. Now perform the Union command and select both the box and the cylinder. As you will see, you now have a 3D solid object that is the combination of the cylinder and the box. If you press and hold CTRL, you can use the “filter select” command to select the box or cylinder if you want to change the properties of that object while it is still in its combined form. Give it a try. Hold CTRL down and select the box. Change the length of it to 24” and then exit out. You still have your single 3D solid but the shape of the box has the 24” length property. This filter selecting technique comes in very handy when creating 3D objects when you want to change properties of basic shapes versus starting over again.
Let’s work with the Subtract command now. Once again, create a box and cylinder with the same properties as the ones we created for the Union command. Now, place the center of the cylinder directly in the center of the box overall. Using the Subtract command, select the box first, hit enter, select the cylinder second, and then hit enter again. You have just taken the part of the cylinder that passes through the box and subtracted it from the box, leaving a void. Using the filter selection technique from before, you can still change the properties of each entity without having to start over with your 3D object.
Now on to the Intersect command. Create a box and cylinder with the same properties as you did in the Subtract section and place the cylinder in the same location. Now, perform the Intersect command and select both the box and cylinder. Finishes by hitting enter and you will see that the new shape will be where the box and cylinder intersect, erasing anything else that does not. As before, you can use the filter selection technique to select each original entity and change their properties to update your new 3D object.
With enough practice, these three commands can help create any custom 3D object you want. Using the filter selection technique allows you to change the properties/position of the 3D entity you used to create the custom objects without having to redo/start over. Try using them and see what kinds of custom things you can come up with. Over time, these will become second nature and there will be no limit on what you can create.
Another really helpful 3D editing tool is the Slice tool. With Slice, you can take 3D objects and slice them in different ways and angles to create new 3D objects. To use the Slice command, you can either type it out in the command box, use the out of the box shortcut (slice = SL), or create your own.
Start by drawing a 3D box with these properties: Length = 12”, Width = 12”, and Height = 12”. Now type Slice in the command box and select the 3D box that you created. Select the lower left-hand corner of the box and then select the upper right-hand corner of the box. Before you hit enter, look at the command line. It will give you the option to either keep both sides of the object or to select a point on the desired side of the object to keep. For now, keep it at both. Hit enter to complete the command and you will now have two separate 3D objects in the form of a 3D triangle.
There are a few different ways to use the Slice tool. The previous way described is the most common way to use it in 3D editing. If you perform Slice and select your object, you can look down at your command bar and see the various ways you could slice your 3D object. For example, slice in the XY axis, YZ axis, ZX axis. Let’s do a few different examples of this. Start with your original box as before. Perform the Slice command and select your box. In the command box type in “ZX” and then hit enter. Select the center point on the left side of the box and then the center point on the right side of the box. Hit enter to keep both sides. As you can see, you have a slice right down the middle of the box from left to right. If you were to use the “ZX” Slice command and then select two points in the YZ axis, the slice command will not perform. Once again, create a box as before and this time slice it using the “YZ” command. As you can see, you will have to select points in the Y and Z axis in order for this to work.
With the Slice command, you can further edit your custom 3D object by slicing it in various different ways. This becomes useful when you want to slice the object into two different parts, but want to keep the same shape of the original object just beyond the slice point, or if you want to delete just one side of the object.
Extrude Faces is a useful tool when you want to take a face of a 3D object and extrude it to a specific value. You can even apply a taper to the face that you want. Let’s try it.
Create a 3D box with these properties: Length = 24”, Width = 24”, and Height = 24”and then type “SOLIDEDIT” into the command box. Then type “F” into the command box and hit enter. This will give you the option to select one of the faces of the box. Type in “E” to select the extrude faces command and then select the right face of the box (make sure you are in an isometric view). In the command box, type in 18” to specify the distance in which the face will be extruded and hit enter. The command box will now prompt you to add a taper into the face, but for now just leave it at 0. Hit enter again to complete the command and you will see your face of the box will now grow by 18”.
With the Extrude Faces tool, you can take one or more faces and extrude them with a specific distance that you specify. This comes in handy when dealing with more complex objects that have multiple faces when you just want to extrude one face without affecting any other face on the object.
The Shell command is a useful tool that will take a 3D object and hollow it out to a determined thickness specified by you. Let’s try a few examples.
Create a 3D box with these properties: Length = 12”, Width = 12”, and Height = 12”and then type “SOLIDEDIT” into the command box. Then type “B” into the command box and hit enter. This will give you the option to select the body of the box. Type in “S” to select the Shell command and then select the box. Hit enter and then give your “shell offset distance” a distance of 1”. Hit enter to complete the command and what you will see is that your box now has been hollowed out with a thickness of 1”.
You could bypass typing “SOLIDEDIT” by selecting your Shell command off the Tool ribbon in the Solids Editing menu. If you wanted to remove one or more faces of the box while performing the shell command, all you have to do is select one or more faces when prompted and then that face selected will be deleted from the shell command. Let’s try an example of this.
Perform the Shell command as described earlier all the way up to selecting the box, but do not hit enter after selecting the box. If you look down into your command box, you will see it prompt you to remove faces. Make sure your view is isometric and select the upper face of the box. If the command removed the faces successfully, the command box will display this message – “1 face found, 1 removed.” Now hit enter to give your box a “shell offset distance” of 1” and to complete the command. You will see that your box now has been hollowed out with a thickness of 1” and the top of the box has been removed, creating an open box.
You can use this tool to create hollow 3D objects that are either closed completely or have one/more faces removed creating an open 3D object.
These are some of the basic editing tools you will encounter when editing 3D objects in AutoCAD. By using the Union, Subtract, and Intersect commands, you can work with multiple 3D objects to combine, subtract, or take a combination of the two objects, resulting in a newly created object. The Slice command allows you to edit your 3D object further by slicing it in different angles/ways. With the Extrude Faces tool, you can select one or more faces to extrude out without affecting other faces of the object. You can even add a taper to the face of the object. Once you have your 3D object or even just a part of it, you can use the shell command to hollow it out with a pre-determined thickness. As I stated before, with practice you can use these basic commands to make some very advanced custom 3D objects.