I think everyone has seen those shows where they place their host in an artificial environment (such as a studio) and do crane, pans, and any other moving camera work, but still seem to stay in this "fake" world realistically. I have seen some methods of this, such as green screens with black dots, blue screens with black dots, and other screens with colored dots (for tracking purposes). However I have run into a problem, how to chroma out those black spots... I don't want to get rid of my actors hair, or shoes, or sweatshirt, or anything that he could be wearing that is black. So anyone know how to most efficiently track shots like this...

Thanks

-Biblmac-

I'm no expert, but can't you simply just mask out the dots? It shouldn't be too difficult, or maybe I'm missunderstanding your question?

That could be done... never thought of that... it would take an awful lot of time but yea, it could be done... now I feel stupid.

Yeah, you use a garbage matte to remove the dots. Rather than masking each dot individually, You should be able to create a big gmatte that removes them all at once, or perhaps one for each side of the actor.

I read a 'hints and tips' FAQ on some or other tracking software site the other day, they have a couple of ideas which may help.

Have dots on the floor as well as screen, plus maybe some other foreground markers artificially added to the scene, helps with the tracking process - they'll be garbage matted out anyway

Cluster them more densely behind/around the actors head as that's where your attention will be

Use darker green dots on a greenscreen, darker blue dots on a bluescreen etc. They don't need to be a contrasting colour for good tracking software to follow them (especially if you hint the points specifically!), and if the difference is a few shades of green, you can key them out simply

Not tried it myself, but these seem sensible

Pretty much all tracking which requires 3D camera tilts and zooms related to sitting an actor on a greenscreen into a virtual environment is 3D tracking a.k.a Match Moving, done with 3D camera tracking software like PFTrack, Syntheyes or Boujou.

3D tracking is all about parallax - a flat wall of markers is no good, you need foreground and background markers so that the software can calculate the difference in fg/bg movements to calculate the scenes depth.

Though regarding marker removal - usually because you start with a track you have something to attach your rotoshapes (masks) to, then you animate them to turn off whenever a character crosses over them, then where markers are on the edges of actors you paint the edge frame by frame.

It can be pretty laborious, usually when I'm doing marker removal I work towards creating a 'clean plate' which is the shot of the screen with all markers removed, so it looks like a perfectly clean screen - which then gets keyed separately later. Doing it this way means I've got a constant and fast updating reference to how it should look without markers.

Honestly, some marker removal is an effects shot in its own right. It might be worth keeping it simple and having a loose mask around your character and then dealing with markers that creep into that individually.

-Matt

Using black markers (esspecially 'round dots') is probably the worsed thing you can use for tracking purposes.

Better course of action is, if your using a greenscreen, make markers which are varying geometric shapes like triangles, squares, rectangles, right angles etc and place these different shapes randomly over your surfaces and at random angles...Tracking software tracks corners much more accuratly than any circle shapes full stop.....

Make these shapes out of a green material a little bit lighter than your greenscreen material too instead of a colour which most people would use which has a high contrast like blue, red, black etc....

When tracking a shot like this, most if not all tracking packages, on importing your clip to track will allow you to track just the 'Luma' representation of your shot rather than the normally used RGB.

By tracking with the 'Luma' you will be surprised at how the slight difference in the colour of you green markers compared to your greenscreen shows up hugely when your looking at the Luma of your clip....Just like you use 'Key Grading' to better seperate your greenscreen from your subject before keying so you can do the same to your Luma to increase the contrast between the markers and the greenscreen.....Works great i can tell you !

Best of all, as your markers are slightly lighter from your main green the markers will also get keyed out with just a little more push on the slider....

Perfect solution

Wow guys thanks! I will definitely looking into this more as I haven't done this before. Thanks again, I really appreciate this.

We use black gaff tape crosses / X's for tracking on AIDAN 5.