VelogicFit 2D Motion Capture

Bike fitters, coaches and retail owners know Iíve been pimping a new motion capture system to them. Iím writing about it here for 2 reasons: So that your local fitter can see it in an editorial display, with graphics and whatnot; and so their current and prospective customers (you) can see what it is they might be buying, and why.

The image immediately below is from a screen display you get from VelogicFitís new 2D Real time Motion Capture system. Is this groundbreaking? Not especially. It is newsworthy only in this way: Iíve been asking somebody Ė anybody Ė to make the industry an affordable, real time, dependable, motion capture system. VelogicFit did it. It costs $1,500 which is expensive but real time motion capture used to cost almost 10x this cost, so, whatís cool is that itís within reach of bike fitters.

Bear in mind that the fit bike fitters put you on (like the bike in the videos below) will cost between $7,500 and $40,000 dollars. This software Iím writing about is an additional cost. So, if motion capture is another $9,000, or $13,000, at a certain point you see why itís kind of pricey to get a bike fit at your local shop.

The best known motion capture system in bike fit is RetŁl. ďWait!Ē you might ask. ďRetŁl isnít a tŁl, itís a system.Ē Well, it started as a tool, and a pretty darned good one. But the company felt that it needed to expand into a system in order to make money. It was (and is) a system designed around a tool, and the tool is designed around a technology, and a thesis. RetŁl's tech is an infrared camera that can tell where certain points are in space, shot with enough frames-per-second to create a record of your movement (and draw and measure angles at important points).

RetŁl is 3D. It not only knows where and how your knee moves up and down, but in and out. Thatís neat. But itís only necessary if you need to measure medial and lateral movement rather than simply up/down and for/aft. In my opinion, most fitters donít measure, donít care about, or donít know what to do with information other than whether your knee is traveling up/down or fore/aft. If the knee is moving inward or outward, yes, thatís an issue, but itís typically dealt with during an analysis of pedal/shoe interface, and often fitters will use another tool to track and measure this (a crosshair or line laser shot from the front of a riderís knee).

Therefore I asked myself a question: Is there a camera or sensor, like Microsoftís Kinect camera but not necessarily that camera, that was sensitive enough to wirelessly generate an accurate picture of the body in motion, with sufficient frames per second, with the required precision but not with extra precision that added needless expense without generating benefit? Further, is there a company that can build software to harness that capacity, and sell the whole package for a rate that would not cause the entire industry (flowing to what end user pays) more than is necessary?

Here were my imperatives:

- Must be real time: Yes, there are free or cheap systems that allow you to measure angles, but after the fact. Not real time. You draw in the angles after the file is saved. I want angles measured during the fit session, so you can make real time changes as a rider is pedaling and then see the real time result.

- I need to see the results, real time, and to have the min or max body angles noted and saved.

- I need the system to produce a video, so that the customer can see what he or she looks like while riding, and prospective customers can see what your fit sessions produce (you should see a portfolio of fits, to see if thatís the fitter you want to have set you up on your bike).

- It needs to be affordable. As in, $1,500 or thereabouts.

- It needs to be upgradeable, and it needs to be modular, to dovetail with other software products that software engineer might make (and Velogicfit makes additional, really cool, bike fit software).

- It needs to be wireless and not buggy. It needs to work in light that is not optimal, and against dodgy, busy backgrounds.

- Should be quick to set up and take down.

- It should not automatically generate and send a send a report to the client (the fitter may well have his own report format).

I took a video of the system taking a video, and that is the video above. The software itself couldnít be easier to use. Itís Windows (10) which is my one beef. Iím a Mac guy. But I have a Windows laptop because you just need one it seems like (Windows, I just canít quit you!), and besides I have my Shimano e-tube project and other such software. The Mac is my lap dog, that lives in the house. The Windows is my guard dog, who lives in the workshop.

The video below is one of several "captures" during the fit session. I'll get to this. First, let's talk about what you need to make it all function.

What you need is a Kinect 2nd-gen camera. You can get those cheap. Used, even. I get them used at Gamestop for $30. Youíll need a $40 adapter that takes the camera from Xbox to USB. VelogicFit will tell you what to get. Your computer must have some minimum requirements in the form of sufficient, RAM, and USB 3.0, and I bought a new HP laptop online for about $500 that has everything I need (my guard dog). I bought a $29 tripod. Basically, I was up and running for just over $2,000 and that included the new computer I bought just for this system, and which I also use for Shimano e-Tube project and other guard dog duties.

In the video highest above (which I took with my iPhone) youíre looking at the back of a Kinect camera. Youíll see I have a line level sitting on the camera in the video. The camera needs to be level. VelogicFit says the camera needs to be 1.7 meters from the subject. I find that distance is not really a critical element. Put the camera pretty much where you want, within reason.

How the software works: Downloading it was easy and straightforward. You click on the desktop icon and the software boots. If you look at the laptop on the lower right of the video highest above youíll see what the laptop is doing while the subject is pedaling. What you see on the laptop looks exactly like the report printed above, except you see the subject pedaling and the numbers changing as he or she pedals. But letís go in orderÖ

Velogfic ships you a bunch of adhesive reflective dots, which theyíll ship you again when you run out, or theyíll tell you what dots to get. You canít just get any dot. There is documentation that tells you where to put the dots and knowing the landmarks is necessary if you want to rely on Velogicfitís analysis of the fit (they, we, everybody has acceptable ranges for the body angles measured, just, the ranges correspond to landmarks, so, pay attention to where they tell you to put the dots). You put the dots here:

∑ Foot: 5th Metatarsal
∑ Ankle: Lateral Maleolus
∑ Knee: Distal Femoral Lateral Epicondyle
∑ Hip: Greater Trochanter
∑ Shoulder: Greater Tuberosity of the Humeral head (not on the Acromion)
∑ Elbow: Lateral Epicondyle
∑ Wrist: Centre of the Distal Radioulnar joint

The rider gets on the bike. I find I need to put the dots on after the rider is on the bike, because if the rider rotates his wrist, for example, that hides the dot from the camera. As soon as you put the dots on, the camera picks them up. If you have 6 dots, or 8, on the subject, this confuses the software and itíll tell you. Itíll show you where the problem lies (in the form of red dots in areas where it thinks it sees a dot).

For example, this rider had reflective writing on the side of her knicker tight, which the software recognized as a dot. I had to place tape over the writing, and the software was then happy.

Thereís a CAPTURE button on the screen and if you press it the camera then takes a 20 second video, recording real time the body angles. You can then make changes based on the numbers. You can record as many 20 second clips as you want, save what you want, discard the rest. The video you save is then exported in a rather smallish (3mb?) file for export to your Youtube Channel portfolio (or sent to the client along with his fit report).

In the videos above I made it about as hard as I could on the software, dimming the lighting, busying up the background, and the system still did admirably well. When you see in the video the solid green lines breaking for moments, replaced with red dots, that was the system saying, briefly, ďWhoa there! Something does not compute!Ē But the system quickly re-recognized the reflective dots and returned good data.

VelogicFit makes a 3D system as well, and the screen looks as it does in the video above. The 2D system looks pretty much the same, except the 3D system shows more fields. There is a beefed-up version of the 3D system that has the capacity to make a fairly good guess at the rider's drag. Follow the link to VelogicFit's website and you'll see the suite of products they offer.

Here is the operative question for fitters: Are the angles the body makes drivers of fit? What I mean is, is this how you make your decision? Does the riderís hip angle at top dead center, as measured by your motion capture system, determine whether the Pad Y you choose for your client is 645mm instead of 660mm? What we always ask you to consider, when you take a F.I.S.T. Bike Fit Workshop at our school, is: What drives the fit? We tell you what we think should drive the fit but in the end itís the fitter who must make that decision. So, to fitters, I ask you: Do body angles drive the fit? Or do they at least play a part in making sure the fit is appropriate? If yes, then real-time, easy-to-set-up, no-bug mocap is what you need. The system previewed here pretty much does it all. I donít feel that 3D is a critical requirement until you start to look at frontal area (and that's a separate discussion).

For those who are interested, Velogicfit is where youíll fine this product. Most of what they sell has an annual service fee, and this was another imperative of mine. You buy it, you own it. Accordingly there is a code Ė FIST2D Ė which if used absolves the buyer of the first yearís fee and every subsequent yearís fee.