My room is 3.6m x 3.6m. Is it worth trying to mocap?

Greenlaw · **Posted:** Wed Nov 09, 2016 3:15 pm

If the image is accurate, I agree, 170 cm looks promising. It's quite a bit higher than the recommended height and angle for a Kinect sensor but it certainly can't hurt to try.

Let us know how it works out for you. If this doesn't work (likely ground plane issue), split the difference and see how that goes.

FYI, even though I've been focused on using the near 180 degrees dual setup lately, I'll be switching back to the near 90 setup in my next session--similar to what you're doing. What I learned a while back was that, even though near 180 can minimize occlusion errors, near 90 allows you more capture space in a tight room. Just thought you'd like to know that.

Good luck!

dzonatan · **Joined:** Mon Oct 31, 2016 1:54 am **Posts:** 15

Right now I have a different problem that rather upsets me.
I went out of my way to get myself a green screen in hopes to cover up yellow spots I had in the corners but for whatever reason they are still there:

http://imgur.com/a/UU1fP

Seems Im going to have to get a blanket instead.

dzonatan · **Joined:** Mon Oct 31, 2016 1:54 am **Posts:** 15

Background elevation however removes yellow entirely.

http://imgur.com/a/BYSAF

Not sure what to think anymore.

Greenlaw · **Posted:** Thu Nov 17, 2016 6:36 am

dzonatan wrote:

I went out of my way to get myself a green screen in hopes to cover up yellow spots I had in the corners but for whatever reason they are still there:

Seems Im going to have to get a blanket instead.

Hmm...sorry to hear you went through all that trouble. Specifically, a green screen will do nothing for iPi Motion capture. A green screen is used for chromakey shooting for visual fx and it isn't particularly useful for iPi Motion Capture. (See note at the end for why I used to have a green screen in our garage.)

If you're trying go block light, you need black-out material, which you can purchase in fabric stores like Jo Ann. It's pretty cheap and it's designed to do exactly what you're describing. Here's an example:

Blackout Fabric

Black-out fabric can specifically help Kinect capture because UV pollution from outdoor lighting can affect the quality of capture data. I used this fabric to make a cover for an SLA printer to help block-out UV light, as well as dust, from entering the housing and it's been very effective. But for Kinect motion capture, I normally avoid shooting in the daytime altogether because our living room has many windows and I can't block all of them.

Roclon and Duvateen are some common brands for light blocking material. I think Roclon works fine and it's a whole lot cheaper.

Alternatively, you can get roll-up shades made of black-out material at hardware stores like Lowe's or Home Depot. We got a pair for my daughter's bed room years ago when she was a toddler so she wouldn't wake up so darn early in the morning, and they really worked well for that! Nowadays, I use black-out shades in our computer room to eliminate outdoor light when working on color sensitive projects. The kind I got was designed so you can easily cut the roller down to fit your window. I don't recall what they cost but I know they're a whole lot cheaper than black-out curtains. Here's an example of one kind from Home Depot:

Bali Cut-to-Size White Cordless 12mm Blackout Vinyl Roller Shade

Seeing the pics of your room, the shades might be more convenient for you?

In some of my early iPi videos (like from five years ago,) you might have noticed I have a green screen environment but this is because I occasionally needed to shoot chromakey footage for my work. The fact that I had a green screen in the room is mostly incidental but it did hide a lot of the clutter stored along the wall, which could affect PS3 recording at the time. Plus, it kinda looked cool. :)

The green screen there would have made no difference for improving Kinect based capture though. And light blocking fabric wouldn't have mattered either because the garage doesn't even have windows.

Hopefully, your green screen won't go to waste--they're actually very useful in vfx production. Coincidentally, I am restoring our green screen later this month to use for our 'motion capture short film' but this is for compositing live action footage and has nothing to do with the motion capture process itself.

dzonatan · **Joined:** Mon Oct 31, 2016 1:54 am **Posts:** 15

okay but what about the yellow spots?
Should I use those black out materials you provided or should I just go with regular towels?
I tried around with small towels I have and they seem to work good.
Funnily enough when I picked up a kinect and moved it closer to where those yellows spots are they simply dissapeared.

Also the wiki did mentioned that green backdrop does help out especially if you go out of your way and dress up every body part with a different primary color.

Greenlaw · **Posted:** Thu Nov 17, 2016 7:02 am

You need to read the wiki entries more carefully. Color has absolutely nothing to do with Kinect capture. Kinect only uses depth data for motion capture. It's the PS3 Eye and other RGB video cameras that use color data.

Color does affect PS3 Eye capture because that device only records RGB video data so Mocap Studio needs to be able to distinguish the color of the arms from the background environment and the torso. The actual colors are not very important, you just needs a clear contrast between the actor and background. So, if you have red sleeves, green can be ideal. If you have green sleeves, red can be ideal. If you have yellow sleeves, maybe purple will work. To be clear: This info is for PS3 Eye capture, NOT for Kinect capture.

Kinect does not need to distinguish color because it has physical 3D geometry to work with. Generally speaking, color meaningless to it. (Yes, Kinect can also record RGB data but Mocap Studio does not use it for motion capture. The RGB channel is only used for mag-light calibration, and you really only need that method when you're using three or more Kinect sensors.)

The point is, the only good reason to specifically have a green screen is if you intend to also use it for chromakey shooting. A green screen itself isn't specifically useful to iPi Motion capture and it especially doesn't do anything for Kinect based capture because Kinect doesn't use color for motion capture, it uses depth.

Greenlaw · **Posted:** Thu Nov 17, 2016 7:09 am

BTW, the yellow spots as seen in your second post are fine. These should not affect Kinect capture quality. You'll almost always see some yellow spots and the ones seen in the picture are common.

Basically, yellow spots in the area outside of the capture space do not affect the quality of capture.

Yellow means that data is unusable for reconstruction, so if it's yellow in a area you don't need, don't worry about it.

The time to get concerned about the yellow areas is when the color is present in a majority of the recording, especially in the usable capture space and on the actor.

Greenlaw · **Posted:** Thu Nov 17, 2016 7:17 am

What you want to avoid with Kinect capture is:

1. Shiny surfaces that can reflect light rays. This can mean glass, metal, plastic, polished floors. If you have any of these and your Kinect is pointing towards it, cover it up. Naturally, you want to avoid wearing shiny clothing and lots of jewelry too, especially if you use a light to calibrate. (I wear glasses most of the time but that seems okay. For calibration, I prefer the panel method to avoid light reflection problems. A 3' x 4' sheet of foam core works great!)

2. Kinect doesn't care about color but solid matte black surfaces can affect capture for the opposite reason: it tends to absord light rays. Because of this property, you generally don't want to wear matte black clothing. (Unlike PS3 Eye capture, in which case, a short sleeved black T-shirt is recommended.)

You can tell if either will present an issue when the surfaces shows up as yellow data. So if it's not yellow, don't worry too much about it. In general, this is probably more of a problem with first generation sensors and much less so for newer sensors like Kinect One.

Greenlaw · **Posted:** Thu Nov 17, 2016 7:32 am

Just for additional clarity: The yellow seen in the first post may possibly be a problem, even with the curtain. Personally, I would just wait till dark. But leave the curtain up at night because it will at least block reflections from the glass. For that matter, make sure it covers all the glass. The glass will bounce back the rays and may potentially affect the quality of the data.

If you must record in the day, I think what you have now might be okay...it's just not 'ideal' but that might not matter.

TBH, you might be overthinking this. Just record some motion and see if there are any problems tracking it. If the data doesn't work, then think about what's causing the problems and tackle the specific problems. It may turn out that the data you record is just fine.

Greenlaw · **Posted:** Thu Nov 17, 2016 8:05 am

Re: Black out material vs. towels and blanket. It really doesn't matter if you just want to block out the light.

Black out material may be more effective, and you can get it cut to size, useful if you have a large or odd-sized window. But if you have a heavy towel or blanket that effectively blocks light, sure why not?

You might also consider that black out material is lighter weight so it's probably a lot easier to hang than a heavy blanket. Just a thought.

If you plan to do this often, I guess it really comes down what will be more convenient for you.

Personally, I would probably just get black out shades and draw them down when I needed them--that seems a lot easier and less messy to me. Since you can cut the shades in width and length yourself, you can make them fit snugly in a window frame. (At least that's how they work in our computer room. Check the structure of your window and examine how the shades work at the hardware store before buying them.

My room is 3.6m x 3.6m. Is it worth trying to mocap?

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