Active Display Devices

Active devices, such as LCD shutter glasses, time-multiplex a single display device between views for the left and right eye. DirectDraw creates two surfaces that require synchronization to the active device. The active device controls when each eye sees the display, while the system alternately blocks the left and right eye's view of the monitor. Each eye is presented with images at half the refresh rate of the monitor. Consequently, applications should use this stereo view technique only at high refresh rates. Using shutter glasses requires that the monitor support a sufficient refresh rate. Ideally, the refresh rate should be 60 Hz (or greater) to each eye. For more information on refresh rates, see Refresh Rate Enumeration.

For sequential displays, such as shutter glasses, the driver must keep the display synchronized with the active device. Typically, the driver must monitor the state of the active device. For example, the Video Electronics Standards Association (VESA) standard stereo connector can control the shutters of an active LCD device and a driver can monitor which eye is active at a particular time. Based on this information, the surface flip will guarantee that both the left and right images are always presented in pairs to the display.

DirectDraw exposes only those active devices that have a graphics card with a direct stereo connector. Add-in goggles are not supported.