Video Systems in AV
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Projection Mapping: Basic and Advanced Theory - Part 3
So far we’ve covered the following:
Origins of Projection Technology
Projection Evolution
Projection Screens
LCD, DLP, LED and Laser Projectors
In this article we look at the following:
Basics of Projection Mapping
Origins
What is Projection Mapping?
Common Methods used
How to do Projection Mapping
Projection Mapping Origins
Although the term "projection mapping" is relatively new, the technique dates back to the mid-20th century.
Josef Svoboda, a Czech scenographer, debuted Lanterna Magika at Expo 58, the 1958 Brussels World Fair.
Lanterna Magika was a live performance that featured singers, dancers, and musicians performing against a backdrop of projected film footage.
Günther Schneider-Siemssen was a German set designer, who coined the phrase, "painting with light”. He used Pani projectors to create large-scale projections for operas.
What is Projection Mapping?
Projection mapping is a projection technique used to turn objects, often irregularly shaped, into display surfaces for video projection.
The objects may be complex industrial landscapes, such as buildings, small indoor objects, or theatrical stages.
Using specialized software, a two- or three-dimensional object is spatially mapped on the virtual program which mimics the real environment it is to be projected on.
The software can then interact with a projector to fit any desired image onto the surface of that object.
The technique is used by artists and advertisers who can add extra dimensions, optical illusions, and notions of movement onto previously static objects.
Projection Mapping Methods
After the object which will be projected on is chosen or created, software is used to map the corners of the video to the surfaces. First, one must choose the images or video to project. Each video is then placed on its designated surface.
Alternatively, one may map the entire scene in 3D and attempt to project and mask the image back onto its framework. The next step is masking, using opacity templates to actually "mask" the exact shapes and positions of the different elements of the building or space of projection.
In 3D mapping, coordinates are defined for where the object is placed in relation to the projector. The projector's XYZ orientation, position, and lens specification result in a determined virtual scene.
Adjustments are commonly made by manually adjusting either the physical or virtual scene for best results. Large projectors with 20,000 lumens output or greater are used for large-scale projections such as on city skyscrapers.
Due to the scale and brightness some projects require, often large arrays of powerful projectors are combined into a single image through a method known as "edge blending" or "stacking".
The result is a much brighter projection that maintains its seamless look. This technique is used for most large projection-mapping shows, and requires skill and patience to be set up with specialised software.
For smaller productions, smaller, lower-output projectors are sufficient. In most cases, a 2200-lumen projector is adequate for projections under indoor light or theatrical lighting.
Video mapping software can be used in projects like these, though Adobe Photoshop, Adobe After Effects and other packages can also be used by creative artists. Extensible open-source software frameworks are also available.
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| Video projection mapping front façade of a building |
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| Projection Mapping Test Grid |
Choosing the best projection coverage
Before we dive further into the realm of lux and lumens, let’s tackle something else first that is equally important to understand if we want to find the best possible projector configuration for our mapping project!
There are two ways to create projected imagery on the surface of our choice, and these will influence the final projector selection (in terms of brightness, resolution, point of projection, number of projectors, etc).
These two approaches are what we call single and multiple raster (also called array).
The difference between single and multiple raster
With a single raster you use a single projection point for the entire image area, then overlay additional projectors that add brightness until you get the desired optimal result that works best in the given environment.
This single raster approach requires careful alignment of all the projectors, but it is much simpler than the multiple raster solution that requires edge-blending.
With the more complicated and complex multiple raster configuration you project an array of images that are blended together into a single image, and this results in a higher image resolution.
This edge-blending, or soft-edge masking of the overlapping images is more advanced than the single raster approach, but with the right projector that should not be an issue.
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| Single and Multipoint Projection Source: Panasonic |
How can Projection Mapping be used?
Projection mapping can be used for advertising, live concerts, theater, gaming, computing, decoration and anything else you can think of.
Specialized software or just some elbow grease can be used to align the virtual content and the physical objects.
The dynamic nature of projection mapping has revolutionized the way we visualize and interpret data.
Beyond static graphs and charts, projection mapping provides an immersive experience, turning any surface into a canvas for vivid representations of data-driven narratives.
Choosing the right projector lenses
It is imperative to pick the correct projector lens for all projectors, and by going with the best projector manufacturers you will have a range of high-quality, all-glass lenses for your mapping project.
The full range of lenses are the key to flexibility in the design and installation of the setup.
Throw ratio is our key parameter here, or in other words the distance measured from the end of the lens to the projection screen, divided by the width of the image.
The minimum required throw distance is defined by the lower end of the focus range of the lens.
In order to see what options you have, and to properly calculate the specifications for your setup, we suggest using an online guide.
Online Lens Calculator example: https://lenscalculator.barco.com/
Online Throw Distance Calculator example: https://panasonic.net/cns/projector/calculator/tdc/
How do you do projection mapping on a building?
Step 1 : Laser scan the building
The fundamental difference between 2D and 3D projection mapping is that 3D projection mapping accommodates the shape and contours of your projection surface. If up-to-date 3D CAD’s are not available, then laser scanning the projection surface will provide the template to start the 3D process.
The laser scanner used to create the 3D map of your projection surface is a common tool used in the construction industry and, because the hardware is highly specialised and expensive, most AV companies will rely on a professional scanning company to provide this service and then construct the 3D model.
Laser scanning is normally done about a month before the event and can take anything from 4 hours to 2 days to complete – depending on how big the surface is and how complex the architecture of the object.
In the case of 3D mapping of a building, the scanning requires unobstructed views of the structure and is often done in the early hours of the morning, when there’s likely to be less activity.
At the end of this step, the AV company will have a 3D CAD drawing of the projection surface that is accurate to within 1.9 microns – which is less than 2 millionths of a meter!
Step 2 : Apply the audience perspective
The audience’s position is an important consideration when creating content to project onto a 3D surface – the content needs to be optimised for their perspective to ensure the best experience. Eg : if the audience is going to be looking up at the images projected, then the video would be filmed from a low angle to emulate their point of view.
Your projection mapping specialist will convert the digital architectural drawing of the projection surface into a design format and then identify a position which will be used as the audience perspective reference. This is handed over to the content creators.
Step 3 : Create the content
Content might include graphic animations, video footage or a combination of the two – created for the best experience based on the audience perspective. The final content is rendered into movie files and returned to the projection mapping specialist.
Step 4 : Preview
Everything is now imported onto media servers where the flat movie files are applied directly onto the texture map of the projection surface to see how the content reads when played out on the building’s topography.
Virtual projectors are then added to map out their ideal position, rotation, size, lens ratio, projection distance and lens size.
Step 5 : Adjust for real life
The projection mapping specialist now needs to marry the digitally-recommended projector positioning with real life limitations. Ideally all the projectors used in a projection mapping project should be in line with each other and equal spaces apart, but circumstances at the venue seldom allow for this.
Adjustments will need to be made using a combination of the projectors warping facilities and the media server’s mapping controls Detailed projection locations are plotted out in the media server with a 10-15% overlap for blended projection, which gives a seamless edge between images displayed from different projectors.
Here’s a link to Panasonic’s Projection Mapping Handbook
Quick Recap
So far we’ve learned the following:
Projection mapping is a projection technique used to turn objects, often irregularly shaped, into display surfaces for video projection.
Objects which will be projected onto can be anything from a car to a building
Specialised Software is used to map the surfaces that will be projected onto
Single and Multi Raster methods for a single or multiple projectors
It’s very important to calculate throw distance and to select the correct projector lenses
Next Up…
We go through Rental LED Screens
Differences between Rental and Installed LED Screens
Pixel pitch
LED Screen Controllers
Pixel Mapping
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