[simpits-tech] Visual system questions (Gene) and an idea

[Gene Buckle]

On Tue, 31 Jan 2012, dabigboy at cox.net wrote:

> Hey Gene, in my research on visual systems, I came across a common issue 
> with curved/spherical screens and projectors. It has been noted that 
> even when you use software to warp and edge-blend the projectors for a 
> curved screen, areas further from the center of the screen go out of 
> focus. From the videos of your system, it doesn't appear this is an 
> issue, although I can't really tell for sure just from vids.....I would 
> guess that the relatively minor curve of your front-projection screen 
> keeps the focus issue to a minimum (another big advantage of your 
> system's use of a spherical mirror as opposed to projecting directly 
> onto a main screen), but I am curious: has this been an issue for you?
>
I haven't noticed any focus issues myself.  The curve of the screen that 
each projector covers is pretty shallow, so that helps.

> For folks projecting directly onto a curved screen, I have always 
> thought that it would be better to use some sort of lens on the 
> projector that would warp the image, as opposed to using software. I 
> even saw one sim builder mention this on the X-Plane.org forums, he had 
> a curved screen and mentioned just using a lens on the front of the 
> projector to warp things properly...I asked him about it but never got a 
> reply.
>
There may be a way to do this, but I don't know how.  Wayne might have an 
idea or two.

> It appears that the lens I seek is a simple fisheye/wide-angle lens, and 
> that planetariums actually use this concept for their projection 
> systems. It makes a lot more sense to use natural optics for the angle 
> correction, as opposed to taking away pixels from the image and trying 
> to shove it into shape with software. Plus you wouldn't need to spend 
> $500+ on warping software. :)
>
A lens that will properly distort the projector output will likely cost 
you a LOT more than $500.  It would have to be custom-ground, and would 
likely require more than one.

> Similarly, for people with cylindrical screens, a cylindrical mirror 
> could be used (I think?) whose angle is equal to the angle of the main 
> screen.
>
If they're using a fold mirror, then yes.  There's a guy out there that' 
built a Jet Ranger sim from a written off airframe and he uses a curved 
fold mirror against a curved display screen.  It's pretty slick.

> Brainstorming. Fun.......now I need to find my card reader so I can 
> upload pics of my Jeppesen/PFC yoke that I hackerized into my sim. :)

Neat!
g.

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