the following posting is taken from : http://videomappingworkshop.wordpress.com/
The following video mapping workshop was held by Jakob Hronek ( j.hronek[at]chello.nl ) and me Giuliana Dieni ( jules[at]videomapping.org ) at the Dutch Institute for Media Art ( NIMK ) in Amsterdam, The Netherlands.
We are both available to meet people/groups interested in learning the technique. You are welcome to drop us a line, just leave a comment and we’ll get back to you
WHAT IS VIDEOMAPPING
Video mapping uses common entertainment technology in a new, innovative way. It is a technique that consists of projecting video images on buildings, façades, structures or nearly any kind of complex surface or 3D object to shatter the viewer’s perception of perspective. The projector allows bending and highlighting any shape, line or space. It creates astonishing optical illusions, a suggestive play of light and turns a physical object into something else by changing its perception of form.
Video-mapping is quite new and it is flourishing nowadays. The reason of its success is that the public gets somehow emotionally involved in the show. It is not just “another cool visualization”, but it is surprising and exciting and involves physical as well as virtual space.
There are at least two ways of understanding how to make a videomapping projection:
1) Prepare images to project on a surface/façade. Images can be projected as if the building was a huge flat screen. The building itself creates a mask and you will not need to do all the calibration work that video mapping normally requires. Here a sample of a video in alpha channel for a flash project: DOWNLOAD
2) MASKING. As in the word, masking is about creating masks (a sort of opacity templates) with the exact shape and position of the different elements of the building, space architecture, 3D object etc. On those masks, or in the space between this masks, is where the video is going to be projected, using a simple alpha-channel technique.
HOW TO MAKE A VIDEOMAPPING PROJECTION
- HOW TO VIDEOMAPPING -
The most important thing you need is, obviously, a video projector. The video projector need to be powerful if the area to cover is that of a building. For little objects and for room projection you need a basic 5600 lumens so to have a good definition of your work. But you will need up to 20.000 lumens to produce a clear, accurate image on a big surface and/or from a long distance. Of course there is more to be considered, like the kind of lens you need for a building projection.
Some characteristics of a video projector for a video-mapping project are:
- 10.000 Lumens min. (on a building surface)
- A Remote control ( stupid to say, but important in some cases )
- Lens less wide as possible. Do not use a fish-eye lens the curvness will make it impossible to match the object.
- Resolution of min1024 x 768 pixels
You will also need a photo camera. You should be able to adjust the lens in order to match as much as possible the lens of the video projector. In this case you might need a camera with a good lens. This is a crucial point, we will explain later on.
Video mapping is not a cheap activity. Projectors are expensive equipment: a 20.000 lumen projector can cost up to 100.000€, and the rent can be often an obstacle. This being the case, it would be a good idea to contact a company or organization who can sponsor your project and cover all the expenses derived from the rent of the equipment. The real challenge comes when the artist is able to do something beautiful, artistic and professional, and at the same time satisfy the client.
VIDEO-MAPPING IS GREEN AND CLEAN
Indeed: apart from the unavoidable waste of energy necessary to project the images, you don´t need any kind of paint or chemical component to modify the building/space/object. Another advantage of video-mapping is that it does not damage in any form the building you project on, and once the magic is, everything remains as it was.
MANAGEMENT OF A PROJECT
1)PREPARATION Best way to work is next to your video projector but that is not always possible. In any case there are different ways to go. Resolution approach: you have to consider the specs of your video projector and match your project with the maximum resolution of the projector. Video approach: you want to set your work/project on PAL/NTSC standards ( for example 720X576 ) or HD in case you want to work with an HD projector.
2) THE BLUE PRINT Next thing would be in most cases to take a picture of the building or the object you are going to project on. This image will be used to get a layout to create masks or 3D references for your projection points.
This is the most delicate part of the process. You need to use a camera lens that has the same ratio as the projector lens. Then you place the camera beside or on top of the projector lens, and make the photo: what is important is that the camera lens is in exactly the same position as the projector lens.
Here you can see different examples of succesfull and unsuccessful photos:
In ‘map picture number 1′ and ‘map picture number 2′ we can see 2 examples of a bad camera positioning . These are the pictures Olga Westrate took from a different angle from the video projector lens. That camera angle of view is only critical with very wide and very narrow angles. So you only need to be accurate in selecting a camera lens if you are doing very short or long throw projections
3) SETTING UP
Video-mappers, like vampires, work at night. Or, if that´s not possible, they try to make their projection area as dark as possible. They are patient creatures and their first commandment is: setting up consumes a great deal of the time.
First of all, you have to place the projector exactly in front of the object you want to project on. Side projections are very unlikely to work.
You might need a distance measuring laser tool and can also use a bubble level to make sure that the position of the video projector lens is perfectly horizontal and that matches the camera lens position. Once the video projector is placed, and the cables have been carefully taped and protected, you can start your testing. It is also important to know that a projector is very sensitive to vibrations and weather conditions. You don´t want to see an ugly jittering image right in the climax of your show, and likewise you need to think about the variable weather conditions, so you should take measures and find a suitable stand and rain protection for the projector.
Even if she was using a good camera in picture number 2 and a wide angle one from her phone in picture number 1 the object is not matching the beamer lens throw.
In map picture number 3 the picture highlighted in red shows a good positioning and its matching our guide picture. It is a simple calibration made by taking a picture of the object and projecting in on the top of the object.
Here Richard Neef used the same position of the beamer and he was using a simple digital camera.
3) CALIBRATION OF THE PHOTO
Once we have the right position and the picture is calibrated, we want open a photo editing software like Photoshop, or GIMP if you like open source software, and we set the size of the photo to our projector´s resolution (in our case, 1024×768 px). Then we set the view to 100% and we project the image back into the object. You will clearly see if the photo is calibrated (every element in the photo matches the real building), and you can make small retouches so that everything matches perfectly.
This is important if your work uses the same formatting for the whole project. If instead you’ll convert it to video is unlikely that your video format ( 720×576 etc.) will match this resolution. Please convert the picture format to your final project output.
4) CREATING THE MASKS
This you can do with any program you are familiar with: After Effects, Illustrator, Photoshop, Flash, Cinema 4D… there is now VJ software that allows you to create masks “on the go”. You “cut out” de different elements of the image and create masks (templates) in different layers, one for each mask. There are hundreds of tutorials in the web about how to create masks, here some of them:
Once you have your masks, you export them separately. We get something like this:
Now the real fun begins. We have our masks, and it is time now to decide what we are going to do with them. Video-mapping is not restricted to any particular software at all. You should just use the program you use for your animation/film/video stuff, like for example:
-Adobe After Effects
Just use your creativity, make a little plan of what you want to do and… we´ll see the results in the next lesson!
This week at work, I decided to video map my toaster. For those that don’t know, video mapping is a technique that allows you to wrap a projection around a 3D surface. It’s often seen on buildings for advertising purposes, and weird geometric shapes in art galleries.
I spent about two hours the first day making the map. I did this by taking a photo (top) of the toaster from the angle of the front projector. Then I traced the photo in Flash and began projecting the flash file on the actual toaster. I adjusted the image until it was aligned, assigning each section a different color to make it easier to see where things weren’t lining up.
On the second day I made the effects for the toaster. It took about 4 hours, and I had a lot of the footage already. I imported my color coded reference image into After Effects and used it to line up the video clips I wanted in each section.Then I rendered the movie files and imported them into flash.
On the third day I made corresponding background movies and imported them into a different flash file so I could sync the timing of the front and back projections.
I used a second computer and an ultra-short-throw projector mounted above the toaster for the background projections.
The whole project took 3 days, and in the end I had enough footage for this: