February 8, 2016 / Church Technology/
Projecting images onto non-traditional surfaces, rather than just projection screens, is not new. However, for small churches it’s still a relatively untouched technology. I recently did some projection mapping for a church youth event, and wanted to share how I did it without blowing the budget.
At Pulse, we used three projectors and mapped them onto three different surfaces:
- Left wall
- Centre screen (16:9)
- Right wall
These surfaces are all flat, and almost rectangular. On the side walls, the roof is angled towards a peak in the centre.
- Two short-throw domestic projectors (Optoma W316ST)
- One regular small venue projector
- Resolume Arena Media Server
- Matrox TripleHead2Go
- SDI converters
- Upright truss
- Ratchet straps
- MacBook Pro
This map shows the position of the two side projectors. These were mounted on upright truss, with a base-plate and ratchet straps.
This alignment may seem straightforward, and it almost is. That is, until you consider the angle of the lens and the position of the truss.
I used Optoma W316st projectors. These have a short-throw lens, with a ratio of about 0.5:1. It achieves such a short throw ratio with a fish-eye lens. The thing about a fish-eye is that it warps further towards the top of the image. When you mount these sideways like I did, the image on the right gets blown out. Long story short, it’s almost impossible to get it to fit cleanly on the wall.
Thankfully, I’d anticipated this and had a copy of Resolume Arena Media Server ready to go. It has built-in output warping.
As you can see in the above screenshots, the main canvas in Resolume has been split into three different ‘slices’. The canvas is 3x 720p images, with two in portrait mode. However, the output device gives me three 720p images in landscape mode. To match the dimensions of the side wall and compensate for projector over-shoots, the slices are rotated sideways and warped at the corners before being output.
This slicing and warping is the key ingredient. Being able to pull the corners in makes all the difference. The projectors are never going to line up perfectly with my irregular surfaces, and I can’t make all the content in the exact correct size. Hence, we transform it all on the fly with Resolume.
How bright was it?
With such a big surface and many lights to contend with, how did these little projectors fare?
Not badly, that’s for sure.
Yes, there were moments they were washed out. The colours weren’t always as vivid as I’d like. But overall, the effect worked.
These are DLP projectors. This means they can only do on colour at a time and have a colour wheel spinning around to output red, green and blue light. There’s a tiny amount of “rainbow effect” going on when you look closely, but at such a big scale it wasn’t very noticeable.
Also, the projectors were 3600-lumens each. My ballpark was 4000 lumens. I know if I sourced projectors of that brightness, it’d work out. While I didn’t quite manage to fit that ballpark into my pricing, I got very close and am happy with the results.
Here’s the thing… part of the intended ‘effect’ of the projection mapping was to throw up keywords and themes from the worship songs. These were almost always white, which is the strongest colour for a DLP projector. Even if the lights were going nuts, the animated typography was still visible and cut through.
James Eden created and compiled most of the content. This included:
- Lyrics overlays with alpha channel
- Pattern layers with alpha channel
- Gradient Overlays and Film Burns
- Background patterns / colours
We also created triple-wide announcement slides and bible verse slides for the message.
The full lyrics for worship songs were run out of ProPresenter 6, and output to a Blackmagic Design ATEM switcher where we keyed it over the centre screen’s output.
The disadvantage of doing it this way is that the centre screen gets delayed by a frame in the switcher. Ideally, we’d either run all screen through a switcher or we’d run lyrics directly into Resolume to be overlaid there.
How much did it cost?
- Short throw projectors – $1200 each
- Resolume (Full price) – $1200 (Thanksgiving special = 50% off)
- Matrox TripleHead2Go – $400
- SDI Converters – $1000
- ATEM TVS Video switcher – $1200
- MacBook Pro – $2000
Much of this I already had access to, so the projectors were the main expense.
Will you do it again?
I sure hope so!
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