122 Section 1 Introduction to Drafting
hidden-line-removed display. However, to create
a more realistic representation of the 3D objects,
most CAD systems have the ability to shade or
color the model. This is called rendering. Render- g g
ing has traditionally been done by hand with
paint, charcoal, chalk, pencils, and ink. How-
ever, just as the process of creating a drawing
has been automated with CAD, so too has the
process of rendering the drawing. Generally,
there is a
Material
command used to defi and fine
apply surface textures to objects. There is also
typically a
Render
command used to “color”
the drawing. Many high-end CAD programs can
produce very realistic renderings, given enough
“drafting” time to properly set up lights and
materials, Figure 4-24.
Some CAD programs have the ability
to add movement to objects in the drawing
to create an animation. An animation is a
series of still images played sequentially at a
very fast rate, such as 30 frames per second,
Figure 4-25. There are very small differences
between each frame and, when each frame is
viewed quickly, the brain “mistakes” these
differences as movement. Generally, there
is an
Animate
command used to add move-
ment to the objects and a
Render
command to
render the animation.
Figure 4-23. User coordinate systems are commonly used in 3D modeling. For this model, a UCS is established
on the inclined surface to simplify construction of the large hole feature. A—The coordinate system shown is par-
allel to the base of the model and was used to construct the features in the base. B—A UCS is created parallel
to the inclined surface to construct the cylinder (drill object). The origin specified for the UCS is a corner on the
surface. Notice the direction of the XYZ axes. C—The drill object is moved down along the Z axis to the required
depth for removing material. D—The completed model.
Inclined
surface
A
C
B
D
Coordinate
system origin
Y X
Z
UCS
origin
Z
Y
X
Z
Y
X
Drill
object
New UCS
Z
Y
X