3.5.5 Atmospheric Effects3.6 Display Subsystem
Also new with SkyWriter is the ability to perform fog and haze computations on a per-pixel
basis. This provides atmospheric effects that can be localized with an appropriate drop-off with
distance from the viewer. These effects also ease the simulation of clouds, scud, and other
environmental conditions. The fog color is user selectable and is blended with the colors of the
objects it affects.
SkyWriter has an innovative and flexible display subsystem capable of scanning the digital
frame buffer out to video at varying resolutions and pixel timings. High speed digital-to-analog
converters (DACS) combined with custom circuitry enable software programmability of video
output formats without requiring any hardware or PROM changes. Much of this display
technology has been leveraged from the PowerVision graphics architecture, the VGX,
providing a high level of compatibility between SkyWriter and lower cost systems for
instructor stations, database development, and ancillary displays.
3.6.1 Programmable Video Formats
The standard SkyWriter system is delivered with a display subsystem capable of generating a
wide range of video output formats. Incorporating an advanced Video Output Formatter
(VOF); SkyWriter is capable of driving any display from 1x1 pixels at 1 Hz to. 1280x1024 at
60Hz non-interlaced. Using some special microcode, SkyWriter can even drive HDTV
displays adhering to the NKK standard (1920x1024 - the actual standard has 1035 vertical
lines, but SkyWriter can drive it with 11 blank lines).
Included with each system are the VOFs to support the following resolutions:
o High Resolution 1280xl024@60HzNon-Interlaced
o High Resolution 1280x1024@30Hz Interlaced
o HDTV 1920x1024@ 30Hz Interlaced
o RS-3431280x960@30Hz Interlaced
o Stereoscopic 1280x492@ 120Hz Interlaced
o Stereoscopic 1280x5l2@ 120Hz Interlaced
o PAL780x575@25Hz Interlaced
o NTSC645x485@30Hz Interlaced
While all of these resolutions are included as standard VOFS, others may be added at any time.
For custom VOFS, Silicon Graphics will perform the necessary microcode development for
non-recurring engineering costs that are quoted on a case-by-case basis.
3.7 Video Options
In addition to the standard display options available from the SkyWriter display subsystem,
there are a variety of video option boards available for a variety of functions, including video
image capture and recording. The following list represents all of the currently available
options and describes their operation.