This surprised me because I’ve been using the much more “featured” markers that you can find by googling “tracking markers”. I’m wondering if this advice applies to the blender tracking engine?
He also mentions using a normal green laserpen with a refraction attachment, to spew dots alllll over the back of your green screen. I looked up the prices and I would love if this were a realistic solution for the blender engine … would save me a ton of time taping / removing dots everywhere, or trying to set up other stuff. Has anyone tried green laser dots in this way?
Alternatively I was thinking about buying clothespins painted green off Amazon, and either tracking them directly (assuming their shade wasn’t the exact same green as my green screen), or gluing printed tracking markers on them.
Also: What is your experience tracking markers/dots that are only slightly less/more green than your green screen? I used the “Hollywood Camera Work” test plates which use pieces of tape with slight more luminescence / less saturation (or something)… and they seem to work well. What if I printed up those google search tracking markers, but set them to a slightly different saturation of chroma key green?
Also, what is your experience using tracking markers only on 1 plane (the green screen), or 2 (screen + screen floor), as opposed to sneaking a few markers in front of the subject for extra parallax? I’m not sure I can achieve markers in front right now, with my current setup / knowledge /requirements.
Thanks for any advice, and sorry this post is a mess of random thoughts.
All feature tracking engines work the same way, minor differences aside. The logic behind circular markers is that their shape in screen space does not change with rotation, zooming, defocus etc so they are much easier to follow than more elaborate patterns. Plus it is possible to use symmetry matching in addition to pattern, which you can’t do with most other markers.
The fact that google search features lots of complicated markers only tells you that people usually don’t think about such things but simply do what others do, be it reasonable or not.
Markers on only one plane is a difficult situation without additional measurements or survey data because there is no way to deduce the right perspective from them. Result can be inverted perspective, which seems to have low error but is still very wrong. Two planes on the other hand should solve nicely.
So what if I tracked the back wall (green screen) as a plane, then parented my whole Scene to that plane, and inverted the transform or something (depending on whether the result was inverted)?
Otherwise I suppose I’ll have to get at least a few floor markers in there, or perhaps use a prop in front of the actor to track? Any other good tricks?
If it was so easy… inverted does not mean it is simply scaled to -1 on one axis or something like that. You can’t do it yourself unless you have some heavier math behind you and I can’t give any advice on this one as it makes my head hurt.
Use what you can to bring markers out of single plane and spread them out in space.
Use similar color to green screen so that you dont have to roto out the bright orange or pink markers. Tracker will work even with out of focus footage and motion blur all you have to do is get enough contrast to pick up a change. Try placing a dot on a stand in shot for depth, dress it green as well for easier removal.
Thanks for the input, 3pointEdit. I’ve decided to go to the hardware store and bought several 1" washer discs (tiny holes in the middle), and then to the arts and craft store to get some green paint. I’m about to paint the green matte onto the discs, let them dry … then hopefully in a day or two I can attach them to some magnets I bought, through the screen. That way I have the magnet behind the green screen, and the thin painted discs in front, suspended by the force of the magnet.
I find it easiest to just walk around with green painters tape and stick little pieces of it on the greenscreen where necessary. Easy to apply, easy to move around, and cheap.
You should definitely stop using those big chunky markers. Your washer idea sounds great! Matthew definitely knows what he’s talking about, and that article is great. Stick with what he says!
For sure man, thanks! I did a test already and it seems I’ve found a shade of acrylic green that is so very very close to my screen color, it easily keys out, yet is barely different enough to still track in blender. I have more painting to do today but I think this is finally going to happen. Woooooooooot.
Your washer idea sounds great! Matthew definitely knows what he’s talking about, and that article is great. Stick with what he says!