Monday, July 16, 2007

Making the 3-D Composite

I'm using After Effects to do the final 3-D mix of the movie, so for those of you who are more video editing/technically oriented, here's an explanation of how I'm doing it:

1. Rendering out right eye/left eye versions of each scene from Poser. Each shot is saved in an AVI file format with a sequential, numeric labeling system - i.e. 0101, 0102, etc. The right and left eye files have identical names but are saved in separate folders, Right and Left.

2. Editing the left eye sequence in Premiere. The project file is saved as FvTWM_Left.pprj. Then, I rename the "Left" folder as "~eft", so when I reload the project in Premiere, it asks "where is the file 0101", etc. By pointing it to the "Right" folder, and since the clips have identical names, it loads up the right eye version of the movie with all the edits to the left eye version still intact. I saved this as FvTWM_Right.pprj.

3. In After Effects, I import both projects. Then, I use the Layer>Pre-Compose feature to flatten all the clips into one layer for each eye, giving me a Right layer and a Left layer.

4. Create a new comp in After Effects which contains both layers stacked on top of each other. To the Left layer, which is on top, I apply the Set Channels filter - taking the Green channel from the Left layer and combining it with the Green and Blue channels from the Right layer. Now, in a perfect world I should be taking the Red channel from the Left layer, but since I wasn't planning ahead when I made the animation, I made certain clothing and prop items red. In the red channel, these read as bright red, but when you look through the blue lens of the 3-D glasses, it reads as black. This produces a flickering effect, known as retinal rivalry.

To compensate for this, I'm extracting the Green channel from the Left layer, which alters the color of the scene and makes the reds appear dark in through both the red and blue lenses. Unfortunately, it also saps more of the color from the movie, so the anaglyph version of the movie looks a bit purplish. Yellows and greens retain their colors ok, but every other color becomes a muted version of itself.

The HQFS (high quality field sequential) version of the movie will be a bit easier to do in this regard, as it simply means applying After Effects' 3-D glasses filter to the Left layer and selecting Interlaced. However, there's another challenge to overcome there, as the movie must run at 29.97 frames per second for the interlaced effect to work, and the movie is rendered out at 24 frames per second. I'm assuming that I'll have to find a way to compensate for problems with audio sync.