30
AutoCAD and Its Applications—Advanced
3D Construction Techniques 3D Construction Techniques
Before constructing a 3D model, you should determine the purpose of your
design. What will the model be used for—manufacturing, analysis, or presentation?
This helps you determine which tools you should use to construct and display the
model. Three-dimensional objects can be drawn as solids, meshes, or surfaces and
displayed in wireframe, hidden-line removed, and shaded views.
A wireframe object, or model, is an object constructed of lines in 3D space. t
Wireframe models are hard to visualize because it is diffi to determine the angle ficult
of view and the nature of the surfaces represented by the lines. The
HIDE
command
has no effect on a true wireframe model because there is nothing to hide. All lines are
always visible because there are no surfaces or faces between the lines. True wireframe
models have very limited applications.
Surface modeling represents solid objects by creating a skin in the shape of the g
object. However, there is nothing inside of the object. Think of a surface model as a
balloon filled with air. A surface model looks more like the real object than a wire- fi
frame and can be used for rendering. Surface models are often constructed for applica-
tions such as civil engineering terrain modeling, automobile body design, sheet metal
design and fabrication, and animation. Surface modeling techniques are discussed in
Chapter 10.
Like surface modeling, solid modeling represents the shape of objects, but it g
also provides data related to the physical properties of the objects. Solid models can
be analyzed to determine mass, volume, moments of inertia, and centroid. A solid
model is not just a skin, it represents a solid object. Some third-party programs allow
you to perform finite element analysis (FEA) on the model. Solid model files fi can also fi
be exported for use in stereolithography, rapid prototyping, and 3D printing. These
processes can produce a plastic or polymer prototype for analysis and testing. This is
discussed in Chapter 14. In addition, solid models can be rendered. Most 3D objects
are created as solid models.
In AutoCAD, solid models can be created from primitives. Primitives are basic
shapes used as the foundation to create complex shapes. Some of these basic shapes
include boxes, cylinders, spheres, and cones. Detailed shapes and primitives can be
created using 3D mesh primitives, mesh modeling techniques, and surface modeling.
Figure 1-17.
The rendered model is displayed in the
Render
window.
Rendered
image
Renderings
completed in
this drawing
session
Information
about the
rendering