While more and more 3D-capable TVs and other displays are appearing, as are Blu-ray players that support the new Blu-ray 3D standard, the quantity of actual 3D material remains rather limited.
But an increasing number of TVs try to address this by providing special video processors that convert 2D to 3D. This is not the only conversion that takes place. This sometimes also happens in the movie studios.
It takes a while to make a movie, so some movies were made the regular way, but at some time prior to release it was decided that a 3D presentation would be appropriate, so a number of these were digitised and then run through a 3D processing facility. Converting 2D to 3D is not an easy thing to do.
Current 3D display technology works by showing your left and right eyes slightly different angles on the action. That means your right eye sees a little more of the right side of an object than your left eye does. More importantly, it also means that your right eye sees a little more of the background behind the right side of a foreground object than your left eye does.
And the same happens on the other side with the left eye.
If you only have a regular ‘flat’ film, how do you create two eye views that reflect those differences?
Well, the computer essentially cuts out what it judges to be the foreground objects, and stretches the background a little, as required, for each eye’s view in order to hide some of it behind the object, appropriately for each eye.
This is all very tricky, but it seems to work.
The harder thing is judging what is in the foreground, and what is in the background. The algorithms have to make assumptions. Things that are in the foreground are more likely to be in sharper focus, to be larger, and to be towards the middle of the frame or below the centre line. These simple rules are not fool-proof. In the opening moments of The Searchers, a 1950s Western with beautifully sharp presentation on Blu-ray, a rider is approaching a foreground character.
Using the rather good 2D to 3D conversion facility in a new model TV, the rider, the close character, and the low ridge perhaps ten of metres behind the rider all look to be pretty much the same distance away from the camera, as judged by the 3D process. A further away ridge – one that is perhaps a hundred metres back, looks to be only slightly behind the closer ridge. Distant – miles away – monumental mountains hover there against the blue sky, seeming to be much further away than all the foreground stuff, yet still seeming not quite back at the level of the sky, which is how they’d appear in real life.
In fact, there is no way that automated 2D to 3D conversion can be performed perfectly with some automatic system.
With human intervention though – apparent disappointments such as Clash of the Titans excepted – impressive results can be achieved. Piranha 3D isn’t much of a movie, but it was shot in 2D with the intention right from the start, say the movie makers, of being released in 3D. Apparently the 3D camera rigs would not have worked very well in their environment.
And the truth is, say what you like about the movie, the 3D works very well indeed.
Likewise, James Cameron – the current title-holder for the best 3D movie out there – is releasing his 1997 classic Titanic in 3D next year. I think we can be confident that every single frame of this release will have been closely controlled in its 2D to 3D conversion.