Join Scott Onstott for an in-depth discussion in this video Creating closed polylines with boundaries, part of 3D Architectural Modeling with AutoCAD.
- In this video we're going to create a series of closed polylines that represent the first floor walls. Let's zoom in on the first floor, and let's turn off certain layers. Use the Lay Off command and click on the interior partitions, the furniture, the doors, the roof, the stairs, the railing, the headers and press enter. So we've reduced a lot of the clutter, and we can focus in on the system in question, which is the walls.
Right now the walls are made of individual line segments, in order to create a 3D model out of this it's necessary to first create closed polylines, and we'll use a specialized command to assist in this process, called Boundary. But first let's create a new layer. Go to the Layer Manager, create a new layer and call it 3D-Walls. You don't have to follow an official layer standard when you're creating a 3D model, these layers are just for your own information, to keep you organized.
I'm going to change the color to red, and set this layer current. When you preface the 3D layers with the letters 3D- they automatically get alphabetized, here at the top of the list, because AutoCAD puts the numbers in front of any letters. I'm going to zoom in over here, in this corner of the building, and then I'll type boundary, bo is the shortcut, enter. This command can either create a polyline or a region, and either would be acceptable for a 3D model.
Polylines are a bit simpler, so I'm going to create them. If you have areas that are composed of splines, then it will not let you create polylines, you'll have to create a region. In this case we just have a bunch of lines, so polylines are ideal. Now click the Pick Points button to pick an internal point within the walls, so I'm going to click right here and what happened is AutoCAD analyzed the information on the screen, and it was able to determine a boundary.
It mathematically casts out raise from the point that you picked, and it determines if they can escape from this container, if you will. And if they can't it will automatically create a boundary like that. Press enter and it creates a new object. I'm going to regenerate the drawing by typing r+e+enter. And now we can see that in red. This red object is a closed polyline, suitable for turning in to a 3D model ultimately.
I'll continue creating boundaries here, I'll type b+o+enter. And instead of clicking here, I'm just going to press enter, because this user interface element has the focus, and you can see that little blue element around the button, so that means I just have to press enter, and it will automatically go into this Pick internal point mode. I'll just click in each enclosed area, and it will create boundaries. Now, if I pan the drawing to an area that wasn't on the screen before, and I try to find a boundary there, it's going to tell me that it can't determine it.
The reason for this is that this boundary command analyzes what's on the screen, and that information was off the screen initially. It wasn't able to determine a boundary. But now that it is on the screen, I should be able to use boundary, press enter, enter. Click there and it works. So this is just a particularity about this command and how it works. You have to have the area that you're bounding fully visible on the screen when you first enter the command Boundary.
I'll regenerate so we can see that red information. Now, down here I'm anticipating a problem because of this gap. Let's see what happens. Boundary, enter, enter. I'll click down here, and it's going to give us an error. It says, "A closed boundary cannot be determined. "There might be gaps between the boundary objects." In fact that is the case here, so close, cancel. In this case I have to fix the drawing, and I'll do that by using the Fillet command.
I'll fillet this two lines, with a zero radius to create a sharp corner there. Now, if I use Boundary, enter, enter. It works this time, regen. Gonna zoom out, and if you just visually follow this around, it goes all the way around here, and it goes down here off the screen, so I'm going to have to zoom out more if I'm going to create a boundary there. I'll type b+o+enter, enter, click inside here and it worked.
I'll just keep going, making boundaries, and each one of these is a separate polyline. It's not gonna work up here, so I'm gonna press enter to end the command. Pan, press enter, enter to repeat the command, and go into Pick Points mode, and I'll just go ahead and create these final missing pieces here and then press enter and then type r+e+enter for regen.
- Arranging elevations and sections around a plan
- Rotating objects in 3D
- Extruding walls, interior partitions, and headers
- Building slabs
- Modeling doors, windows, and stairs
- Sculpting terrain
- Creating a second floor
- Building roof surfaces
- Sculpting watertight solids from surfaces
- Modeling a tower