My plannend setup for racing

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Postby Ben » Wed Nov 06, 2013 8:48 pm

Hello,
i planed a 3 projector setup, mounted over my "chair similar to a monocoque"

Bevor i spend a lot of money i would be very glad if you check my setup/ give my some expert advices! :D

screenangle: 180°
screen diameter: 4m (13.1 feet)
projector type: Optoma W305ST:

-resulotion: 800x1280
-throw ratio: 0.52:1
-( http://www.optoma.de/projectordetails.a ... &PC=W305ST )

i made a sketch with 15% overlapping and placed the projector pictures in the edges of my 66° screen angle
with the throw ratio 0.52.

is my design correct?

after working with nthusim, is the screen 800x3840 or 800x3456 ?
so regarding 4m diameter i get a total screensize 4/2*pi= 6,3m by 1,30m high.
or is it because the overlapping 6,3m by 1,45m ?

With witch tolerace (in projector mounting) can nthusim work with?

Is there a projector type more suitable for my needs?

thanks a lot!
Ben


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drawing projector places
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total view
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Postby BHawthorne » Thu Nov 07, 2013 1:01 am

Looks good from what I see. I'll go over the details later today on the projector calculator pro specifications on the projector to make sure the numbers are accurate. 13.1 feet diameter is a lot like my first few screens I did back in 2009-2011, so I'm really familiar with that size. :)

http://www.nthusim.com/setup/amd-tech-day

The setup above is a 13 foot radius screen. I believe it was a 150 degree and not full 180 degree arc though. It was done in 2010 before we had edge blending mode in. In that particular setup we edge butted the projections. You can tell in the pictures where we did the projector edge butting. If I recall we had a lot of excess projection width because of that. Also, because we were supposed to promote F1 2011 for Codemasters at that event and ended up using iRacing at the last minute the FOV in iRacing isn't set right. The in-car visuals looks too big. Minor nitpicks on the setup as I look back at it. All that can be fine tuned to proper FOV and configuration though.
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Postby Ben » Mon Nov 11, 2013 7:51 pm

Hello,
thank you for feedback!

Your setup looks very nice. :D

I tried the projector calculator pro, but yet there is one question:

The "throw distance" changes from the edge to the middle of one projector screenn, compared to a flat screen.
Witch throw distace i have to use for my calculations, or is it a tolerance Nthusim can handle with?
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Postby BHawthorne » Tue Nov 12, 2013 1:03 am

The distance that matters is an imaginary line that spans between the two edges of where the projection hits. It's a line that is floating in front of the screen arc. It's also the location of because how projection geometry works of the shortest projection height. The center of the projection will have more projection height because that is falling on the screen further back than the edges. You always have to think of measurements in the context of the shortest projection height areas of the projection to ensure you get full coverage.

The main priority it to just ensure you have full projection coverage of a screen area with as few pixels falling outside the screen height as possible. You'll always lose projection width because there is more there to use than is needed. Triple 16:9 and 16:10 projection can do around 225 degrees, but games only really handle camera FOV settings up to 180. After 120 it starts to have fisheye distortion, so you have to compromise a bit and fine tune it to what looks best to you. There are exceptions to that in FSX and DCS World, but that isn't the norm.
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Postby Ben » Wed Nov 13, 2013 9:15 pm

Ah ok.
My sketch with FOV 180 degree is not a dogma, my aim ist to make it as realistic as possible.

I also thought about 120 Degree with two 1080p projectors.
Because I never seen a installation like this I cant imagine what looks better.

So would you rather recommend that to me?
How important is the resulotion of the projector?
(800x1280 vs 1080x1920, is there a noticeable difference (13feet room width?))

If I choose 120 degree FOV, how important is it that the drivers head is in the center of the screen curve

I play rFactor 1/2
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Postby BHawthorne » Thu Nov 14, 2013 1:16 am

A primary consideration between 120 degrees and 180 degrees is peripheral view. You can pan your head left and right with 180 degrees and have a sense of peripheral view, while 120 degrees is just forward facing view.

1080p will always be sharper than 800p. I use 800p projectors as a compromise based on price. It's not my ideal. I would rather use 1920x1080 or 1600x1200 native projectors. At issue is I can get two 800p short-throw projectors for the price of one 1080p short throw projector and 1600x1200 projectors aren't even in the consumer price range. If you can afford it, always go 1080p.

The edge blend being at the center of the field of view with dual-projector is a minor annoyance. You need to be very exact with your edge blending or you'll notice it. that being said I do dual-projector 180 degree on my screen. If you go dual-projector and Nvidia video cards you'll need to use a Zotac DisplayPort to Dual HDMI active adapter to achieve the span. With AMD video cards you'll be able to do it via Eyefinity 2x1.
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Postby Ben » Thu Nov 14, 2013 2:23 am

OK. i have to think about 120 degrees and 180 degrees a while.

I made a second sketch with 120 degrees, 2 projectors BenQ W1080ST
(because you recommend that and because its not easy to find 1080p short throw projectors)

The problem now is that there are no space for two projectorsm if i calculate the
"imaginary line that spans between the two edges of where the projection hits" and the throw ratio (=0.7)

Can I use a vertical offset between both projectors?
In my mind it seems logic that my head have to be in the center of the arc/ the curved screen. But I saw pictures where its not.
How it is?

Grafics card: i choosed AMD, HD 7870 (up to eyefintiy 6 Monitors)



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Postby BHawthorne » Thu Nov 14, 2013 7:10 am

By the looks of your diagram you're taking projection width into account but not projection height. I keep pulling back the mounting location till I have the projection height I want. No matter what you do, you're going to lose pixel resolution in the width, simply because of how the aspect ratio works on the projections in a span is wider than needed. The important measurement is to ensure you get everything within the height with some excess projection width spilling outside of what is needed. I guess the easiest way to explain 180 degree Eyefinity 2x1 is to show pics of the configuration. Note the second pic below for example to this.

Here is a panoramic view of the screen I just quickly snapped with my iphone. Make note that the projectors are mounted so the projections cross each other, not mounted at the center. They're a bit off of the center line of the screen arc and pulled back to where I can get full coverage on around 105%. Geometrically speaking, we're working with 16:10 aspect ratio 0.72:1 lens throw projectors, 60" screen height and a screen radius of 60" (5 foot). My mounting location force me to mount the projectors roughly 32" beyond the 180 degree screen edge at about 32" from each wall (rough figures).

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Here is a pic I'm taking from another thread where I was showing what the projection looks like uncorrected in alignment to 1/2 of the screen. The red outline shows the outer limits of the projection. The green rectangle shows the center blend 15% area.

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A random pic of the screen after it's finished calibration and in use.

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Some of the concepts that you can take into account when designing the screen.
  • Mounts do not have to be exactly on the center line. They can be slightly offset as long as you have screen coverage and focus range.
  • Projection beams can cross each other without effecting the projection.
  • You can mount beyond the center point of the design depending upon how your lens throw dictates mounting points.
  • Think in terms of projection height. It is the most important criteria in the design.
  • You will always lose pixels outside the screen and calibration area. It's the nature of geometrically correcting a flat projection onto a cylindrical screen surface. The trick is to minimize the pixel loss on the height of the projection.
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Postby Ben » Fri Nov 15, 2013 6:41 pm

Ok thanks a lot!

I will think about 120 degrees with 2 projectors and 180 degrees with 2 or 3 projectors.

One question is remaining:
The position of the gamer: should the persons eyes in the center of the screen arc (sounds logic, in my opinion), or somewhere between center and screen (as I saw on pictures). Can I calculate this or is it trail and error?
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Postby BHawthorne » Sat Nov 16, 2013 1:40 am

Ben wrote:Ok thanks a lot!

I will think about 120 degrees with 2 projectors and 180 degrees with 2 or 3 projectors.

One question is remaining:
The position of the gamer: should the persons eyes in the center of the screen arc (sounds logic, in my opinion), or somewhere between center and screen (as I saw on pictures). Can I calculate this or is it trail and error?


It's dependent upon the content you're viewing. With simulation I like to be at the center point, with movie content I like to be 8-10 foot back from the screen. I use my screen for general use, so it's not tasked for anything specific. My gaming chair moves around depending upon what I'm doing with the screen. It's mostly trial and error. Most of this is truly trial and error. My suggestion would be to test the location and shift things to where they work best. I do understand the want to get the math right before the build. It helps you minimize the unknowns, but you'll find that you'll have minor tweaks to things to dial things in better once you begin. It's just as much art as science because no two screens are alike. My suggestion is to go into things working out the math, but realize it just gives you a starting point. You'll find that you'll be moving things around slightly once you get everything installed to get things where you feel they should be best.
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