Graphics Programs Reference
In-Depth Information
3.
Draw another 3D polyline in the mirror image of the fi rst (see the lower image in
Figure 20.28).
4.
Erase the connecting vertical lines that make up the frame, but keep the rectangles. You'll
use them later.
All objects, with the exception of lines and 3D polylines, are restricted to the plane of your cur-
rent UCS. Two other legacy 3D objects, 3D Faces and 3D meshes, are also restricted. You can use
the Pline command to draw polylines in only one plane, but you can use the 3DPoly command to
create a polyline in three dimensions. 3DPoly objects can't, however, be given thickness or width.
Creating a Curved 3D Surface
Next, you'll draw the seat of the chair. The seat of a butterfl y chair is usually made of canvas,
and it drapes from the four corners of the chair legs. You'll fi rst defi ne the perimeter of the seat
by using arcs, and then you'll use the Loft tool to form the shape of the draped canvas. The Loft
tool creates a surface based on four objects defi ning the edges of that surface. In this example,
you'll use arcs to defi ne the edges of the seat.
To draw the arcs defi ning the seat edges, you must fi rst establish the UCSs in the planes of
those edges. In the previous example, you created a UCS for the side of the chair before you
could draw the legs. In the same way, you must create a UCS defi ning the planes that contain
the edges of the seat.
Because the UCS you want to defi ne isn't orthogonal, you'll need to use the three-point
method. This lets you defi ne the plane of the UCS based on three points:
1.
Click the 3-Point UCS tool from the expanded Coordinates tool group in the Tool Sets pal-
ette. You can also choose Tools
New UCS
3 Point on the menu bar or type
UCS
↵
3
↵.
This option enables you to defi ne a UCS based on three points that you select. Remember,
it helps to think of a UCS as a drawing surface situated on the surface of the object you
want to draw or edit.
2.
At the Specify new origin point <0,0,0>: prompt, use the Endpoint osnap to pick
the bottom of the chair leg to the far left, as shown in the left image of Figure 20.29. This
is the origin point of your new UCS.
3.
At the Specify point on positive portion of X-axis: prompt, use the Endpoint
osnap to pick the bottom of the next leg to the right of the first one, as shown in the left
image in Figure 20.29.
FIGURE 20.29
Defi ning and sav-
ing three UCSs
Y axis
Y axis
X axis
Y axis
X axis
Origin
Origin
Origin
X axis
Set up the Front UCS.
Set up the Side UCS.
Set up the Back UCS.
