Need a little help please

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Postby Kevin Sayre » Tue Oct 29, 2013 10:15 am

I have built a curved screen six feet tall and approximately eighteen feet wide for my flight simulator. I have purchased three optoma short throw projectors and will mount them to the ceiling. I have tested the set up and it appears that it is going to work. I have been tinkering with the software and can warp and blend but still having some difficulty getting things just right and need some clarification with the following. (1) One of the projectors-probably the forward view is going to have to hang closer to the ceiling than the other two...can this be corrected either by tilting the projector, keystone correction or with the software. (2) If some of the images spill off the screen do I make it smaller with the minus key or just use control points to drag the corners into the screen...what is the difference? (3) Do I warp and blend at the same time or warp the image, save it and then blend? (4) Finally should I physically move the projectors to get the red lines into place when overlapping the images? Any help is appreciated and I hope this makes sense.
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Postby BHawthorne » Tue Oct 29, 2013 11:06 am

The goal when setting up things as far as mounting points is to get as many pixels as possible into the screen height with a 15% overlap between the projectors. If there is more that is ok, but it affects how much detail is lost in the final resolution on the setup. Generally, what I like to do is take each individual projector and manually hold it while moving it around to find where the best mounting location is -- by seeing where I can get full coverage of 1/3rd of the screen + 15% for overlap. The mounting locations don't need to be perfect, because the utility allows you to calibrate as long as you have coverage.

I don't have any current examples of triple-projector configuration. Here is an example of dual-projector configuration though. This is what one of the projections looks like when accounting for a 90 degree arc of the screen. The red outline is the actual projection. The green outline is the 15% blend area. If you're doing 180 degree screen and three projectors, you'll have 60 degrees per projector requirement. The most important thing is to make sure as much of the projection vertical resolution is within the screen area as possible. In many cases you'll find a lot of overlap on the width. That's not an issue as long as you have at least 15% overlap.

Image
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Postby BHawthorne » Tue Oct 29, 2013 11:12 am

Not sure if you've seen this: http://nthusim.com/wiki/setting-edge-blending
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Postby BHawthorne » Tue Oct 29, 2013 11:19 am

"(1) One of the projectors-probably the forward view is going to have to hang closer to the ceiling than the other two...can this be corrected either by tilting the projector, keystone correction or with the software."

It's ok to adjust with keystoning a bit before adjusting in pre-warp. It makes sure as many pixels as possible are in the screen area. Every bit extra you can get into the projection height that isn't lost outside the screen is helpful. Keystone on projectors can help with that in many cases.

"(2) If some of the images spill off the screen do I make it smaller with the minus key or just use control points to drag the corners into the screen...what is the difference?"

The projection that spills off the screen is just lost pixels. No matter what you do you'll lose some resolution off screen or with the edge blend area. It's standard for correction of a flat projection onto a curved surface. Just make sure you have 100% coverage of the screen and at least 15% overlap for the edge blend. It's preferable to lose as few pixels as possible outside the screen, so be mindful of your mounting locations to account for the optimal location.

"(3) Do I warp and blend at the same time or warp the image, save it and then blend?"

I warp and blend at the same time. The picture above should give you a good idea of the 15% size for the blend. Just keep on fine tuning the blend until the red stripes are on top of each other in the edge blend area.

"(4) Finally should I physically move the projectors to get the red lines into place when overlapping the images? Any help is appreciated and I hope this makes sense."

No, the only moving that really needs to be done is initially making sure the screen has full coverage and that you have at least 15% overlap. No need to be perfect on this, just get it roughly into the ballpark. The pre-warp and edge blend will take care of the rest.

Be mindful that no two screens are the same exact configuration, so there is just as much an art as science to configuring. I'm in the process of writing up a new configuration manual. Any input you can give on what content you'd like to see would be useful. :)

-Brad
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Postby Kevin Sayre » Tue Oct 29, 2013 9:04 pm

Thanks for the help Brad should have the screen finished this week and projectors hung next week. Will post some pics when finished.
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Postby BHawthorne » Tue Oct 29, 2013 10:05 pm

Anytime, I have fun helping out with builds. Looking forward to seeing pics in the future. :)

-Brad
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