508
AutoCAD and Its Applications—Advanced
Copyright Goodheart-Willcox Co., Inc.
However, these settings are merely a starting point. You will likely spend some time
adjusting lighting to produce the desired results. In some cases, it may take longer to
light the scene than it did to model it.
PROFESSIONAL TIP PROFESSIONAL TIP
If you render a scene and the image appears black, all of the lights
may have been turned off or have their intensity set to zero. A scene
with no lights placed in it will be rendered with default lighting.
Shadows Shadows
Shadows are critical to the realism of a rendered 3D model. A model without
shadows appears obviously fake. On the other hand, a model with realistic materials
and shadows may be hard to recognize as computer generated. In AutoCAD, the sun,
distant lights, point lights, spotlights, and weblights may all cast shadows. AutoCAD’s
default lighting does not cast shadows. There are two types of shadows that AutoCAD
can create: shadow mapped and raytrace. The
Advanced Render Settings
palette
provides settings for controlling the creation of shadows when rendering. This palette
and its options are discussed in the next chapter.
The options for creating shadows are the same for all lights. The options can be
set when the light is created or adjusted later using the
Properties
palette. In the case
of sunlight, the
Sun Properties
palette is used to set the options.
Shadow-Mapped Shadow Settings
A shadow-mapped shadow is a bitmap generated by AutoCAD. A shadow map
has soft edges that can be adjusted. Creating shadow-mapped shadows is the only way
to produce a soft-edge shadow. However, shadow maps do not transmit object color
from transparent objects onto the surfaces behind the object. Figure 17-21 shows the
difference between shadow-mapped shadows and raytraced shadows.
To specify shadow-mapped shadows and set the quality, or resolution, of the shadow,
select the light and open the
Properties
palette (or
Sun Properties
palette). At the bottom
of the
Properties
palette is the
Rendered Shadow Details
category, Figure 17-22. To
specify shadow-mapped shadows, set the
Type
property to
Soft (shadow
map).
Figure 17-21.
The shadow from
the object in the
foreground is a
shadow-mapped
shadow. The shadow
from the object in
the background is a
raytraced shadow.