Screen Warping and Alignment

[RayS]

I wrote this up over the weekend. I hope it can help someone else with the black art of screen warping.

Aligning a screen:

I have a 3-projector setup, resulting in a 204.5-degree wraparound screen with a 6-foot radius (12-feet in diameter)

I use FLyElise Immersive display Pro. A few months ago I tried using their Immersive Calibration Pro software using 3 cameras exactly as outlined in the instructions. This methodology was an exercise in futility. The software is buggy at best and would crash repeatedly across multiple computers (of course without saving your work). If you DO happen to use this method, be warned that you CANNOT go back later and nudge a few pixels around to make it better. No- You have to set all your cameras back up *exactly* the way you had them before and start all over.

Tools Required:
1. Bosch GLL40-20G Green-Beam Self-Leveling Cross-Line Laser (Or equivalent)
2. Sturdy tripod
3. Beer and Or any adult beverage (Be aware that alignment quality will diminish with time and consumption...)
4. A willing participant (Helps to speed things up. Be aware though that supplies indicated in #3 will diminish at a faster pace.)

My Setup:
Projector overlap is roughly 18 inches between 1 & 2, and 2 & 3. (Your  overlap may vary)
Projectors sit roughly 18 inches above the top of the screen, and roughly in the center of the circle created by the screen dimensions
Screen is circular, with a 204 degrees circumference and a 6-foot radius.

SUPER-IMPORTANT:
Be certain the hot air exhaust from one projector isn't blowing into another projector air intake. Use baffles to block/redirect the hot air away from the other projectors.

PRO TIP:
Make sure your screen is level. Not to the dwelling or enclosure but to gravity, since you'll be using an alignment laser that uses gravity for it's own alignment.

1. Settle in. It's going to be a long weekend.
2. I prefer a green laser. Much easier to see than a red one, but the green can be a bit too strong in some cases, depending on your screen color.
3. Divide the screen into row/columns evenly. Like... super-evenly.
4. If a row or column measurement calls for 5.65 inches, get as close to that as possible. Accuracy is key.
5. Always work from left to right, or right to left. I've found that reversing or randomizing the workflow is asking for trouble and frustration.

Video Card:
I have my video card and 3 projectors configured as 1 "Logical" display. It seems the alignment software likes this much better. (Although you will still need to set the projector profile to "3x1" in the warping software)

PRO TIP:
SAVE YOUR WORK. And...
The more control points you have to work with, the more accurate your results. (But this does increase time required) I use 11 points across, 10 points down for each projector

Starting:
Once you have the screen evenly divided and marked, I've found it much easier to then add some fluorescent string to demarcate the vertical divisions. It's a tedious task but you'll thank yourself for this later.

Using your laser, begin adding the string to each vertical division, getting it as close to the screen material as possible, otherwise you'll be dealing with parallax issues which affects the alignment accuracy as the hours and beers go by.

After this exercise you'll have even vertical indicators which makes alignment much faster, relatively speaking.

The next step is several fun-filled hours of nudging pixels until the entire screen is full aligned. To do this properly, I highly suggest you perform TWO full-screen alignments. THe first pass will be what I consider a coarse alignment. Just get everything in the ball park.

PRO TIP:
SAVE YOUR WORK. And...
Using your keyboard, adjust each point Left/Right FIRST, then up & down. Depending on several factors like screen curve and beam angle, moving a control point left & right will ALSO move the point up and down a bit. This is more noticeable at the edges.

(Using a mouse to do this will cause temporary insanity... Use a keyboard. You're welcome. :-) )


Beginning at the screen top left (Or top right) along the first top row: Move the laser across the entire span of your display, align the entire row across all projectors, then move on to the next row down.

PRO TIP:
SAVE YOUR WORK. And...
Don't bump the tripod holding the laser! Otherwise you may have to start the row all over again.

Save your work after each row. Lather, Rinse, Repeat.

After you've completed aligning the entire screen, take a nice break.

When you're ready, do another full alignment but this time you should only have to eyeball the vertical and horizontal lines to see how straight they are. Chances are you should only have to nudge a few, near the edges and corners. Remember to ALWAYS work from one side to another. Resist jumping around. Trust me on this. :-)

PRO TIP:
SAVE YOUR WORK. And...
The diamond-shaped control points DO NOT.... I repeat DO NOT map to displayed columns! (Although they do map correctly to rows... go figure)  This is not an issue if you aren't going to edge-blend, or if you are only aligning 1 projector. If you ARE going to edge blend, a successful edge-blending is accomplished by ensuring that the image you've selected during this process blends properly with the adjacent projector. If you started from Left to Right, this only applies to the left-edge of projector #2 and #3. Make sure the right edges of  all your projectors adhere to your division lines. It's only the left sides of #2 and #3 where the black art of blending begins. (Reverse all these left/right references if you started from the other side :-) )


Conclusion:
I've done numerous screen alignments since 2014 and with every alignment I learn something new. Please feel free to add your own findings/advice!

[FredK]

Ray gets a gold star for documenting all that!  I can't dispute anything there.

There is one consideration to add though (that I think is important) that relates to maximizing on-screen pixel density.....

First, attempt to mount your projectors so there is minimal "native" keystone. This gets back to carefully planning the layout of your physical cockpit and assessing the optimal physical space to avoid projecting at crazy angles. For example, my Optoma HD Darbee projectors are set about 8-9 inches above the top of the screen as measured to the center of the lens. The important thing is that this provides an absolute vertical edge for each projection in my case. This is close to the spec for those projectors, however the height of each one is actually a bit different (as much as plus/minus 2 inches or so). So check each independently.

Second, there is the question of overlap vs. butted projection.  The advantage of overlap is the absence of any perceived projected edges.  The advantage of butted is maximized on screen pixel density. The latter is very significant....I leave you to do the math on that.

I have been using projectors for over ten years now.  I started with overlap but went back and forth between that and butted.  For the past 4 years I have been locked on to the butted method. 

By maximizing pixel density you can achieve better clarity, minimize washout, and eliminate perceived pixilation. Granted there is a fine edge line that is visible, but in the case of overlap there is also that wide band overlap area that never really comes out perfect (at least in my case).  The butted method is also easier to maintain since any minor misalignment will be less noticeable (as opposed to creating a blurriness in the overlap region). The butted method will also work better for night flying...blinders can be installed to completely eliminate any overlapping region.

I only offer this as a suggestion of course.  When it comes to visuals what is important to one may not be to another. It is highly personalized as we well know. For me, once I am engaged in flying I do not even notice the edges at all. The crisper clarity I get is a much more important factor to me.

Fred K

[KyleH]

Let's leave the projectors vs. TV/monitors comments to those specific threads, so we can keep helpful threads like this on topic for those who wish to pursue this route.