Excellent Article on Stereo 3D Volume and Focal Length

Phil McNally of Dreamworks Animation has a very impressive article that is a must-read if you are involved in stereo 3D shooting or effects. His post deals with issues of roundness and stereo depth volume, and most importantly, the interplay of camera lens focal length upon “cardboarding” and perceived volume.

What’s most impressive is that the article captures the interplay of camera lens’ focal lengths, the seating position of the viewer in the theater, and volumetric perception — and does so visually. There are some rather large quickTime videos embedded in the page, I would urge patience (load the page, have a Martini, and come back). This is excellent training material for would-be stereographers. I think this is probably the finest example I’ve seen to-date that explains the issues in terms of visual intuition.

To quote Phil: “There are several large movies as I wanted to keep the anaglyphs looking clean. The page is about 150mb in total so be patient.”


I have only one minor quibble: while stereographers shooting live-action with real, physical cameras will encounter these limitations, in an animated CG pipeline there is no reason to make your “virtual cameras” behave like “real cameras”. In a CG pipeline, the laws of physics are quite fungible, hence “multi rigs”. This quibble detracts nothing from the quality and facts of his article, however.

Nevertheless — there is a way to apply this knowledge to fix “flat/cardboarded” shots captured by real, physical 3D stereo rigs with extremely long focal lengths… a subject for my next post.


~ by opticalflow on July 6, 2011.

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