Spiderman POV on television

Wednesday, April 30, 2003 8:25 AM
I was watching one of the Travel Channel amusement park shows last night that had some on ride shots of Spiderman. The 3-D did not look blurry like typical pictures of a 3-D movie.

Is there some sort of special lens you can put on a camera to let is "see" the 3-D, or did they do some post production magic to clear up the picture?

Just wondering.

Wednesday, April 30, 2003 9:48 AM
Short Answer: Yes, there is a special lens you can use to not make the picture blurry.

Long Answer: Spiderman's illusion of 3D is created using polarized lenses over a pair of projectors and over your eyes. If you look through one eye, and then switch to the other, you'll notice that objects closes to you seem to noticeably move left and right (called parralax movement) while objects further away move less. When they rendered the animation for Spiderman from the computer they actually rendered 2 frames of every image, one frame which approximates the position of your left eye and one which approximates the right. These images are then projected from two projectors for every screen (all of which I believe are rear projections), one projector for the left eye images and one for the right. Without the polarizing lenses, what you see projected on the screen are just the two images overlapping each other, what you called 'blurry' (though it's not really blurry, it's just double vision)

A polarizing lens works like a screen which only allows parrallel light rays through. One of the projectors gets the polarizing lens mounted vertically |||||| and the other projector's lens is horizontal ====

Without 3D glasses your mind still sees both images. Your glasses, though (or night-vision goggles, as Universal refers to them) also have a vertical and horizontal polarizing filter. The vertical filter prevents that eye from seeing any light projected through a horizontal filter, so now that eye only sees one of the two projected images. Likewise, the horizontal filter on the other eye blocks any light from a vertical filter. Now that your eyes are each seeing a slightly different image, your mind puts them together to see a full 3d world in front of you.

So, in order for the camera that filmed the footage to only see one of the two projected images, all they had to do was mount a polarizing filter in front of the lens.

I could go into much more detail about parralax rendering and viewmaster and 'squinching' (which was Kleiser-Walzak's solution to the problem which consultants said would make Spiderman impossible to pull off) but you're probably all bored now.

Pun is the death of wit.

Wednesday, April 30, 2003 10:27 AM
Thanks for the in-depth description (my head kind of hurts now :) )

I had a general idea of how 3-D worked (the 2 pictures and all) but I didn't know you could actually get a camera to film it. The 3-D images on the show looked just as real and three dimensional as the people sitting on the ride.


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