If You Build It, They Will Come.

Tuesday, October 28, 2003

I want to talk about rotoscoping.

Allow me to give a brief overview of this project. As I'm sure anyone who reads this site knows, I am in the middle of shooting/editing/producing a feature length independent film. In this film there is a dream sequence where the main character is involved in a "lightsaber" duel. The duel itself has already been shot, edited together sequentially, and has ended up looking pretty nice. The "lightsabers" themselves were props built or bought using old toys and dowls marked with different colored electrical tape so I could see where they were when it came time to do the rotoscoping.

Rotoscoping is the process where you draw an image over a filmstrip frame by frame. It's essentially a mixture of animation and tracing. Here's how it works. For every frame of this duel, I have to draw a line over the spot where the 'lightsaber" is on a second layer. To explain this, imagine a picture of the Mona Lisa. Now imagine covering it with a piece of tracing paper, and drawing a mustache and glasses over her face. When you take the paper away from the painting, all you have is the mustache and glasses.

Now this entire second layer of lines I've drawn over the original filmstrip is nothing more than a bunch of white lines that on their own seem to make no sense. I then make a copy of that layer. On the copy, I add a blur effect, to make the line look softer. I then make a copy of the blurred lines, and blur them just a little bit more, and add a color. The trick is of course that I can only do one blade at a time if I want them to be different colors, so for any shot that has both "lightsabers" in it, I have to do the whole process from start to finish, twice.

Now that I have my three layers, I condense them back down into one image. Imagine taking both sheets of tracing paper, and the original Mona Lisa, and putting it on a Xerox machine. The resulting copy you get would show the Mona Lisa sporting a new moustache and pair of glasses that you could not remove. That condensed copy of the 'lightsaber" then gets turned back from a filmstrip format, which looks like one giant picture, to a movie format.

The reason this is such a pain is that my camera, as is the case with most digital video cameras, captures at 29.97fps. Meaning that for every second it's recording, it takes about thirty indiviual pictures, or frames. The duel itself is 1:41.5 minutes long, or 101.5 seconds. This adds up to a grand total of about 3,450 individual frames, the majority of which feature both blades, meaning I have to do them twice. Timing myself, I found that it takes on average, including the blurs, about twenty minutes of rotoscoping per second of film per blade. Meaning fourty minutes per second anytime there are two blades. We'll say that the average is 35 minutes per second, as three are shots that have only one or no blades in them, but they are few. Thirty five minutes per second, with 101.5 seconds of film means 3,352.5 minutes, or just about 60 hours of drawing lines, of course not counting times I screw up or my computer just decides to crash. 60 hours of work for a scene that is just over a minute and a half long. Not to mention the hours of adding in all the sound effects and foley.

That is dedication.


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