Stereography is an exact science that has been studied by several authors over the last 180 years, although we now face a new challenge. The representation of the human figure in a stereoscopic equidirectional environment will be affected both by equidirectional projection and by the effects derived from steriopsis.
Steriopsis is an effect that occurs at the neuronal level. The optic nerves of our two eyes transmit to our brain two almost identical images, but captured with a different parallax. The steriopsis acts by creating a three-dimensional model, which will be affected by different factors: the parallax itself during capture, the adjustment of the parallax during postproduction, the interaxial distance and the aperture of the optics used. Not forgetting that these effects must be combined with the spherical projection.
The objective of this study is to expose the parameters necessary for human figures to be represented in a virtual environment, while maintaining their proportionality.
This study will be applied to the insertion of human figures in computer-generated scenarios, and will also be applied to the construction of humanoid avatars in VR video games.
Although our objective is the visualization of these effects in the Head Mounted Display’s, type Oculus, we will use the system anaglyphs (Red/Cyan) for its comprehension.
Before starting it is necessary to check the stereoscopic visual acuity. If it is possible to determine the difference of distances at which the different figures are represented, the steriopsis is correct.
Size variation due to parallax adjustment in post-production.
Click on the photos to enlarge them
These three photographs are exactly the same. The only difference is the parallax setting. In the first picture we see that the model tries to get out of the window. A negative parallax effect has been applied to the model’s face. In the second picture the zero parallax has been adjusted to the model’s ears. So they are represented in the same plane as the frame. In the third picture the parallax has been positively adjusted, so that the figure is behind the frame.
As we can see, the parallax setting will allow the model to move forward or backward.
The effect of steriopsis:
Now let’s take a closer look at the fact that as the model gets closer or farther away, its size varies. In the first photograph, where the negative parallax effect is more noticeable, the model appears much smaller than in the third photograph, where the parallax is positive.
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