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3D tracking green screen markers

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James Strecker
3D tracking green screen markers
on Dec 19, 2016 at 3:47:07 am
Last Edited By James Strecker on Dec 19, 2016 at 3:51:51 am

Hello. I apologize if this has been asked here before, but I've been Googling this for hours and have come up with nothing. I'm hoping someone here can help.

I have painted a giant green wall for green screen purposes, and have been trying out various techniques for 3D trackers. Recently I happened upon several behind-the-scenes screenshots from Hollywood films (see below) where they use orange tracking markers, so I bought some orange tape and have been applying my own. However, After Effects is doing a terrible job picking them up. I've even tried cranking the heck out of the contrast, pre-comping, and then tracking, and still no good. It's like it doesn't even understand they're there. They're pretty bright and definitely don't "blend in" with the green wall, so I don't know why this is happening.

I have a shoot with an actor from out of state in a couple of weeks, and I need to make sure this is resolved before then. I've already considered that I may just need more tracking markers, but since it's currently not picking up even the 3 I put up there, I don't want to waste my time putting the rest up if it's not going to work. Below, I've provided a link to my footage and final product. I was able to track the garbage cans and floor in this particular shot (it picked THOSE up...) so I could salvage it. But I'm going to be doing shots where the background is entirely the green screen and tracking markers, so I need to make sure it will work.

Thank you so much for any help you can provide.

Tracker examples:
http://img.gawkerassets.com/post/4/2013/02/vfx6.jpg
https://www.fxguide.com/wp-content/uploads/2012/03/CTY_012BEFORE.jpg
http://www.enfilme.com/img/content/bc7524619489a2a797f71d5343ac75c136.png

My footage:






James Strecker
JTS Entertainment
http://www.youtube.com/JTSEntertainment


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Simon Ubsdell
Re: 3D tracking green screen markers
on Dec 19, 2016 at 9:33:09 am
Last Edited By Simon Ubsdell on Dec 19, 2016 at 10:52:22 am

An effective way of isolating the tracking marks here would be to use your keyer to composite the image over, say, a white background (or you could simply display the B&W matte view) and that way the tracking marks will really stand out and be easy to track.

However, it's far from ideal (!) to try and do a 3D track off three closely spaced tracking marks all on the backing since you are providing barely any parallax for the tracker to get to grips with. At the very least, have widely spaced tracking marks, but preferably also have trackable objects on a plane (or planes) that isn't the background. It is essential to give the tracker enough parallax in the shot that it can solve the camera position.

Simon Ubsdell
tokyo productions
hawaiki


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James Strecker
Re: 3D tracking green screen markers
on Dec 19, 2016 at 5:12:13 pm

Great, suggestions, Simon. Thank you. Like I said above, I didn't want to spend the time putting a bunch more tracking markers up if it wasn't even detecting these 3, but you make a good point. I will also try the white background keying idea.

Thanks!

James Strecker
JTS Entertainment
http://www.youtube.com/JTSEntertainment


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Greg Gesch
Re: 3D tracking green screen markers
on Dec 19, 2016 at 10:41:45 pm

Hi James, the sample tutorials on this page are excellent and should help:
http://www.hollywoodcamerawork.com/visual-effects-for-directors-sample-clip...


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James Strecker
Re: 3D tracking green screen markers
on Dec 20, 2016 at 5:19:10 am

Thanks, Greg. I've already watched all of those videos. That's actually how I got up to where I am currently. They describe actually painting tape to be slightly lighter or darker than my original green, but I felt that was too time consuming and a waste of money. I instead opted for the orange tape after I saw it used theoretically-successfully in big budget Hollywood films. Just having a bit of trouble so far getting it to work right. I haven't tried the suggestions above yet, but will soon.

James Strecker
JTS Entertainment
http://www.youtube.com/JTSEntertainment


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Simon Ubsdell
Re: 3D tracking green screen markers
on Dec 20, 2016 at 2:14:21 pm

3D tracking with green screens is always a bit problematic since the depth information of the scene is almost entirely lacking, which is why you really need tracking markers placed at varying depths from the camera for the best results. If the tracking marks are only on the green screen backing itself there is almost no parallax to speak of.

You've already noticed that you can get a track off things like your trashcan which are not on the same plane as the backing. It's pretty easy to set up depth markers, and typically ping pong balls mounted on sticks work well.

You might also ask yourself if you really need 3D tracking for your project and whether you can make do with (Mocha) planar tracking, which would make life a lot easier.

Simon Ubsdell
tokyo productions
hawaiki


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