milki
You will need a parrallel calibration between the 2D surface and the IR-Camera. Then it is simply maths to calculate velocity:
V= x/T
    V= Velocity
    x = displacement
               x pixels moved on the ir-camera = x distance on the surface
    T = Time
               time = 'IR stop detected' - 'IR start detected'

benpaddlejones

Thanks for an interesting problem to pass the time at work 

So assuming:
    -- There are more than 4 points of moving IR lights on your surface.
    -- Your surface remains in the same place relative to the wiimote, while the IR lights on the surface move.
    -- You know the size of the surface

You could find the scale by setting an array to be filled with the max and min values of the X and Y coord of the wiimotes IR location. After some runtime of the wiimote picking up random IR dots, the max and min values could be turned into to (x,y) points with which a square could be made and then compared to the size of the surface.

____For the tracking problem, I am trying something on another project that might help you._____

This is what I am trying to do.

Record a (x,y) coord of an IR point into an array. If another coord point is detected in square radius size (5-10 pixels) (within a set time, 100ms) set a flag that this is a tracked IR point.

Knowing two points you find a "guessed point" (simple delta X/Y) of where the third point will appear. If then within a set time (100 ms) and set square radius ( 5 - 10 pixels) another point appears add it to the array.

For your project you would then accumulate many arrays of points. Once an array hits a certain minimum size, take the distance traveled over the time since the array was made and you have a velocity. Take a moving average of all these velocities from all the arrays and you have your speed.

Oh, I see. I misread part of it.

For scaling, I would think you would have to know either the distance to the surface or a constant spacing between the IR dots (or some way to get back to those two variables). Even an average distance between the IR points could possibly work.


For tracking it comes down to how the Wiimote handles more than 4 points of IR light, which I don't really know.

   -- The wiimote runs at 100Hz (so if tracking IR dots thats 100 events per second right?)
   -- I think that the wiimote picks the 4 "brightest" IR points to track, then sends that data out

So my guess would be the wiimote calculates the 4 "brightest" points each cycle, so 100 times a second (that is a rather large guess).

For your application the brightness of the lights would change constantly, so each second the wiimote may send (x,y) point info for maybe 20 "true" IR points but of coarse would send the (x,y) points as locations of one of its 4 "points."

So i figured recording all the data sent by the wiimote, you could process it to get the movement of the true IR points, not the jumbled data that the wiimote may send.

This is all based on some guessing though, so it may be wrong.

There is another post on wiimoteproject about using the Hz of the LEDs to track more than 4 points, but it seemed to be ineffective.

I only have one IR point working now, but when my reflective tape arrives, I can make more and might test out the effect of many points.