GLLT.EXE Demonstrates Simple Lighting in OpenGL

ID: Q152001

The information in this article applies to:

SUMMARY

The GLLight sample provides a demonstration of how the various light settings effect an OpenGL scene. The initial scene is simply a single white sphere with a single blue light (GL_LIGHT0) shining on it.

You can modify all of the properties of that light as well as the light model characteristics for the scene to observe the visual effect. GLLight does not use multiple lights and does not allow you to change the material properties of the sphere.


MORE INFORMATION

The following file is available for download from the Microsoft Software Library:

~ GLLT.EXE
For additional information about downloading files from the Microsoft Software Library, please see the following article in the Microsoft Knowledge Base:
Q119591 How to Obtain Microsoft Support Files from Online Services


GLLight allows you to experiment with all of the OpenGL lighting capabilities for a single-light scene quickly and easily. These characteristics fall into the following categories seen in the "Settings" dialog box: 

   Characteristics of the Light Source (GL_LIGHT0):

     Position
     Intensity (ambient, diffuse, specular)
     Spotlight Properties (exponent, cutoff)
     Attenuation (constant, linear, quadratic)

   Characteristics of the Lighting Model:

     Global ambient light
     Viewpoint (local or infinite)
     Lighting (one-sided or two-sided)
The initial settings for these characteristics follow the defaults for GL_LIGHT0 with two exceptions: the Position is moved back so as to light the sphere; and the Diffuse Intensity is set to blue.

The material properties of the sphere are left as defaults except for a white Specular reflectance and a medium Shininess setting. You cannot modify the material properties through the UI in this sample.

To demonstrate the effects of one-sided vs. two-sided lighting, there is an option to place a clipping plane through the sphere in order to uncover the inside of it. To see the difference between the inside and outside more clearly, you should move the light some distance along the x or y axes.


REFERENCES

For more information on the above settings and OpenGL in general, please read:

-Neider, Jackie, Tom Davis, and Mason Woo. OpenGL Programming Guide: The Official Guide to Learning OpenGL, Release 1. Reading, MA: Addison-Wesley, ISBN 0-201-63274-8. (This book is also known as the "Red Book".)

For information on Material Properties in OpenGL, please see: The GLBMP Sample "Demonstration of OpenGL Material Property and Printing" in the Microsoft Software Library, and the "Red Book" mentioned above.

Additional query words: kbgraphic kbfile gllt.exe opengl 


Keywords          : kbfile kbgraphic kbNTOS351 kbNTOS400 kbSDKWin32 kbWinOS95 GdiOpenGL 
Version           : WINDOWS:95,98
Platform          : WINDOWS 
Issue type        : kbinfo

Last Reviewed: June 15, 1999