Projection screen - Curved vs Straight

[Sean]

Hi all.

I've not been very active for a while, but it's time to get this thing back off the ground. [sic]

Since getting the FDS shell, it became apparent that my existing projectors were not short enough for my setup (casting shadows), so I sold them and am looking to replace them soon. My Mk.1 curved screen was also just a temporary affair made with plastic tubing and bedsheets, so that's gone too. Also, the sim base wasn't deep enough to accommodate linked yokes (in the future), so that's bit the dust as well. So I have a clean slate and plan to build a new base (min. 200mm / 8" deep) and new screen.

Which leads me onto my point...

The planned visuals will be 3 projectors to give a minimum 180 degree external view. I had naturally assumed a curved screen was the only way to go, but before I start building proper, I'd like to consider the alternatives.

I've visited user Speedbird17 a couple of times. He also has the FDS shell and 180 degree visuals, but is using three flat projection screens angled towards each other. From memory, it was a setup that worked well, I don't remember any bad things about his visuals, but also remember him saying a future upgrade for him would be to a curved screen setup.

I also remember a past discussion here where a user is a member at a museum (in Scandinavia?) and they have two sims with 180 degree visuals, one flat, one curved, and there is no perceived difference between the two.

So I'm looking for comments on the issue. What are your thoughts, plans or experiences on this subject?

Sean

[Efe]

Hi Sean,
Good luck with your new build. I understand totally that you want to make sure you've thought the major things through before embarking on this long path. When you are saying curved, do you mean a straight panel place in a curve:



or a cylindrical curved screen:



Could you clarify just so we have an idea what you are considering, and we can better try to provide advice. Thanks!

[Sean]

Hi Efe

I was referring to a straight curve, your first option. But since you mention it, what advantages does the more complex curved screen give?

[Maurice]

I also remember a past discussion here where a user is a member at a museum (in Scandinavia?) and they have two sims with 180 degree visuals, one flat, one curved, and there is no perceived difference between the two.

Sean

I would strongly disagree here. Any curved surface (whether simple or compound curve) requires software to warp the image back into a rectangular projection. I can definitely state that the warping software degrades the image quality by an appreciable amount. I didn't think it would until I tried projecting with and without the warping software and I found the image looked much sharper without the warping.

But the biggest drawback of using flat screens and no warping software is that the alignment of the projectors is much more critical without the warping software since you cannot manipulate the image except by moving the projectors. And the image sizes must be identical which means very accurate projector placement. With the warping software, you can easily compensate for any misalignment or slightly different projection sizes.

So, bottom line, you have to choose what is most important to you...best image clarity or easiest projector installation. Knowing what I know now, I would try flat screens first and only switch to curved screens if I could not align the projectors properly.

That's my 2 cents and I'm sure there will be strong disagreements fronm others 

Maurice

[Sean]

I would try flat screens first and only switch to curved screens if I could not align the projectors properly.

That was my thinking, based more upon ease of construction rather than projector issues, but I can understand what you are saying.

I also didn't think that the warping software had that much of an effect. I had Sol7 running on my previous curved screen and wasn't aware of such a depreciation, but that said, it was a poor screen in terms of material and construction (basically a bed sheet hung in a rough curve from the ceiling).

Thanks for that.

Sean

[Maurice]

I also didn't think that the warping software had that much of an effect. I had Sol7 running on my previous curved screen and wasn't aware of such a depreciation, but that said, it was a poor screen in terms of material and construction (basically a bed sheet hung in a rough curve from the ceiling).

Don't get me wrong here...the difference is not huge but it was quite noticeable to me. You can easily see it for yourself if you just run FSX without warping and observe one small area of the screen where there is some fine details. Then run FSX with warping and look carefully at the same area.

When I did that, I noticed that some objects were definitely smaller overall with the warping than they were without the warping and consequently, they were not as sharp since they were somewhat compressed. This may  not bother you as much as it bothered me, so best if you do your own testing before taking my word for it 

Maurice

[FredK]

I believe the issue Maurice is referring to has to do with projector focus onto a curved surface. Warping software corrects for distortion but really does not correct for focal length.  Projector lenses are designed to focus uniformly onto a flat surface, thus there will be some areas of a crurved screen that are slightly out-of-focus.   You can see this effect when you play with the focus......some areas will be very sharp, other areas not quite so. Those areas will change based on where you choose to establish the sharpest focus.

I have a three projector system onto a curved screen using NthuSim and WideView. I find the immersive experience of the curved screen to far outweigh the drawbacks. I have my system setup with a bias for sharp focus near the screen centers.  It works well for me.  I really do not percieve any noticeable issues when flying.

[Efe]

I would think focusing on the middle (concave) area would be much more important than focusing on the edges and losing visual quality in the middle. Agree?

[Maurice]

What I said has nothing to do with focus. In fact, focus should be better in a curved screen since the distance from the screen corners to the lens would be the same as the distance from center of screen to the lens which is not the case with a flat screen.

As I said earlier, what I noticed was a size difference in objects due to the warping correction. The slightly smaller warped objects did not look as sharp as the same objects without warping. Not a huge difference but significant in my eyes at least.

I still have my curved screen but if I had to redo it, I would experiment with flat screens first.

Maurice

[Kennair]

All good points.  I notice a focus difference rather a clarity difference with projectors on a curved screen but I would be very interested to see the comparison on a flat surface.  I see many military sims often use 3 flat surfaces and Hans Krohn has a pretty impressive pit using flat screens (go to his Projection System) for reference.

As Maurice referred to, warping software enables easier manipulation of the image compensating for slight alignment errors in the projector locations, so why not use warping software on a flat screen?  While not needing the warp function you would still achieve its manipulation advantages and also its window border removal.

Just an idea.

Ken.

[Maurice]

so why not use warping software on a flat screen?  While not needing the warp function you would still achieve its manipulation advantages and also its window border removal.
Ken.

Very good lateral thinking here. This may well be the best way to deal with a flat screen.

Maurice

[Kennair]

Very good lateral thinking here. This may well be the best way to deal with a flat screen.

Maurice

Yeah adds to the cost of course but what doesn't in this hobby???    It would be so much simpler to configure however with no curvature issues to deal with.

Ken.

[sluyt050]

I believe the issue Maurice is referring to has to do with projector focus onto a curved surface. Warping software corrects for distortion but really does not correct for focal length.  Projector lenses are designed to focus uniformly onto a flat surface, thus there will be some areas of a crurved screen that are slightly out-of-focus.   You can see this effect when you play with the focus......some areas will be very sharp, other areas not quite so. Those areas will change based on where you choose to establish the sharpest focus.

I have a three projector system onto a curved screen using NthuSim and WideView. I find the immersive experience of the curved screen to far outweigh the drawbacks. I have my system setup with a bias for sharp focus near the screen centers.  It works well for me.  I really do not percieve any noticeable issues when flying.

Fred, good to read that you are very satisfied with your curved screen 737NG setup.

I would be very pleased if could provide me (and others) with the following info:
1. The effective image height you use (so after warp corrections),
2. The height of the lower image edge above the flight-deck,
3. The screen radius with the eye-point as a reference.

For your information, I am in the process of designing a 225 deg. curved screen for the 737NG, using 3 BenQ MW851UST projectors. The screen radius in my case is approx. 1.4m dictated by the available room size. With about 13% image overlap the result is an image height of 1,22m which is b.t.w. exactly the standard MDF plate size. I am doubtful, however, if this is sufficient.  The image will start at 529mm above the flight-deck (and approx. 649 mm above the floor in my calculation). Of course I realize that the required image height is directly proportional to the screen radius. So based on your experience, I can easily recalculate for my configuration.

I am inspired by the story of Ivar  Hestnes (http://www.nthusim.com/setup/ivar-hestnes-fsx-225-degree-visual). The warping software I plan to use is Immersive Display PRO from Fly-Elise-NG (http://fly.elise-ng.net/index.php).

[ivar hestnes]

Do you have my tutorial? It should help you on your way.

Just PM me your email, and I will shoot it over to you 

[sluyt050]

Do you have my tutorial? It should help you on your way.

Just PM me your email, and I will shoot it over to you 

Thanks Ivar,
Funny, I just sent you a personal mail since I was not sure you were actively following this post. Anyway, I have red your tutorial and have thoroughly studied it. Overall, it is quite clear to me how to make the setup. What is lacking, however, are details on the best image height and vertical position if the image in relation to the screen radius. With that information I know my minimum needed screen height and best placement of the projectors. So, experience from you and Fred (and others may be) in this matter is very welcome.

[XOrionFE]

Hello Edward,

Mine with the Mitsubishi Ew230u-st projectors is 12 ft diameter screen, 210 degree wraparound 3x70 degrees).  My screens are 4ft tall and sit 30" off the floor.   The projector lenses centers are aprox. 78" off the floor.

This gives a very nice view from inside the cockpit

Scott

[ivar hestnes]

Not sure if you have a shell to sit in...
But I would sit in the shell, and look out of the windows. Then have a friend to set "markers" outside of Max top and bottom you can see. That should give you an approximate of what height you want to stribe for.

Basically you either decide a total FOV, and get the height you get, or you decide a height, and the you get limited on how much FOV you can achieve. (overlap only affect horisontal FOV).

I am not sure where exactly the eyepoint is in FSX, but I assume it is slightly lower than middle of picture. This will make it harder to get the view all the way down. On my setup, I used middle of image as eyepoint, and I had to tilt the image slightly in .FLT parameters to be able to see the runway in front of me when on approach...

I follow all posts in this forum. This is a good community 

[sluyt050]

Hello Edward,

Mine with the Mitsubishi Ew230u-st projectors is 12 ft diameter screen, 210 degree wraparound 3x70 degrees).  My screens are 4ft tall and sit 30" off the floor.   The projector lenses centers are aprox. 78" off the floor.

This gives a very nice view from inside the cockpit

Scott

Thanks Scott,

Based on your data an image height of approx. 3 ft. (0.94m) would do in my configuration with a 9.3 ft (2.8m) screen diameter. Since I aim for a 225 deg. FOV my image height becomes 4 ft. which will be large enough for sure.

For the sake of completeness, your screens are 30" off the floor. I assume you do not mean your flight-deck, so what height is your flight-deck actually?

[Speedbird17]

so why not use warping software on a flat screen?  While not needing the warp function you would still achieve its manipulation advantages and also its window border removal.
Ken.

Very good lateral thinking here. This may well be the best way to deal with a flat screen.

Maurice

This is exactly my setup. Three flat screens and using Nthusim. I don't have to be too exact about Projector placement and flat screens are much more easy to install than curved screen - especially in my limited space.
Biggest issue is making the physical screen edge butting invisible.

Ralph

[sluyt050]

Not sure if you have a shell to sit in...
But I would sit in the shell, and look out of the windows. Then have a friend to set "markers" outside of Max top and bottom you can see. That should give you an approximate of what height you want to stribe for.

Basically you either decide a total FOV, and get the height you get, or you decide a height, and the you get limited on how much FOV you can achieve. (overlap only affect horisontal FOV).

I am not sure where exactly the eyepoint is in FSX, but I assume it is slightly lower than middle of picture. This will make it harder to get the view all the way down. On my setup, I used middle of image as eyepoint, and I had to tilt the image slightly in .FLT parameters to be able to see the runway in front of me when on approach...

I follow all posts in this forum. This is a good community 

Hi Ivar,

In fact I have no shell nor cockpit yet. It will be a generic one with 2 extra 27" monitors for 2D panels, but my screen configuration eventually must suite a 737. That's the reason I need experience input from builders like you.

The eyepoint location I got from http://www.markuspilot.com/.

[FredK]

Hi Edward -

Sorry for the delay in answering your question........

The following are the dimensions for my 737 sim......

Curved screen with 135 degree arc
Arc is 16 feet
Radial distance to pilot eyepoint is 82 inches (screen is offset to achieve a constant radial to the pilot's eyepoint)
Bottom of screen is 24 inches higher than the cockpit floor
Screen height is 48 inches (72 inches higher than the cockpit floor)
Distance to projector lens from screen is 48 inches (Mitsubishi projectors)

Using this setup I have an exact complete fill of the 16ft wide x 4ft high screen area after warping.  Note that this is achieved using a 4:3 projection aspect ratio to maximize height in my case.  Currently I am using Nthusim which only allows for butt edging for multiple computer projection.  I am planning to switch to Warpalizer for edge blending though. Based on my calculations I still will be able get complete screen fill using overlapping projection at a wide aspect ratio at the same projector distance to screen that I have now (which is as far from the screen as I can go given the space constraints that I have).

My cockpit dimensions (glareshield height and window dimensions etc.) are accurate to the real thing.

Fred

[sluyt050]

Hi Edward -

Sorry for the delay in answering your question........

The following are the dimensions for my 737 sim......

Curved screen with 135 degree arc
Arc is 16 feet
Radial distance to pilot eyepoint is 82 inches (screen is offset to achieve a constant radial to the pilot's eyepoint)
Bottom of screen is 24 inches higher than the cockpit floor
Screen height is 48 inches (72 inches higher than the cockpit floor)
Distance to projector lens from screen is 48 inches (Mitsubishi projectors)

Using this setup I have an exact complete fill of the 16ft wide x 4ft high screen area after warping.  Note that this is achieved using a 4:3 projection aspect ratio to maximize height in my case.  Currently I am using Nthusim which only allows for butt edging for multiple computer projection.  I am planning to switch to Warpalizer for edge blending though. Based on my calculations I still will be able get complete screen fill using overlapping projection at a wide aspect ratio at the same projector distance to screen that I have now (which is as far from the screen as I can go given the space constraints that I have).

My cockpit dimensions (glareshield height and window dimensions etc.) are accurate to the real thing.

Fred

Hi Fred,

Many thanks for the data and the pictures of your cockpit. Looks very good.
I can now finish my paperwork. Still not very easy since I have less space than you and I have to deal with a pitched roof! But I think it will just fit. Looking at your pictures I wonder that you have so much coverage of your side windows considering the 135 deg FOV. Unless  your eye-point is ahead of your screen center.....I cannot explain it otherwise. Anyway, you managed it.

Success with your re-warping!

Edward