Re: Going big and stereo

New Message Reply Date view Thread view Subject view Author view

Angus Dorbie (dorbie++at++sgi.com)
Mon, 18 May 1998 11:52:33 -0700


Chris Jackson wrote:
>
> I'm developing an application that must be displayed at 1900x1200. I am
> currently implementing stereo graphics, and this output configuration is
> causing a dilemma...
>
> First off, quad-buffered stereo is out of the question because my
> hardware is restricted to "tiny" pixel depth at 1900x1200.
>
> So, I am resigned to using the top/bottom flavor.
>
> gfxinfo returns:
>
> Graphics board 0 is "KONAL" graphics.
> Managed (":0.0") 1280x1024
> Display has 2 channels
> 2 GEs (of 2), occmask = 0x03
> 4MB external BEF ram, 32bit path
> 1 RM8 board (of 1) 1/0/0/0
> Texture Memory: 16MB/-/-/-
> Small pixel depth
> 32K cmap
> Channel 0:
> Origin = (0,0)
> Video Output: 1280 pixels, 1024 lines, 72.00Hz (1280x1024_72.vfo)
>
> In general, I am wondering if stereo is even possible in this format, and
> what method would be most effective.
>
> Thank you for any help in advance.
>

You are going to have to reduce resolution, which top_bottom (SRT_RECT)
does by definition in Y. The high field rate in stereo vofs require lots
of bandwidth. Also display devices don't support the kinds of line
rates you need for these vofs. So start with your display and work back
from there.

It looks like you have a 1RM Reality (not Infinite Reality) so you don't
have a lot of framebuffer but you could config 2 * 1280x1024
framebuffer. You should explore getting 2 projectors and twinning them
feeding left and right eyes from different channels on the DG to the
projectors which will remove the per channel bandwidth limits and solve
any projector line rate problems.

Even if you had more RMs and an Infinite REality you cannot do 1900x1200
60Hz stereo, you don't have the RM->DG bandwidth or the DAC bandwidth on
any
channel. You couldn't even do 2*1900x1200 channels because of the DG->RM
bandwidth limit unless you squeezed video field rate to 50Hz.

You can get monitors which will handle moderately high resolution,
we saw one here which could sync to 1280x1024 120Hz (ie 60Hz stereo) but
this is better than a 120KHz line rate and that means a very expensive
monitor.

So, figure out the display you need, figure out whether you can afford
to
reduce your line count and whether you need a monitor or projected
display,
with multiple of single video feeds then you'll have a better idea of
what
kind of system capabilities you need.

Cheers,Angus

-- 
"Only the mediocre are always at their best." -- Jean Giraudoux 

For advanced 3D graphics Performer + OpenGL based examples and tutors: http://www.dorbie.com/ ======================================================================= List Archives, FAQ, FTP: http://www.sgi.com/Technology/Performer/ Submissions: info-performer++at++sgi.com Admin. requests: info-performer-request++at++sgi.com


New Message Reply Date view Thread view Subject view Author view

This archive was generated by hypermail 2.0b2 on Mon Aug 10 1998 - 17:57:24 PDT

This message has been cleansed for anti-spam protection. Replace '++at++' in any mail addresses with the '@' symbol.