Enjoying Stereoscopic Content
Introduction
In this short article we discuss how the viewers position affects the quality of the 3D experience. We will also cover some experiments you can try next time you watch a 3D movie and make some suggestions for interactive content.
Parallax
Let's do a quick experiment. Hold up your finger at arms length and look at it with one eye closed. Now swap eyes. You will see that the image each eye sees is slightly different, this is know as parallax.
3D works by sending a different image to each eye. Depending on the depth of a given feature, it will appear displaced horizontally a certain amount when the images are compared.
3D works by sending a different image to each eye. Depending on the depth of a given feature, it will appear displaced horizontally a certain amount when the images are compared.
Correct Viewing Position
In the first diagram we see a viewer sitting at the optimum viewing position. His left and right eyes see the same feature represented by the red and green crosses and his brain tells him in the image is behind the screen plane at the blue cross. The more separation between the left and right features the greater the perceived depth.
Viewing Position affects the 3D experience
If the viewer moves to a different location then the sensation of depth will also change.
Here we show what happens if the viewer gets closer to the screen. The projected image has not changed, the red and green crosses have not changed location, however you can see the 3D affect is decreased (the blue cross is now closer to the screen plane) and the viewers eyes have to converge more which can be tiring.
Here we show what happens if the viewer gets closer to the screen. The projected image has not changed, the red and green crosses have not changed location, however you can see the 3D affect is decreased (the blue cross is now closer to the screen plane) and the viewers eyes have to converge more which can be tiring.
Sitting off to the side
If the viewer moves to the side then a different problem occurs where the 3D begins to distort which may become uncomfortable after a while. A similar problem happens if the viewer is very low compared to the screen.
It should now should be quite obvious that the viewers position plays a big part in how 3D is experienced.
It should now should be quite obvious that the viewers position plays a big part in how 3D is experienced.
Some experiments to try
When watching a 3D movie there are some things you can do to experiment with the 3D. You can switch to 2D simply by closing one eye. This will help you see what you are gaining with the 3D effect.
Another experiment is to remove the glasses. Any part of the image that is sharp is at the screen depth, anything with a double image will converge either in front of or behind the screen depth.
Look to see how much separation there is between the left and right images. You will see that often the amount of separation is really quite small, usually only a few percent of the actual screen width.
Another experiment is to remove the glasses. Any part of the image that is sharp is at the screen depth, anything with a double image will converge either in front of or behind the screen depth.
Look to see how much separation there is between the left and right images. You will see that often the amount of separation is really quite small, usually only a few percent of the actual screen width.
Conclusion at the Movies
We showed that seating position affects the viewing experience when watching 3D. When going to see a 3D movie it is important to get there early and get a good seat. Sitting further back in the middle results in the best experience.
Conclusion for Games
Because games are rendered in real time, it is possible to adjust the strength of the 3D interactively. There are many good reasons for doing this. We can't control where the player sits in relation to the screen but also some people enjoy a stronger or weaker 3D experience. For this reason it is good practice to include a 3D strength slider and let the player adjust the experience to their taste.