Re: Large FOV

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Angus Dorbie (dorbie++at++sgi.com)
Mon, 14 Jun 1999 16:11:38 -0700

Devrim Erdem wrote:
>
> > Which distortion are you thinking of? Error as viewer moves away from
> > the design eyepoint? Different packing of world-space information into
> > displayed pixels as you move from the center of projection toward the
> > edges? Errors of fog or lighting based on the common "Z-depth" rather
> > than correct "radial range" as a function of FOV? Loss of Z-buffer
> > resolution as a function of angle or distance from the center of a wide
> > FOV display? Light fall-off from a flat screen based on angle of view?
>
> I can not think of the distortions you mentioned since this is my first VR app
> using large FOV. A frog in a well says "The sky is as big as the mouth of my well".
>
> AFAIK, I shall expect a distortion when horizontal FOV exceed sth like 60. I was told
> in a Vega training that this is because of the difference between a rectangle and
> pie slice. The solution was to use 2 channels instead of one. Now I wonder if the
> can be guessed correctly to prevent motion sickness or other problems.
>
> Secondly, which one of the distortions you mentioned is most likely to appear ?

The one you are most likely to encounter is simple geometric inaccuracy.
It's listed above as "different packing" but is really a manifestation
of your display geometry not matching your 'virtual' projection
geometry. A good display solution for a cylindrical screen would include
some form of distortion correction capability or appropriate physical
alignment which will allow you to approximate the display geometry using
a series of flat faces then correct in the projectors using a test slide
and manual adjustment.

You are not providing enough data about your display and application to
allow us to provide a solution.

Cheers,Angus.

-- 
"Microsoft's system was like a forest that hadn't had a controlled
 burn in decades, just waiting for one person with a match to turn
 it into a disaster. Melissa was Microsoft's fault. They left their
 system wide open to this sort of abuse, they knew it could happen
 and did nothing." -- Bruce Perens


For advanced 3D graphics Performer + OpenGL based examples and tutors:
http://www.dorbie.com/

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