I can easily charlieplex 64 RGB LEDs, using 16 pins (should work on any arduino). 100 would be pushing it...
Charlieplex theory and charlieplex practice are two different things.
How much wire would he need to put each LED 4m from the Arduino? What would be the diameter of the bundle of wires coming out of the Arduino (to the nearest cm)?
What would be the on/off ratio for each LED? How would that affect their brightness? How would you arrange the current-limiting resistors so that R,G and B are equally bright (assuming you actually bother to use any)?
Finally ... (and this is the biggie) ... how would you do PWM?
I've posted lots of links to the documentation, but here they are again...
Easy, is kind of subjective, but charlieplexing uses very few parts, and has less connections, so in many senses, its harder to make a mistake. It does require careful part placement, that is the key to success in charlieplexing.
Yeah, the super long wires is going to be the difficulty, but thats also true of about most methods.
Im not positive of the duty cycle, but it uses 16 microcontroller leads, and my guess is it only controls 8 LEDs at any one time.
Any-Plexing does diminish the brightness.
I have one running right now with sixteen 51 ohm resistors, it uses 2 resistors to light up 1 LED, so it has 100 ohms limiting each LED. Its not as bright as the cube with no resistors, but its still very nice, and bright enough to see during the day, but not as well as the original cube.
Color and intensity can be manipulated in software, but I havent spent much time there, and i dont have the specific answer to those questions, but you can download the software and look for it, if its worth the effort to you.
Heres the original documentation:http://aglick.com/charliecube.html
and heres some that Ive written to try to make it easier more people to make them.https://sites.google.com/site/rgbledcubes/home/charliecube64
I still have a lot of work, so some bits may need clarification, and re-writing, but hopefully its good enough.
This is sort of like what I was thinking about when I mentioned serial LEDs. https://www.adafruit.com/products/322
Im not saying you should use their product, or that size LED, but rather that method of controlling the LEDs.