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## Stereoscopic Liquid Crystal Shutter Glasses

Stereoscopic liquid crystal (LC) shutter glasses are a cheap, easy solution for getting real 3D stereoscopic imaging out of a standard PC with any standard monitor. LC shutter glasses work by constantly blanking out video information for each eye in a sequential fashion, allowing the user to see the left image for a fraction of a second followed by the right image, followed by the left image again etc. In order to make LC shutter glasses work effectively on PC based graphics controllers, some mechanism for changing the displayed video information at every vertical retrace is necessary. New hardware is available that will do this automatically, and the graphics device driver defines the software interface necessary to allow applications to use these new hardware features.

The steps involved in enabling free running stereoscopic support are as follows:

1. Set the mode via SetVideoMode (using a high refresh rate if possible, such as 120Hz to 150Hz).

2. Enable free running stereoscopic mode by calling EnableStereoMode with a value of TRUE.

3. Draw the images for both the left and right eye images by using the SetDrawBuffer function to draw the left and right eye buffers (either side by side or above/below formats will work). Once both left and right eye images are rendered, the visible display buffer can be swapped as per normal using the SetStereoDisplayStart function. This function takes the byte offset of the left and right images as parameters, and the hardware will automatically flip between the left and right eye images at every vertical retrace.

4. To temporarily disable stereoscopic rendering, call the SetStereoDisplayStart function with both the left and right start addresses set to the same buffer. Although the hardware will still be in stereo mode, the screen image will not change every vertical retrace period.

5. Disable free running stereoscopic mode by calling EnableStereoMode with a value of FALSE when you are done with stereoscopic viewing.

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