Although Marvel Studios wanted Kenneth Branagh to direct Thor in 3D, Branagh refused on the actually pretty reasonable grounds that he didn’t feel comfortable shooting such a large-scale production using techniques he wasn’t familiar with.
So the Thor 3D release at the cinema and now on Blu-ray is the first one covered in this feature to use 2D to 3D conversion.
And actually, the results are rather better than those seen with most converted 3D films. Some scenes use 3D to really quite spectacular effect; the Destroyer’s attack on the town being a strong example.
However, while some scenes work well, for most of the time it’s pretty obvious that this is only a 3D conversion. The sense of depth in the picture often looks like a series of flat layers or planes rather than a natural 3D space. The effect is kind of like the parallax scrolling layers early computer games used to deliver a sense of depth.
Not surprisingly seeing this sort of effect can distract you from the film, so again, overall we’d recommend that you stick with the cheaper 2D version.