Accurate Projection Mapping

Accurate Projection Mapping..

There are 3 main ways to do accurate projection mapping.

The very expensive way - a LIDAR laser scan  of the building and a 3D based media server such as Disguise

The difficult way - drawing onto the building through the projector with an app like photoshop - usually means being outside all night

and then there is the way I do it..

Work from a photograph taken from the projector position.

I invented this approach myself back in the days when I used to do building projections with slides and needed to get it right first time every time. Sometime in the early 1990s if I remember rightly.

So here’s a brief walk though of the latest mapping project that I did for EMF onto a town hall in the UK

First, photograph the projection surface from the projector position

To get this photo, I had to put the camera on a light stand and wind it up to 20ft - the final position of the projector on a scaff tower in the square..

I then pop the photo into photoshop and make a template that acts as a map for all the content and I also use to generate a line up for the individual projectors. In this case using a 1920 x 1080 pixel template that matches the native resolution of the projector.

Then you just do all the content - I drop the .psd template into after effects and do everything there..

finally I generate a lineup - using the original photo + find edges, invert & levels. which is projected back onto the building to bring the projected image into a perfect fit for the actual building.. 

Of course there is bound to be a small amount of final adjustment but it’s usually just an inch or so off - all down to manufacturing tolerances in projector lenses, accuracy of projector placement and so on. I use Resolume Arena for playback. On this particular job the lower centre was off by around 4" so it just needed a tiny nudge in advanced output. If you can't afford Resolume, take a look at Qlab, which is free so long as you don't save, or you can rent it by the day.

here’s the end result..

projection 3 x 18k lumens Christie HD projectors
Playback Resolume Arena

Here's my original how to vid from 2007, ignore the bit about comparable lenses.. seems I was mistaken about that bit of the process..

Have fun