AutoCAD 3D Modeling: Ambient Light
July 6, 2004 Proper illuminating AutoCAD scenes, is an
important step to generate the final photorealistic rendered
image. There are four types of lights available in AutoCAD as
follows:
- Ambient Light: Provides a constant illumination to
all surfaces of models.
- Point Light: Radiates light rays equally in all
directions. It generates a similar effect to a light bulb.
- Spotlight: Radiates light rays along a conical
direction. It generates a similar effect to a car headlight.
- Distant Light: Radiates parallel light rays. It
generates a similar effect to sunlight.
If you do not place a light source other than ambient light
in a scene, AutoCAD uses an automatic over-the-shoulder light to
illuminate models. By installing a point, distance, or spotlight
the over-the-shoulder light disappears.
The following tutorial shows you the effect of ambient light
on a typical model. In the following tutorial no light other
than the ambient light and over-the-shoulder light is
present.
Note that the ambient light does not produce realistic images
by itself. With ambient light, adjoining surfaces are equally
illuminated and are indistinguishable. That's why in most cases
you must keep the intensity of ambient light low or even zero.
If the ambient color of a material is not in effect or set to
black the ambient light does not affect the model at all. In the
following tutorial I use a material that reflects the ambient
light very well.
Note: This tutorial is designed for AutoCAD
2005 though might be applicable to other releases.
1. Download and
then open
r16_ambient_light.dwg. The file contains a 3D solid shown in
a single viewport [Figure 1].
Note: If you are using AutoCAD 2002 or an
earlier release download
r15_ambient_light.dwg.
Figure 1
2. Invoke the
LIGHT command (choose View > Render > Light...). The Light
dialog box appears [Figure 2].
Figure 2
3. The right
side of the dialog box is dedicated to the Ambient light. Drag
the slider to the far left to assign 0 to intensity and turn off
the Ambient light [Figure 3]. You could alternatively type 0 in
Intensity text box. Click OK.
Figure 3
4. Invoke the
RENDER command (choose View > Render > Render). The command
renders the scene [Figure 4].
Figure 4
5. Repeat the
LIGHT command and change the ambient light intensity to 1.00 –
the highest level. Render the scene [Figure 5].
Figure 5
6. You can
assign a color to ambient light. Invoke the LIGHT command. In
Light dialog box click the Index Color button. The Select
Color dialog box appears [Figure 6]. Select Blue from the
index color list. Click OK in both dialog boxes.
Figure 6
7. Render the
scene. The model appears in blue [Figure 7].
Figure 7
8. Close the
drawing without saving.
About the Author
Alireza Parsai is the founder of cadpanel.com. He is a mechanical
engineer with more than 12 years experience with AutoCAD.
Alireza is an Autodesk Authorized Author, the CAD consultant for HiTech, Canada Institute, a contributing editor
for Augiworld magazine, a writer for CAD Digest, and an
instructor for AUGI Training Program. He has written 8 books in
Farsi, 3 booklets in English, and more than 100 articles for
different magazines and newsletters. You can reach Alireza by
phone at +1 (416) 513 1535, by email at
alirezap@htinsititute.com or visit his website
www.cadpanel.com.
|
