2004

300 | Chapter 16 Draw Geometric Objects
Use meshes if you need hiding, shading, and rendering capabilities that
wireframes don’t provide but do not need the physical properties that solids
provide (mass, weight, center of gravity, and so on). Meshes are also useful if
you want to create geometry with unusual mesh patterns, such as a 3D topo-
graphical model of mountainous terrain.
A mesh can be open or closed. A mesh is open in a given direction if the
start and end edges of the mesh do not touch, as shown in the following
illustrations.
AutoCAD provides several methods for creating meshes. You can enter the
mesh parameters manually or use the
3D command, which simplifies the
process of creating the basic surface shapes.
Create a Predefined 3D Surface Mesh
The
3D command creates the following 3D shapes: boxes, cones, dishes,
domes, meshes, pyramids, spheres, tori (donuts), and wedges. These are
meshes that are displayed as wireframes until you use
HIDE, RENDER, or
SHADEMODE.
To view the objects you are creating with the
3D command more clearly, set
a viewing direction with
3DORBIT, DVIEW, or VPOINT. The procedures for
creating 3D shapes are similar to those for creating 3D solids. For more infor-
mation, see “Create 3D Solids” on page 308.
In the following illustrations, the numbers indicate points you specify to
create the mesh.
M open
N open
M closed
N open
M open
N closed
M closed
N closed