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# Camera rig for video projection on 4 walls of a room

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 Camera rig for video projection on 4 walls of a room on Nov 8, 2012 at 12:42:17 pm

I'll just dive into the situation. I've been asked to develop a video that will be projected on the four walls of a ballroom. It's not the ring shaped 360° projection since it's just a regular right-angled room. Each wall uses Watchout and 4 projectors leading to a total of 16 projectors in the room. Each wall gets its own video stream but the videos are synced to play simultaneously giving the impression of a 360° experience

My intended video uses 2.5D and some 3D and will be executed entirely within After Effects. The screen size I'm using for each video wall is 1920x480 square pixels. The master comp is 7680x480.

My problem arises with getting the camera rig set up. I've got 4 cameras rotated in increments of 90° to simulate the views for the 4 walls but I've been tripping up on getting the edges of the four viewports to line up in my master composition. Is there some way or method to achieve or calculate the camera placements so that the edges line up for the 360° view? Furthermore, if there is a mathematical solution to this then can it be extrapolated to factor in the use of different focal lengths within After Effects? At this point however I'd just be thrilled if someone could shed some light on how to achieve this using the standard 50mm AE lens.

Many thanks in advance for your attention. I hope there's enough information in this post. If I've left something out please let me know.

 Re: Camera rig for video projection on 4 walls of a roomon Nov 8, 2012 at 3:10:54 pm

Haven't done it myself, but perhaps you need to this tutorial -
http://library.creativecow.net/articles/larsen_carl/cube_world1.php

At end, you would render out 4 files each with the camera shifted 90 degrees on the x-axis.
Time permitting, you may also want to render out one more file at a substantially reduced resolution of the Master Comp for the Watchout programmer to use as a representation of the whole in his Watchout Production PC. Not an absolute necessity, but it allows the programmer to see the show in one flat window pane.

 Re: Camera rig for video projection on 4 walls of a roomon Nov 9, 2012 at 5:40:43 am

Thanks for that link Thomas. It certainly helps. Your suggestion to provide the operator with a flat render is very well noted and I'll certainly be doing that. Really appreciate your input.

All hail the cow!

 Re: Camera rig for video projection on 4 walls of a roomon Nov 8, 2012 at 4:37:37 pm

If you want the edges of the cameras fields of view to line up then you shouldn't assume that the standard ("50mm") focal length is the correct one to use.

Depending on the lengths of the walls you'll actually need to use different zoom (focal length) values. If all the walls are the same length (square room) then you'll enter half the compositions width in the zoom value of each camera. This will give each camera a 90 degree horizontal field of view. 90 degrees x 4 cameras = 360 degrees.

Darby Edelen

 Re: Camera rig for video projection on 4 walls of a roomon Nov 9, 2012 at 5:50:11 am

Stellar advice Darby. It worked like a charm. Should any other novice, in the future, require a quick start to a project like this I've uploaded my basic rig that uses expressions to set the focal length of each camera to half the width of the comp. Additionally, the Master Cam Null Controller impacts the rotation and position properties of all the cams in the 4 viewports. Hope this helps others. You've been a tremendous help.

All hail the cow!

 Re: Camera rig for video projection on 4 walls of a roomon Nov 9, 2012 at 3:40:11 pm

I'll add the same warning that I did in my initial post here: 90° horizontal field of view is only for a square room :)

If the room is rectangular then you may need, for example, two cameras with 120° horizontal field of view to look at the long walls and two with 60° horizontal field of view to look at the short walls. I picked those numbers randomly, but based on the sizes of the walls (and therefore compositions) you can figure them out with some simple Trig.

Darby Edelen

 Re: Camera rig for video projection on 4 walls of a roomon Nov 12, 2012 at 5:29:50 am

I guess it's a good thing that my room is a square this time around. You see, I was always back of the class at Math, so what you call 'simple trigonometry' was more like 'trigono-mommy!' for me :D

If you'd like to help out this hapless soul a wee more, and when you have a little time, could you help me get my head around the trig involved. I'm pretty sure (with my kind of luck) I'm going to need it sooner or later. Cheers.

All hail the cow!

 Re: Camera rig for video projection on 4 walls of a roomon Nov 13, 2012 at 7:44:18 pm

[Kunal Puri] "If you'd like to help out this hapless soul a wee more, and when you have a little time, could you help me get my head around the trig involved. I'm pretty sure (with my kind of luck) I'm going to need it sooner or later. Cheers"

Well, it takes some simple trig as well as an understanding of what the 'Zoom' property on the camera represents :) So here's an image to help explain.

Note that once you follow the simple(r) process at the top of the image, you could just scrub the 'zoom' values of your cameras to get quite close to the correct field of view. The rest of the image goes into the trig which could be used to create an expression on a camera's zoom property.

Darby Edelen

 Re: Camera rig for video projection on 4 walls of a roomon Nov 14, 2012 at 10:29:24 am

Darby...what can I say. You just assumed legendary status for that last post. It's worth framing, which is precisely what I'm going to do for the other lads and lasses at work. As elementary as it may seem to you, this stuff doesn't come easy to a bunch of us so take a bow and imagine a standing ovation. That schematic should be in a book.

All hail the cow!