such images require a specialized source as well as additional hardware and software in order to be displayed and interpreted correctly in a typical 3d active stereo viewing environment.
description
in simple terms, images generated from a 3d-video source consist of a series of images (frames or fields) that alternate quickly between two slightly different viewpoints corresponding to the separation of our left and right eyes. when these frames are displayed with enough speed and viewed with special glasses synchronized with the left/right frames, the resulting “single” perceived image appears with much the same depth and perspective we sense in the real world.
how to activate 3d
once you have the necessary source and hardware/software setups described below, the mirage projector will detect and process a stereographic 3d signal automatically.
in addition, if you are using christie’s 3d stereo sync cable (available early 2005), select the appropriate “3d stereo sync” setting in the advanced image settings menu. see 3.8, adjusting the image for more information.
christie’s stereo 3dtm interface module used with earlier mirage 2000/4000/5000/6000 models is not compatible with mirage s+ models.
what 3d sources work?
a stereographic 3d-video signal is sent to the projector via analog cables such as:
1 3-wire rgb sync-on-green
2 4-wire rgb with composite sync
3 5-wire rgb with separate h-sync and v-sync
4 dvi
refer to 2.5, connecting sources for full details and illustrations.
most 3d signal formats currently available are optimized for display via crt (cathode ray tube) technology, thus they have high pixel rates unsuitable for use in mirage. however, by reducing the blanking in these signals, you can lower their pixel rate enough to be compatible with the projector (under 220 mhz). typically, a high-end graphics workstation that includes hardware and software tools for customizing video output timing parameters can produce the requisite 3d signals, as can a pc running windowstm 98/2000 (use the “powerstrip” utility)—consequently your 3d displays should originate from either of these sources, or one that is similar. the silicon graphics onyxtm workstation is an example—it includes video format
compiler software capable of properly modifying “timing” in the signal for use with the projector (it provides a .vfo file). other similar workstations may also provide the special video driver needed.
not all systems include the hardware/software necessary for reconfiguring the 3d video output timing parameters—these sources may not be compatible.
in addition, mirage requires the following conditions for 3d work at these higher frame rates:
3d source requirements and conditions
use a progressive rgb source with native resolution up to 1400 x 1050 (can be cropped if desired). higher resolution can be used, but edge pixels will be cropped rather than the image resized to fit.
92-115 hz input frame rate if sxga+ resolution.
pixel rate must be less than 220 mhz
requires at least 14 lines of vertical blanking
use minimized line rates (horizontal frequency)
3d produces only a single frame delay and limits some ranges for position and resizing (particularly vertical).
hardware requirements
typical hardware configurations for active and passive 3d systems are shown in figure 3.24, figure 3.25, figure 3.26 and figure 3.27. hardware descriptions follow the illustrations.
appropriate 3d source: signals from your 3d source (workstation or pc) must be customized to precisely match the processing capabilities of the projector. in addition, the source must provide a separate synchronization signal that precisely controls when left/right fields are visible through the viewer’s glasses.
1 inverter: your 3d displays will usually require adjustment of frame delay, which can be approximately 1-3 frames set in 1-line increments. if the delay is 1 frame or 3 frames, it needs correction (i.e., reversal of frames), otherwise image data intended for one eye would be delayed and seen by the other—images would lose their 3d quality. if a 3d source cannot invert the signal,thereby synchronizing the left/right shutters in your 3d glasses with the corresponding images displayed by the projector, you can invert via a left/right ttl inverter or by using the 3d stereo sync cable and the proper 3d stereo sync setting in the advanced image settings menu. either configuration ensures that shutter changes in the glasses allow each eye to receive the image data intended for it, regaining the 3d effect in the display. in addition, you can lock the r/l signal to mirage’s output frame sync.
depending on your workstation, you may be able to reverse left/right frames through software only, eliminating the need for separate inverter hardware or the 3d stereo sync cable.
2 ir emitter: in response to an incoming sync signal, this small device emits left/right ir signals to a receiver in active 3d glasses, causing their left/right shutters to alternately open and close for active stereo applications.
connecting one of the 3d stereo sync cable outputs to an emitter also enables you to switch back-and-forth between active and passive systems, if desired.
3 glasses: active glasses differ in speed/performance—consult the documentation for your glasses and keep their specifications in mind when reconfiguring your source signal. the input signal must be optimized for the available shutter speed in order to prevent obvious “ghosting” of image content (known as cross-talk in 3d applications) as well as other more subtle color artifacts. such problems indicate that the eyes are detecting portions of the opposing frame due to an “out-of-sync” system, and can occur in either active or passive 3d configurations.
in the advanced image settings menu, the correct “3d stereo sync delay” setting helps to synchronize glasses with the displayed images. see also customizing the input signal, below, for examples of well-synchronized systems.
in a passive system, where glasses do not have shutters and instead depend on the speed and accuracy of the pi cell polarizer, the input signal must be synchronized with the polarizer.
software requirements
to customize your 3d input signal for use with the projector, you will need access to software that controls video output timing from the graphics source. for example, the video format compiler (vfc) and ir combine are recommended when using the silicon graphics onyxtm workstation.
customizing the input signal
the display must be synchronized with shutter control—called gating—so that each eye receives only the frames of data intended for it, otherwise you will detect opposing data frames (cross-talk) and see faulty images. this requirement means that timing parameters in your source should guarantee the following:
1) each new frame begins after the opposing shutter mechanism is closed
2) each frame completes its display before the opposing shutter mechanism begins to open.
3) each frame (mirror sequence) is displayed in its entirety to the correct eye.
what to adjust
since most current 3d-video sources do not have the necessary characteristics for use with mirage, you must synchronize the projector’s display with your gating mechanism by adjusting the vertical sync width and/or vertical back porch of the input signal and, in many cases, by adjusting the projector’s “dark interval” control. these two parameters—input timing and dark interval—are described below. note that because they interact with each other, you may have to go back and forth between them when optimizing the 3d display.
1) vertical sync width and/or vertical back porch blanking of your input source.
choose the vertical sync width and/or vertical back porch timing to determine when the next field begins displaying relative to the vertical sync signal. the degree of timing adjustment needed depends on the specific signal at hand as well as the performance of your glasses. an example of improvements to poor synchronization is shown in figure 3.28. after adjustment, shutter changes occur during the dark interval between frames.
the example in figure 3.28 assumes that the first active line of your signal is displayed on the first line of the mirage display panel rather than being repositioned higher or lower using the projector’s v-position control.
when using a 3d stereo sync cable at the mirage gpio port, select the dark interval, which 3d stereo sync input (a or b) is connected, adjust the 3d delay, and choose the 3d stereo sync locking/inversion options applicable for your installation:
2) dark interval—(note: not always required). for slower gating technologies, you may also need to artificially increase the amount of dark time between displayed frames so that shutters have even more time to open/close and each eye sees the full display intended for it (figure 3.29b). symptoms are more subtle than cross-talk—if the dark interval is too brief for proper gating, you may notice an apparent color temperature problem, with some whites or grays appearing with a slight red, green or blue tint. this color artifact is particularly easy to diagnose in a grayscale test pattern displayed in 3d mode. in the advanced image settings menu, increase the “dark interval” as necessary until the grayscale is correct—you may also have to increase the internal frame delay when using a longer dark interval. the dark interval range of adjustment depends on the vertical frequency of your source—the higher the frequency, the smaller the range.
1) increasing the dark interval decreases the peak brightness of the image. use only if necessary—you may prefer some color artifacts rather than reduced brightness, or vice versa. 2) higher input frame rates limit the range of dark interval adjustment. 3) faster glasses allow a briefer dark interval.
3) 3d stereo sync—this option defines 1) whether or not the incoming 3d signal locks to the vertical sync output so that signals are synchronized, and 2) whether or not the 3d frames must be inverted, i.e. swapped left-with-right.
the correct setting ensures that the projector’s 3d display of left/right frames is synchronized with other 3d system components so that left/right image data is seen by the intended eye. select the option corresponding to your 3d source connections and timing, and use only if the mirage 3d stereo sync cable is connected between the projector’s gpio port and a server (this cable replaces the need for a separate ttl inverter as described in 3.xx, 3d images). keep this adjustment off (default) when you are not using the 3d stereo sync cable.
with your sync cable, z-screen and, if desired, emitter connected as described in 3.xx, 3d images, select the option suited to your 3d configuration (see above). if frame delay is 2 (or 0), do not invert; if frame delay is 1 or 3, invert. generally, an “unlocked” setting is synchronized with the incoming l/r signal rather than the vertical sync output, and may be needed only with multiprojector installations in which the vertical sync outputs vary slightly.
4) 3d stereo sync select—define which of the mirage 3d stereo sync cable’s input connecters is routed to your server. input a = bnc connector, input b = 3-pin mini-din connector. use only if the cable is present.
5) 3d stereo sync delay—set when the l/r frames begin, defining the best reference point for synchronizing the display with your glasses. proper adjustment should eliminate cross-talk and odd colors caused by timing differences between the glasses and the projected display. use this slidebar only if the mirage 3d stereo sync cable is connected between the projector’s gpio port and a server. slidebar values indicate the number of lines that are delayed.
figure 3.30 shows the various relationships between signals and mirage software adjustments for 3d images.
compatible 3d sources
the following sources are optimized for active 3d images using the projector and active glasses. clamp location is “back porch”. keep in mind that formats beyond those shown below may also be compatible.
3d troubleshooting
refer to the following guide if 3d images image displayed by your projector do not appear as you expect:
flickering image: increase the incoming frame rate as much as possible.
image is compressed horizontally: increase pixel tracking. if already maximized, the pixel clock rate of the source is too high for the projector.
3d cross-talk (ghosting): 1) make sure the ir emitter is not blocked and that its signals can reach glasses. 2) if using a pi cell polarizer and passive glasses, make sure you are using a screen that maintains polarity. 3) are depleted batteries slowing down the active glasses? 4) fix timing parameters in your source. 5) adjust dark interval setting.
no image, jumpy image, or noise at image top: your video card’s minimum timings for blanking and pulse width are too slow for use with the projector.
without glasses, i see only a single image: you are not in 3d mode.
with glasses, perspective appears “reversed”: if vanishing points of objects appear in the foreground rather than background, destroying perspective, the ttl inverter is likely missing or not working (you can confirm this by turning the glasses upside-down—3d perspective will return). or, if you are using the 3d stereo sync cable, the 3d stereo sync setting in the advanced image settings menu needs to be needs to be toggled (inverted from its current setting).
image is breaking up: the horizontal back porch may be too small or too large. if you can lock to the signal by changing h-position but have a black left edge in the image, reduce the source’s horizontal back porch blanking. if the black edge is on the right, increase the source’s horizontal back porch blanking.
horizontal streaks in the image: you may need to adjust the clamp location option in the input levels menu (accessed via image settings menu) with 4- or 5-wire signals.
colors are “off”: if some grays in your grayscale appears tinted when viewed in 3d, your glasses may be slightly slow for the current signal setup. 1) if possible, adjust the projector’s dark interval control. 2) double-check timing adjustments to the source. 3) use faster glasses.