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AutoCAD Tutorial

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.

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