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What is it?
This is an ongoing project that i've been working on to see the potential of interactive stereoscopic installations in examining the perceptual process. I use a setup that i've called a Diplopiascope to investigate this. The Diplopiascope has gone through a few changes but basically it is a stereoscopic viewer that allows the viewer to control the images they are being shown through an analog device.
How does it work?
Stereopsis is the perception of depth through an object being seen with both eyes. Due to the horizontal separation of the eyes, two slightly different views of the same scene are shown to each retina. This information, along with several other cues, is used by the brain to calculate depth.
This effect is simulated in the Diplopiascope by presenting stereoscopic films or images to the left and right eyes via projectors or monitors. The viewer is seated and views the images simultaneously through a mirrored viewing device.
I was interested to see what happens when we present different views to each eye at the same time. This is called binocular rivalry. What happens if we show the same scene at different times? What about greatly different viewpoints of the same object? What if the viewer is put in control of what they see through some physical controls?
This tutorial is more a guide to making the viewing apparatus for experimentation than a physiological explanation of stereopsis itself, and it doesn't go into much detail about how to make stereoscopic films as there is already lots of great information about this online.
Here are two videos of the Diplopiascope being used. The designs are slightly different but the idea is the same.
The videos of the drummer used in the installation above were shot with two cameras from a fixed position. The videos were then looped and projected independently. The videos are viewed through a mirrored viewing device, the left eye being shown the footage from the left camera, the right eye the footage from the right. (In actual fact, the videos are inverted horizontally due to being seen through mirrors. To counter this, the videos were inverted horizontally in the projector settings).
Due to the videos being ever so slightly different lengths (about 100 milliseconds), when looped they become increasingly out of synch. Because of this, while the stationary objects in the video (the drum set, wooden frame, cones, walls, etc.) are seen in crisp stereoscopic 3D, the moving objects (the drummer, people, etc.) will be seen in double. This produces a strange effect as the brain switches uncontrollably between which information it perceives, jumping randomly from the left eye to the right dominating perception. What it looks like is difficult to explain, but the moving objects take on a very strange phantom-like presence in the realness of their solid stereoscopic surroundings. While the majority of the field of view remains fixed in pleasant 3D, the figure of the drummer seems to jump in and out of time frames and consciousness itself.The speed and direction of the videos are controlled by the viewer through an analog device connected to the PCs via arduinos.
There are two speakers, one from each PC, and the audio matches the videos and is also controlled by the dials.
The video above shows a slightly different version of the installation. The principle behind the viewing method remains the same, but one difference is the actual videos being show. In the first example, the videos were shot stereoscopically from a fixed position. In this case, the videos were shot using a mobile camera rig (detailed later). The rig is designed so that it can break apart and come together again seamlessly. By filming along two long pathways of shrine gates, I wanted to see what happened if the left camera (left eye) went down one path and the right camera (right eye) down the other. The left and the right pathways in the video are very similar, but not identical. Would our brains be able to compensate for the little differences in the scenes we see? Would we perceive a unified view of one solid pathway, or would it just give us a headache?
Again the speed and direction of the videos are controlled by dials so the viewer can adjust the images they are being shown. By doing this they are able to play around with uniting and rupturing their visual perception.