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Swords can be modelled as "oriented bounding boxes" or OBBs. OBB/OBB collision has been part of the toolkit for years and is not computationally complex. The computation of sword/sword collision is not the hard part. The gameplay mechanics to make it fun, are.

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Actually no. Thin, quickly rotating objects are an area where a lot of collision detections libraries fall down - the simpler algorithms just look at the position of the objects each frame, and two swords can easily pass through each other in the time between frames.

The problem is called tunelling, and though there are some features to deal with it, there aren't any ones that are simple, reliable and cheap.

Why wouldn't the blended ray+physics technique described in the article not work? I am imagining projecting a bunch of rays from the blade along the vector of travel each physics tick and using that to determine if a collision will occur during that tick.

I've never tried to implement anything like that, so I am curious where that might Fail.

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