Techniques for aligning projector pattern?

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Postby Shack » Fri Jun 12, 2015 10:15 am

Wondering if anyone has any techniques for aligning the projector pattern (at the bottom corners as you can see here) in order to facilitate edge blending the different projections? BenQ W1080ST projectors.

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Postby BHawthorne » Fri Jun 12, 2015 10:34 am

Typically, what I do is set the no-signal background color for the projector to something other than black. I typically use blue. I measure off 1/3rd of the screen. My goal is to have 100% of one third of the screen be filled up by each projector with a bit of overlap between for edge blending.

This can be done without even having a computer connected to the projectors by using the no-signal blue screen. Some of the pixels will be falling outside the usable area. That is normal. The idea is to minimize the pixels falling outside the screen, but still achieve 100% coverage. You'll find that with a curved surface that there will be a bow in the projection. That is normal. Some of that bow will fall outside the screen. That is also normal. Keep on moving around the location of the projector till you are happy with the coverage of the screen then affix the projector in that location. Do that with all three projectors.

What Nthusim does is takes the area that has projection coverage and calibrates it to the screen using a grid of column and row control points. Account for 15% overlap on the edges so you have enough for the edge blend. It's also ok to have more than 15% overlap. Some screens will have more overlap than others. It's all ok as long as you make sure you have at least 15% overlap.

It's a lot to figure out at once. If you have any questions I'm here to help walk you through any issues though.
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Postby Shack » Sat Jun 13, 2015 5:58 am

Makes perfect sense Brad. I appreciate your commentary. My projectors are way too close. I'll readjust and report back.

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Postby The_Nephilim » Sun Jun 14, 2015 2:57 am

do't forget to have Eyefinity or NVidia Surround enabled too ;)
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Postby Shack » Mon Jun 15, 2015 6:11 am

Ok, Ive readjusted my Projector distances to get the best possible coverage, (given my room size). I exceeded the screen area in some places. Im still experimenting with keystone to see if I can pull it back to a more manageable solution.

Ive created some vertical and horizontal control points, but I don't see how I can match up the red "barber pole" pattern as it stands now. Any input here please?

thank you,

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Coverage test pattern only:

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Postby BHawthorne » Mon Jun 15, 2015 9:18 am

Don't use keystone because that isn't actually optically putting more physical pixels in the screen area. Keystone is done digitally, not optically. It's best to have your keystone set to "0" and work from there. If you could, set all the projectors to "0" keystone. You might have to re-work the mounting locations if the keystone was greatly effecting the projection.
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Postby BHawthorne » Mon Jun 15, 2015 9:38 am

Here is a marked up picture. The green represents the three projection areas. Notice how much is falling outside the screen. This is normal for full coverage. The red represents the 15% overlap area that will be the outer edges of the calibrated edge blend. Notice that the edge blend area is smaller than the overlap. That is all ok. It's normal.

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I'm making an assumption that you've applied a lot of keystone to your setup in the photos so I've not gone with the same projection area size that you have in the photo. The overlap areas can be wider than I show in my markup but generally it would look similar to how I have it marked.
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Postby BHawthorne » Mon Jun 15, 2015 9:56 am

Here are a few pictures using my screen that I just shot.

The screen with the projector test grid shown simular to how you are using it.
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The Nthusim calibration screen with the 15% edge-blend and grid columns/rows added to align the projection using the F1-F4 keys.
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Nthusim Plus 4.0.226 using WDDM (desktop) mode after calibration.
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A bit of random gameplay. Playing Star Trek Online.
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Postby Shack » Mon Jun 15, 2015 12:42 pm

Thanks for the graphical examples. Those are very helpful.

It appears as if the only way I can get that coverage is to move my projectors even further back away from the screen ( right up against my wall ). They're at 94 inches right now. ( BenQ W1080ST )
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Postby BHawthorne » Mon Jun 15, 2015 1:41 pm

That or maybe not use the full height of the screen. I have a Benq W1070 in one room. It has a variable zoom lens. Does the W1080ST have the same zoom lens setup? If so, you might be able to dial it in a bit more with the variable zoom. My triple projector setup is Optoma GT1080. Both the Benq W1080ST and the Optoma GT1080 are my current projector picks for multi-projector. I have no first hand experience with the W1080ST, only with the W1070. A lot of Nthusim users have used the W1080ST to great success though.
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