407
What Is 3D Modeling?
Any object can be extruded to a particular height by assigning a z-value
to extrude to. Keep in mind that these items extrude from the ground level up
and some objects can’t be designed this way. For example, think about what
you would do if you were designing a 3D model of a 10-foot-high pedestrian
walkway positioned 15 feet over a busy road. If you digitize the bridge’s footprint and extrude it to 10 feet, it would look like a wall in the middle of the
road rather than a bridge over the road. To get around this, you have to apply
an offset, or a z-value, where the initial object is placed before extrusion. In
this case, the digitized polygon representing the bridge would be offset to a
height of 15 feet (placing it well over the road), then extruded to a height of
10 feet (to capture the dimensions of the walkway). Figure 14.3 illustrates
offset a value applied
to objects to move
them off the ground
level.
FIGURE 14.2 A flat
polygon versus an
extruded block. (Source:
© 2011 Google SketchUp)
FIGURE 14.3 An offset
polygon that has been
extruded versus a single
extruded block. (Source:
© 2011 Google SketchUp)