This is a special type of 3D Drawing mode which is available only for graphics hardware supporting OpenGL quad-buffered stereo. In this mode, left- and right-eye images are drawn and displayed by either of two methods:
1) Shutter glasses. The images are drawn independently and flashed alternately on the screen at a high rate - 120 times per second in the latest computer implementations, for example those supported by the nVidia Quadro series of display cards. A special monitor is required, and it must be viewed with special shutter glasses which blank out the left and right eyes alternately in synch with the images on the screen.
2) Polarized monitors or projections. The monitor or projector simultaneously or alternately (very rapidly) generates two images which are polarized at 90 degrees to each other, or with different circular polarizations. Some "3D" (stereoscopic) televisions have different polarizations (and different images) for alternate lines on the screen and some projectors and TV's use a checkerboard pattern. Theater 3D systems use this method. It does not require expensive shutter glasses, only relatively cheap polarizing glasses for each viewer.
See the Stereoscopic Display section in Reference for general requirements and procedures.
Two settings affect the perception of depth in stereo viewing:
1) The Stereopair Rotation Angle, set in a dialog in the Input2 Men, or in the DialogBar - Right. A value of about 1 to 3 degrees is usually appropriate (smaller when starting out in stereo viewing).
2) The Perspective distance which is set in a dialog in the Input2 Menu, or in the DialogBar - Right. A value of about 100 Angstroms is usually appropriate, but it may be smaller for small structures.
In viewing real life objects setting the perspective distance would fix the stereopair rotation angle because the human eyes are a fixed distance apart. However in viewing objects on an Angstrom scale the interocular distance is arbitrary, and thus it is possible to set both parameters - in effect the stereopair rotation angle fixes the interocular distance or the scale of the atomic structure relative to the viewer.
Not all stereo hardware supports OpenGL. The GeForce series of video cards from nVidia supports stereo viewing with shutter glasses, but only through the Windows 3D system software, Direct3D, for which a different drawing mode is available in SHAPE. Direct3D is only available on Windows systems, not Macintosh or Linux. Although hardware is indifferent to whether the program draws in 3D through OpenGL double-buffered, OpenGL quad-buffered or Direct3D, the proper driver software must be present. Polarizing monitors may or may not have drivers supporting OpenGL.
Older stereo drawing drivers from nVidia, which worked only on Cathode-Ray-Tube monitors, not flat-screen LCD monitors, supported OpenGL without quad-buffering, as well as Direct3D. This system worked with inexpensive shutter glasses, but if the refresh rate of the monitor is less than 100 hz or so the flicker tends to be excessive. If you are using such a system, you do not need to select the SHAPE 3D Quad Stereo Mode; stereo images can be viewed in the OpenGL Single Drawing mode. However, stereo will be shown only in Fullscreen display. The stereo effect is turned on with a hot key or other switch for the hardware.
Stereo viewing works best when Perspective is selected.
Certain high-end nVidia Quadro cards support quad stereo on Linux, using special "Professional" emitters and glasses. This mode is thus available in Linux, although it will not produce stereo images without this special hardware. This mode has not been tested on Linux.
Setting up nVidia 3D Vision for quad-buffered OpenGL. In the nVidia control panel, select Manage 3D Settings in 3D Settings. In the Global Settings tabe, the Global presets option can be set to "3D OpenGL Stereo". It may then be necessary to select the particular setting Stereo - Display Mode and set it to "Generic active stereo (with NVIDIA 3D Vision)".
If you have a recent Vidia Quadro card it may support 3D Vision stereo through Direct3D as well as OpenGL. There seems to be no advantage to using Direct3D if quad-buffered OpenGL is available, but if Direct3D is used, different settings may need to be selected in the nVidia Control Panel. The Global preset option should probably be "3D App - Default Global Settings". All the nVidia settings may change and it may be necessary to experiment to find the best combination.
Not all stereo hardware supports OpenGL. The GeForce series of video cards from nVidia supports stereo viewing with shutter glasses, but only through the Windows 3D system software, Direct3D, for which a different drawing mode is available in SHAPE. Direct3D is only available on Windows systems, not Macintosh or Linux. Although hardware is indifferent to whether the program draws in 3D through OpenGL double-buffered, OpenGL quad-buffered or Direct3D, the proper driver software must be present. Polarized monitors may or may not have drivers supporting OpenGL.
Older stereo drawing drivers from nVidia, which worked only on Cathode-Ray-Tube monitors, not flat-screen LCD monitors, supported OpenGL without quad-buffering. This system worked with inexpensive shutter glasses, but if the refresh rate of the monitor is less than 100 hz or so the flicker tends to be excessive. If you are using such a system, you do not need to select the SHAPE 3D Quad Stereo Mode; stereo images can be viewed in the 3D Single Drawing mode. However, stereo will be shown only in Fullscreen display. The stereo effect is turned on with a hot key or other switch for the hardware.
Stereo viewing works best when Perspective is selected.
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Setting up nVidia 3D Vision for quad-buffered OpenGL. In the nVidia control panel, select Manage 3D Settings in 3D Settings. In the Global Settings tabe, the Global presets option can be set to "3D OpenGL Stereo". It may then be necessary to select the particular setting Stereo - Display Mode and set it to "Generic active stereo (with NVIDIA 3D Vision)".