Dampe had some good ideas. I would do it exactly like he suggested. Unfortunately I ain't got 4 cameras.
I would not try to work with live webcams, instead record with 4 MiniDV cameras, then import the videos over firewire and save as Avis with sound. Now each of the 4 avis has an audio channel that can be used easily to sync the 4 avis. You may use eg. the FrameGrabber I posted in the archives lately to access the frames of the avis
Using multiple colors is the easiest way to track several joints easily. Painting the pingpong balls may work too. Christmas tree lights is ok, but they are not so cheap. White LED diodes are pretty cheap and you need only about 15 of them, so maybe it's cheaper to build this yourself, at least LEDs last much longer than the minibulbs of christmas light thingies.
Using Blacklight and fluorescent colors is an option too. You may use teethpaste to make any color fluorescent.
I have also seen solutions that are using IR-Lights (used for Video cameras to film at night) and those security reflectors kids sometimes wear on their way to school etc, materials that can be found in bycicle shops too.
The tracker will have to track the root point that may be the belly. All other points are joints, their rotation is relative to their parent joints and may be calculated using Atan2 etc.
It's all pretty simple as long as you can live with a 30 Hz sampling rate. Only the 4 cameras may cost some money. There are pretty cheap cameras, not really MiniDV cameras, but some pseudo video cameras that are recording to memory disks. I think you can find a camera that is good enough for about 100$
With this equipment it may be possibe to produce pretty good MotionCapture Data. It's then only one further step to apply the Data to an animated B3D.
I would not try to work with live webcams, instead record with 4 MiniDV cameras, then import the videos over firewire and save as Avis with sound. Now each of the 4 avis has an audio channel that can be used easily to sync the 4 avis. You may use eg. the FrameGrabber I posted in the archives lately to access the frames of the avis
Using multiple colors is the easiest way to track several joints easily. Painting the pingpong balls may work too. Christmas tree lights is ok, but they are not so cheap. White LED diodes are pretty cheap and you need only about 15 of them, so maybe it's cheaper to build this yourself, at least LEDs last much longer than the minibulbs of christmas light thingies.
Using Blacklight and fluorescent colors is an option too. You may use teethpaste to make any color fluorescent.
I have also seen solutions that are using IR-Lights (used for Video cameras to film at night) and those security reflectors kids sometimes wear on their way to school etc, materials that can be found in bycicle shops too.
The tracker will have to track the root point that may be the belly. All other points are joints, their rotation is relative to their parent joints and may be calculated using Atan2 etc.
It's all pretty simple as long as you can live with a 30 Hz sampling rate. Only the 4 cameras may cost some money. There are pretty cheap cameras, not really MiniDV cameras, but some pseudo video cameras that are recording to memory disks. I think you can find a camera that is good enough for about 100$
With this equipment it may be possibe to produce pretty good MotionCapture Data. It's then only one further step to apply the Data to an animated B3D.