First time building facade mapping advice

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First time building facade mapping advice

Postby pablitof » Fri Jan 16, 2015 11:21 pm

Hi everybody,
I was hired to make a projection mapping on a not very complex building facade. Since I also have to produce the content in After Effects (and create masks for windows, doors, and decorations) I have a doubt on how to proceed for this specific situation.
In the past I always projected on quite small objects and usually had the projector aligned to the viewer's point of view and took the reference picture from there.
Now, for various reasons, the projector will be placed with the lens center aligned to the top of the facade. The projector has lens shift and I will use it but it's likely that I will have to slightly distort as well.
What's the best way to take the photo for content production? From the projector point of view (that is from top to bottom, then distorted) or - as I guess - from the viewer's point of view - which is more "flat" - and then correct the eventual distortion in mad mapper rather than producing distorted content?
Thanks for any advice.
pablitof
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Re: First time building facade mapping advice

Postby ProjectileObjects » Sat Apr 04, 2015 10:46 pm

There are many ways to go about this, but the simplest way is to take a picture that is "through the eye of the camera." By this, I mean, take a picture from where you think you will put your camera, if you are using a short throw lens, then take the photo with a wide angle lens, if you are using a zoom lens then take a picture with something between the 24-70mm range. There is an actual way of calculating exactly what mm your lens should be, but in general you want to get a picture of your entire surface, and don't be afraid to stand back a little further and get more of the building. A decent DSLR should have a high enough resolution that if you get more of the building, you can always zoom in and crop it later for what you need. Then in order to make your graphics, you should realign the photo based on the perspective that you think the audience will view it at, or what most people do if they are not playing around with 3D perspectives is to just straighten the building to give After effects a compensated perspective. This tutorial goes over how to do that in photoshop: http://www.madmapper.com/after-effects- ... -building/

I would recommend experimenting with this based on the visuals you are planning to create, as I mentioned before, choosing a specific perspective for 3D is a little bit more of a science but a basic building mapping isn't bad. On top of that, I think the most important piece of this puzzle is your projector. How much ambient light, the lens, and so on. For this tutorial, the photo doesn't matter as much as the amount of ambient light that was on the building: http://projection-mapping.org/tutorial- ... vertising/

Hope that helps somewhat, it's not bad once you get the basics down, but the variables in setup is where the knowledge comes into play.
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