Join Kacie Hultgren for an in-depth discussion in this video Drawing on faces, part of Modeling a Staircase with AutoCAD.
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In this video, we'll learn about the various ways to manipulate the UCS and draw on faces. If you've worked in 3D before, you know about the UCS. It's the User Coordinate System. When you draw in 2D, circles, lines, etc... you draw on a plane, and more specifically in AutoCAD, you draw on the XY plane. The UCS tools let us reorient the XY plane by flipping it or aligning it with a face or object. Let me show you how this works.
Let's orbit around and zoom in on our origin. Now, draw a rectangle on the XY plane. REC, we'll start at the origin, and click off in space here. But what if I want to draw a rectangle on this plane? I can't draw on the ZY plane, so I need to reorient. I'll type "UCS" and "y" to rotate around the y-axis. Enter. And then enter a 90 degrees, or accept that default value.
And draw another rectangle. And you can see it's oriented differently. Now, let's rotate the UCS one more time. I'll type "UCS", then "x" > Enter. And then Enter one more time to accept that default 90 degrees. I'll draw one more rectangle. And we can also use the UCS command to return us to the World Coordinate System by typing "w" > Enter.
The ribbon also has a handful of options for orienting the UCS. Let's go to the Home tab. And you can see under the coordinates panel here, we can change this on the drop-down menu. Notice how as I change these different coordinate systems, the UCS icon rotates, the grid rotates with it, but the view doesn't change. Now I'll zoom out and delete those three extra rectangles and return us to the World Coordinate System.
So what we want to do is draw on the front face of the step. Let's orbit around and take a look at it. Now, unfortunately the front face of our step doesn't actually align to any of the standard orthographic views or coordinates in AutoCAD, and so we're going to need to make our own. This is where the dynamic UCS can actually come in pretty handy. Let's turn it on down here on the status bar. Get just a little bit better view here. I'll invoke the polyline command, and as I mouse over this face, note that it highlights, and I can drop points anywhere I want.
Click "Enter" to close it, and that polyline is aligned with the face of our step. Let's delete that test line. Now, this works really great in a lot of situations, but sometimes it can be a little tricky to be accurate, especially if you want to use tracking points or have more complex geometry, and so in these cases, sometimes it can be better to turn off that dynamic UCS. Let's do that now. And manually change the UCS instead. Ah, one of the easiest ways to that is actually to just drag on the points of our UCS icon, and align them to our shape.
So now I have our XY plane aligned with the face of our front step. So our UCS is correctly aligned to draw on this face. Now we'll create 2D line work on the face of the step so that we can use it to refine the 3D solid. For visual clarity, I want to change up the color of my lines, and to do so I'm going to get the properties palette more visible. Type in "properties" into the command line, and this is already docked here on the side which is going to be convenient for me later.
I'm going to change the current color to red, and hide this here. I'm going to use the polyline command. I'll hover on this corner and then use polar tracking, kind of drag out to the side, type "2 inches" to start my polyline. Notice those dotted lines? Those are polar tracking lines and they help us kind of make sure that we're drawing at the correct angle even if we're looking at a view obliquely.
Let's type "7">Enter. Then, off to the side here, "25">Enter. Back down, click to that intersection, and we can type "c">Enter to close that shape. Now, let's also create some circles. We'll start the origin on those end points. Use a radius of two, and do the same on the other side. Then, let's use the trim command. Now I want to do a little bit more work with these lines, and I actually find that it's usually easier to switch to 2D wireframe when you want to work with 2D objects, even if it can be a little bit visually confusing.
So, we'll switch that visual style now. I'm going to use the trim command "TR". You can also find it up here under the Modify panel. I'll select both circles and that rectangle. Click Enter, and then trim away the geometry that I don't want. I'll click Enter. Then I'll use the Join command. Select those lines and click Enter.
Then I can extrude this 2D shape. We can invoke that from the ribbon. Click on our 2D shape and let's make it one inch deep. Now we'll use the Boolean subtraction tool to subtract the red shape from the green shape. We can use subtract in the command line. You can also find the Boolean options under the solid editing menu. First, I'll select the green shape. Enter.
Then the green shape. Enter. And you can see that our step now has a profile on the front. Now, that looks pretty good, but there's actually an even more efficient way to tackle this, so I'm actually going to step back a few steps. We'll use Ctrl-Z to step back until we have our 2D geometry. Now, there's a tool called Presspull, and it's located up here next to the Extrude tool. As we mouse over, you can see that it selects this sort of bounded area.
We can click inside it and pull backwards, and we'll type "1">Enter, for one inch. And then hit return to exit out of the command, and you can see we actually end up with the exact same result with about four less steps. Let's delete those excess 2D lines. Hit "E">Return. And now we're done. So let's move on to the next step.