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Lightsaber glow: Green screen instead of rotoscoping?

Posted: Thu, 14th Sep 2006, 3:00am

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WithSwissCheese

Force: 220 | Joined: 19th Apr 2003 | Posts: 49

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Hi,

Has anyone green screened the glow of the light sabers?

I'm trying my hand at a light saber duel, and after rotoscoping for a few hours, I'm thinking there has to be an easier / less time consuming way to do this.
Posted: Thu, 14th Sep 2006, 5:01am

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Axeman

Force: 17995 | Joined: 20th Jan 2002 | Posts: 6124

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SuperUser

You mean like, paint the blade green and then use that to key a glow in place? It could work, as long as the blade isn't moving.

Seriously, once the blade is swinging around it blurs too much to get a good key. The easiest and most accurate way is still to rotoscope them in there by hand.
Posted: Fri, 15th Sep 2006, 1:25am

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BackOfTheHearse

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I remember in the days of AlamDV 1, Schwar mentioned offhand that they were working on a sort of motion tracking for the sabers by using LEDs.

Sounded complicated, especially for the DV1 days.
Posted: Fri, 15th Sep 2006, 5:01am

Post 4 of 8

WithSwissCheese

Force: 220 | Joined: 19th Apr 2003 | Posts: 49

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Axeman wrote:

You mean like, paint the blade green and then use that to key a glow in place? It could work, as long as the blade isn't moving.
Yup that's exactly what I meant. Why don't you think it will work with a moving blade? I was thinking it would be perfect for that.
Posted: Fri, 15th Sep 2006, 5:18am

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BackOfTheHearse

Force: 2660 | Joined: 17th Nov 2001 | Posts: 1099

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WithSwissCheese wrote:

Axeman wrote:

You mean like, paint the blade green and then use that to key a glow in place? It could work, as long as the blade isn't moving.
Yup that's exactly what I meant. Why don't you think it will work with a moving blade? I was thinking it would be perfect for that.
He said exactly why....


Seriously, once the blade is swinging around it blurs too much to get a good key.
For example....

Posted: Fri, 15th Sep 2006, 10:41am

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Axeman

Force: 17995 | Joined: 20th Jan 2002 | Posts: 6124

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SuperUser

Yeah, there's a few reasons it won't work well. A major one is the blur when the blade is moving fast, it becomes so transparent that it is barely visible sometimes, making a clean key very difficult. Second, the shape you are replacing it with is not the same shape as the prop blade; the glow extends beyond the edges of the prop, so using a key won't really work anyway. The feathered edges on the lightsword blade are what make this tricky.


Feel free to give it a try, and if it works, great, but all the instances I know of where people hve tried various methods of tracking the blade have been unsuccessful. As far as I know ILM still rotoscopes them frame-by-frame, and if anyone could find a successful way of automating lightsabers, it would be them.
Posted: Fri, 15th Sep 2006, 4:27pm

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WithSwissCheese

Force: 220 | Joined: 19th Apr 2003 | Posts: 49

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My first test came out looking more like a "magical sword".

The bad news is, my key is pretty bad. I keyed on the blades' natural color and used a cheap & noisy Canon ZR60 camcorder for this test.

The good news is, the effect only took me 15 minutes to create and that includes shooting and capturing the video. It looks pretty useable, especially with a better cam and some proper planning & tweaking. The fast moving blade keyed okay. Might be better for a wizard's staff or wand. Perhaps I do a wizard duel instead!!

Notes: I keyed it against a rainbow gradient so that's why it's all different colors.

There are two video files, one starts to look more like a magical flaming sword - especially towards the end. In the other file I tried to tone down the effect to make it look more like a traditional light saber. Anyway here is my first test.

http://goodlightpictures.com/filmandvideo/fx/

Last edited Fri, 15th Sep 2006, 5:23pm; edited 6 times in total.

Posted: Fri, 15th Sep 2006, 4:32pm

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WithSwissCheese

Force: 220 | Joined: 19th Apr 2003 | Posts: 49

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After doing this, I realized I will probably have to key the video twice for multiple colored sabers..

Another option might be to figure out how to automatically make a mask for the blade, like in those iPod commercials with the dancing silhouettes. Hmmm ...

Reviewing the video, notice how the amount of light affects the key. At the beginning there isn't much light on the blade so it has a more subdued effect, but later when my girlfriend holds it out where it's more well lit the effect becomes more overpowering.