Graphics Programs Reference
In-Depth Information
Presspull works with any closed 2D shape, such as a circle, closed polyline, or other com-
pletely enclosed area. An existing 3D solid isn't needed. For example, you can draw two concen-
tric circles without the 3D box and then use Presspull to convert the circles into a 3D solid ring.
In the previous exercise, the solid box showed that you can use Presspull to subtract a shape
from an existing solid.
As you saw in this exercise, the Presspull command can help you quickly subtract a
shape from an existing 3D solid. Figure 19.18 shows some other examples of how you can use
Presspull. For example, you can draw a line from one edge to another and then use Presspull to
extrude the resulting triangular shape. You can also draw concentric shapes and extrude them;
you can even use offset spline curves to add a trough to a solid.
FIGURE 19.18
Adding complex
shapes using the
Presspull com-
mand
DRAWING OUTSIDE THE SURFACE
If you use an open 2D object such as a curved spline or line on a 3D surface, the endpoints must
touch exactly on the edge of the surface before Presspull will work.
Making Changes to Your Solid
When you're creating a 3D model, you'll hardly ever get the shape right the first time. Suppose
you decide that you need to modify the shape you've created so far by moving the hole from
the center of the box to a corner. The next exercise will show you how you can gain access to the
individual components of a 3D solid to make changes.
The model you've been working with is composed of two objects: a box and a cylinder
formed from two circles. These two components of the solid are referred to as subobjects of
 
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