The Cube

[BHawthorne]

Summary:

Working with 8x8x8 will give you also good results,

It really depends on the throw-ratio of your projectors and if you plan to put a full cockpit mock-up in it.

 

The Throw ratio determines your head/cockpit clearance - keep in mind that there is only one ideal view-point for a distortion-less view in a cubic projection.

 

To further elaborate, every projector has a spec that is called lens throw ratio. There are a segment of projectors called "short throw" lens projectors that are typically between 0.49:1 and 0.72:1 lens throw ratio. What most of us are using are 0.72:1 lens throw. These are the Optoma GT700/GT720/GT750/PRO450. They are all essentially the same projector with various different port setups. There are also 0.62:1 and 0.49:1 projectors but they tend to cost more per unit than the Optomas do. Depending upon the lens throw distance it dictates the cube size. What PeterP and Flim have shown is the 16:10 aspect ratio 0.72:1 lens throw build "ideal" cube size.

Edited March 17, 2013 by BHawthorne

[agrasyuk]

working on the drawing i read up on the optoma offering and it suddenly occurred to me that this projector is not offering any zoom and that 0.72:1 is constant. so thats why flim placed his inside the cube. hmm... that changes things...

[BHawthorne]

No need for variable zoom projector when you do the math before hand in CAD and use rigid fixed projector mounts in the proper location. Zoom lens projectors are for people who have to move the projector around often and need to accommodate different lens throw ratios. Lens shift and zoom lens options on projectors are just added cost.

[Flim]

I was just looking to see what new projectors were out and it looks like you can build a better cube now with this projector...

 

Benq mw820st Throw of about .5--- which you can project 96x60 image from 3-11" ft. Much better then the gt750e!

 

I did make a full 360 degree setup with top view at the first of the year... worked great with 2 670gt's.

[Dropship Pilot]

Flim,

have a look at he Acer U5313W - it has a throw ratio of 0.35:1! The price and the resolution is about the same as for the Benq. However with 0.35:1 you can probably place the side projectors just to the right and left of your pit on the ground. No need to have them "floating in the sky".

 

Cheers,

Stefan

Edited September 1, 2013 by Dropship Pilot

[HarSu]

Hi guys.

 

I'm not familiar of projectors but what you think of this product?

 

http://www.misco.co.uk/product/Q293350/NEC-U260W-2600-ANSI-Lumens-WXGA-DLP-Ultra-Short-Throw-Projector?selectedTabIndex=2&tabBarViewName=ProductTechnicalSpecifications&page=1tabs

 

I dont know is this good projector, but with this device you dont have shadows, right?

 

I found one place in Finland where it costs only 468€ each.

Pretty cheap, allmost free.

 

So what you think guys, should I buy five of those immediately or forget them?

 

HarSu.

[Dropship Pilot]

Sounds like a great deal! However, I sure am no expert on projectors.

So the only advice I can give is to make sure that it's really the same projector and not one of the same series but with a lower physical resolution or something like that. Sometimes the replacement lams are in that price region....

 

Cheers,

DSP

 

PS: I just saw that the contrast and brightness aren't too good with this one. Not sure if those values would work ok for a qube. What's the expert opinion?

Edited September 3, 2013 by Dropship Pilot

[BHawthorne]

Hi guys.

 

I'm not familiar of projectors but what you think of this product?

 

http://www.misco.co.uk/product/Q293350/NEC-U260W-2600-ANSI-Lumens-WXGA-DLP-Ultra-Short-Throw-Projector?selectedTabIndex=2&tabBarViewName=ProductTechnicalSpecifications&page=1tabs

 

I dont know is this good projector, but with this device you dont have shadows, right?

 

I found one place in Finland where it costs only 468€ each.

Pretty cheap, allmost free.

 

So what you think guys, should I buy five of those immediately or forget them?

 

HarSu.

 

Your projector location would most likely need to be on the floor right at the edge of the simpit for the left-front-right-back projectors. As a simpit is longer than it is wide you're going to have to account for that in projector location and dialing it in. Personally, I wouldn't mind having 5 of those projector personally to experiment with. 0.32:1 ultra short throws are only useful for flat screen surfaces. The distortion would be too great on a circular screen like mine. 0.32:1 is really short throw.

Edited September 4, 2013 by BHawthorne

[Suchacz]

I must say that those vids of cubic projection are really impresive!

 

But I think, that it would be even more immersive with 4:3 aspect ratio projectors. It should create bigger vertical view angle. Or am I wrong?

[BHawthorne]

But I think, that it would be even more immersive with 4:3 aspect ratio projectors.

 

Actually native resolution pixel height is the most important piece of information when it comes to something like this. Projectors can lock about any pixel width you want to feed them. I'd much rather do 1200x1200, or 1080x1080 than 800x800 or 720x720. You can lock 1:1 AR just fine on most modern projectors. That is why I'd get a 1920x1080 projector instead of a 1024x768 if budget wasn't a major issue. Projectors you need to think of them in a different mindset than LCD panels.

 

The second most important is the lens throw. You'll need to pick a lens throw that matches up well with what you want to do. In something like Flim's cube he's using 0.72:1. Might be more interesting to use 0.8:1 projectors and mount them behind the screen with a hole for the lens. Much less to obscure the ceiling projection that way. Lens throw and mounting location set the size of your cube. You can't just use random projectors in a cube design. You need to match the lens throw and mounting location to the size of the cube.

 

My idea for the cube would be to make a frame and stretch Rose Brand Tendo screen fabric to it. Would work great in a totally blacked out room where you wouldn't inadvertently have light bleeding in from the back.

Edited September 15, 2013 by BHawthorne

[X93355]

A friend of mine creates the high end custom first surface mirrors for cobra simulations.

 

http://www.bennettmirror.com/

http://www.cobrasimulation.com/

 

If anyone wants anything specific I'm sure they would be happy to look into it for you.

 

Craig

[BHawthorne]

It's best just to get the lens throw right on the projectors you get. Only panel that a mirror might be of use would be the ceiling, but you don't need anything special there, just a flat first surface mirror. Mirrors on a cube build would be in the way of the ceiling projection. Only reason to get mirrors on flat panel projection is if you don't understand lens throw.

[HarSu]

Hi.

 

Maybe stupid question but... Like Gadroc said in his post, http://forums.eagle.ru/showpost.php?p=1652870&postcount=211

 

"When using the CUBE project supported by DCS there is only one head position where everything looks perfect. That position is the direct center of the cube. In essence this means your normal sitting eye position should be directly in the center of the cube and at half the height of your walls."

 

So, does that mean that, if my Eye Position is in 114cm/3,74ft of the ground (measured by my youngest daughter...), that my cube must be at least 228cm/7,48ft of height and width?

 

Or should my eye position be center of projection area?

 

By the way. This projector http://www.misco.co.uk/product/Q2933...s&page=1tabs

It costs here in Finland only 294€ for now.

 

HarSu.

[geneb]

Not a stupid question at all.

 

Essentially, you want your head to be at the volumetric center of the cube. For example, if your cube was 2400mm x 2400mm x 2400mm, your head position should be 1200mm x 1200mm x 1200mm.

 

g.

[Flim]

The cube works... been tested with full 360+90 vertical projection on 1 gtx670/triplehead2go.

[Suchacz]

Hi Flim, can you make a video from pilot's point of view please?

[Flim]

I would, but I took it down a while back waiting for some better projectors and a finished pit frame. There are new optoma gt 760's out now that should be perfect for a smaller cube. I'm also about finished with the pit frame...

[agrasyuk]

Hi Flim, couple questions,

You said you sucsessfully projected the back view, I assume the proj for this view was ceiling mounted . did you find the position bothersome? It seems it will be positioned in a very awkward spot and almost always within normal field of view.

What was your projected picture height? Did you find pixel dencity of 800 lines completely satisfactory? Do you think there is a quality margin to use 720 or that will be just to low?

[BHawthorne]

800p is borderline, but when you have constant motion you tune it out. I'm really wanting to do a cube with BenQ W1080ST, but good luck getting the bank to get 5 of them. :)

 

On a separate note, you can find GT720 for around $400-450 now.

[agrasyuk]

yes, i'm watching GT720 and 750 auctions, can be had now for really nice price, even if you factor in a replacement bulb. while sufficient funding to get get 4 W1080STs is already secured with SO, i'm not yet sure that's the winner. as far as projection geometry and shadowing it looks like the mw820st fits so MUCH better , not to mention FPS, cost and rear view possibility without projector hanging right there in plain view.

 

BH, can you link to your setup? is the GT720X2 setup still operational? what is the eye/screen distance ?