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Roto vs Motion Blur!; A Quick Review

Rotoscoping could be one of the least desirable things to do, but it is nevertheless one of the important steps in preparing a shot for the final comp. Personally I find it ok, sometimes it’s exactly what you need! to just seat back, listen to some music and get on with it! but in occasions when the process gets very long and days passes by with making just a little progress, you start to feel a bit anxious!

Many skills are required to become a good roto artists, I couldn’t imagine I would be excited to do a roto task because I knew this time I have new challenges! but it happened! and as far as there’s something new to learn, there’s joy.

One of hardest things to tackle in a roto work is getting the motion blur right. When you have something like that (image above) to roto, suddenly there’s no visible edge, the direction of the motion could be misleading as the direction of motion blur is not always the same(depending on the shutter speed/angle), so it’s important to understand the tools you are working on.
Some companies have developed their own in house tools (e.g. Noodle in Double Negative) , but I believe Silhouette is the most commonly used and industry standard package. Amongst it’s good futures, calculating the right motion blur is extremely useful, there’s a little trick though! To create the motion blur accurately, Silhouette calculates the distance that the points travel in each frame. It’s very important to keep the point consistent meaning if a point for example is on the tip of a finger, it should stay there for the entire frame range.

In Nuke, apart from the default motion blur options inside the roto node, you can control the motion blur with feather quite easily but this sometimes involves you in doing a lot of frame by frame motion blur modifications. There  are so many tricks you can work out to deal with this of course (e.g. applying motion blur node, or Motion Blur 2d by tracking the movements) and create the motion blur on the mattes, however, an easy solution would be using “TimeBlur” which is very similar to the motion blur settings in Silhouette. It takes a little time getting used to, but it gives you motion blur based on the shutter speed. (you may apply as many as TimeBlur nodes needed to get the best result)

* don’t even think about doing roto with a mouse! get yourself a tablet.

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