RE: [Algorithms] FPS Questions

[Graham S. R. <gr...@se...>]

Steve Baker wrote,

> -----Original Message-----
> I suspect the limit would be the persistance of the phosphor rather than
> a limitation of the eye/brain.  All those neurons are firing
asynchronously
> so there will always be some that see the interruption to the light.

Its interesting that you mention persistence of the phosphor. We see an
artifact when using shutter glasses for stereoscopic viewing that may be due
to this effect. On a normal CRT screen, if you close one eye while wearing
shutter glasses, you see a shadow of the object, a second image that appears
to be the image for the opposite eye. When you are viewing the same scene on
a projection display system, the shadow is not there. Since the shadow goes
away with the projection system, I feel the shadow must not be leakage
through the closed shutter of the open eye. Our theory is that residual
light from the previous frame must be the cause.

> > [from my previous post - GSR ]
> > What happens in 5 years when we all have monitors running at 2000 pixels
> > horizontally? Large immersive displays such as CAVE's already run at 96
> > frames per second at that resolution... What happens when we are all
using
> > stereoscopic hardware all the time, so that each eye sees have the total
> > frame rate. 100fps becomes 50fps. We will then need 200fps to match
today's
> > 100fps..... Food for thought.
>
> No - that's not true.  We've run 3500x2200 pixel screens and 60Hz
> still looks just as good as it does on a 1000 pixel screen.

Steve, I don't disagree with you here. Sure, 60Hz looks just as good on both
screens. But think about stereoscopic mode (which is what I was talking
about). At 60hz total, each eye gets 30Hz. Well, that's not quite correct.
Each eye gets frames displayed at 60Hz, but rendered frames are delivered at
a rate of 30 fps per eye, with 30 frames of blackness in addition. The black
frames interlace with rendered frames causing opaque objects to seem
transparent. Even at 96 fps (the weird number used by the ImmersaDesk system
that we have used on contract to NASA Langley) opaque objects appear a bit
transparent in stereo mode. In the office, we try to run 120Hz on CRT's when
running in stereo mode. If you want 60Hz *per eye* in stereo mode, then I
believe you will need 120Hz total, unless you are using a display such as an
HMD that has separate screens for each eye.

I was at the IRIS Performer meeting at 1999 SIGGRAPH, and a demonstration
was given of the new Hayden planetarium projection display. This has
multiple SGI InfiniteReality2 graphics pipes driving seven projector
displays with more than 7 million total pixels (see link
http://www.trimension-inc.com/company/press_stories.html). As I recall, this
is running at only 30fps (it has a database of some 2 billion stars), and it
looks just fine. But objects are not moving that fast as the software
navigates through the stars. This is not a stereo display, though. The
actual display is probably running at 60Hz, and frames are duplicated as you
describe in your original post to get 30fps. I wonder if 60fps and stereo
mode would look good for this particular software and display system?

Graham Rhodes