Concept
Project images onto the canal walls to bring attention to the damaging effects of boat wake and turbulence.
Underlying Issue
The canals in Venice are being worn down and eroded by the wake created by the boats that use the canals daily. The wash from the bow of the boats and the wake and turbulence from the propellers transfer energy through the water to the walls of the canals. The impact from the water, in addition to other factors, weaken the walls to the point of observable damage. This presents the risk of sections of the wall collapsing, along with sections of the buildings they support.
Design
A message or image would be projected onto the canal wall. This message could either be present and readable when there is wake, or when there is no wake. By projecting from a shallow angle to the water, the projection will reflect off the surface and onto the opposite wall. When the water is still, the surface would behave much like a mirror or other smooth reflective surface. This would allow the message to be seen when the water is still. When there is turbulence, or the water is otherwise disturbed, the surface becomes an irregular mirror. This distorts the message to the point where it would be difficult to impossible to read.
It should theoretically be possible to project an image that compensates for the wake and therefore is readable only with the wake. With a good camera and a lot of image / video processing, the image could be distorted before it is projected so that the image that reaches the wall meshes together to form something meaningful. While this should be possible, it will be very difficult. First, the computer needs to interpret what the camera sees, determine the effect it will have on the image, and calculate what to do to the image in order to correct for the distortions. This in and of itself is difficult, but the application requires this to be done in real time. The conclusion is that, although this is an interesting idea, it is not feasible to implement in the scope of this project.
An alternative method to display a message only when there is wake, is to have the wake trigger a projection directly on the wall. The projector would be aimed straight at the wall, instead of reflecting off the water. A switch that would be activated by being submerged would then be placed just above the typical water level. This way, when wake hits the walls and submerges the switch, the message would be projected onto the wall. The switch would activate a delay circuit that would sustain the activation command so that the projection is stable until the wake has mostly died out.
The main requirements for an appropriate projector brightness and contrast ratio, to allow it to compete with a non-blank surface. Either of the reflective methods will require a projector with a high resolution, so as to preserve more of the image after reflection. If the image is being projected directly onto the wall, then the required resolution would depend on the complexity of the image.
The image could be a few different things. It could consist of statistics such as cost of repairs, average / typical amount of energy in the wake, etc. It could be clever and/or poetic thoughts and phrases to get people thinking. It could also be a projection of an already damaged section of wall with notes on it, such as the cost and the risk it implies. This could also be done without the image of existing damage, or be projected onto the damage itself.
Indoor Implementation
A wave tank of sorts could be used to simulate the wake. The wake could be produced by a large paddle at one end that just pushes back and forth. Alternatively, one or more propellers could be placed in the tank to create wake and turbulence similar to the boats in the canal.
There could be particles or some other thing in the water to make the currents and turbulence more clear. A projection or physical model could be used to illustrate the effects of the wake in a sort of time lapse fashion.
Interactive Possibilities
The wake generation could be controlled by the visitors. The paddle could be moved manually, or have settings for magnitude and/or frequency. A propeller could be turned or aimed, and the speed could be controlled. Interactions would work better with a physical model, if one could be created that could be reset without too much trouble. Interactive effect on a projection could be managed, with difficulty depending on the level of realism desired in the response of the image.
Concept Art
The first image is what the wall would look like normally. The second and third images are something like how it might appear with just a projection of damage, with the second being more ideal and the third being more realistic. The fourth image is if statistics were added as well.
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Implementation Idea
To implement the "readable when wake:" Use multiple SunSpots in sealed containers anchored in the canal. each would report its accelerometer readings to a central computer (MacMini?) which will then use the data to calculate the wake and adjust the image accordingly.
