Under-lit translucent dance floor w/o shadows

I know this is mildly off topic, but I love the raw brain power around the Arduino forum, so any input would be appreciated!

I am planning on making a huge 8’x8’ wide and about 1’ tall platform with oh, around 625 individually addressable LEDs (in a 25x25 grid) underneath. Each LED is coupled, and I understand this is overkill, with an IR transmitter / detector to detect with good accuracy where people are standing and at what distance from the platform.

I’ve been doing a good chunk of research, and I think I have most of the electronics side licked (thanks Due! 1 million ADC samples a second! Woowee!), the general flow I’m planning is going to be IR > Holy Mux Town! > Arduino > Raspberry PI > Arduino > LEDs. Like I said, most of this I have figured out, although any examples of people multifudging 625 phototransistors would be helpful (I should probably take it as a clue that I can’t find any examples ^_^).

The part that I’m completely out of my element on, and I hope y’all have some insight on, is the structure itself. I’m really picky about the aesthetics, and I would love it to be made of frosted acrylic and lit from the bottom. I’ve seen examples of a webcam / projector approach, but I doesn’t really accomplish the look/reactivity that I want. So, that being said, I know I need support underneath for a 8’x8’ (will probably be 4 - 4’x4’ sheets) sheet of acrylic, but the only supports I see would cast shadows from the LEDs, and the above surface won’t look it’s completely evenly lit. I’ve only seen a few examples of someone doing this, and the few I’ve seen typically accomplish this by segmenting the platform into a grid, making it kinda a pixelated thing which isn’t really the look I want.

So, I ask the collective genius of this forum if y’all have any ideas of supporting (btw, how much support do I need? Can’t find any good equations on that) the platform without casting shadows. I’ve thought maybe some acrylic rods, but they will refract, although maybe with enough diffusion, it’s a non-issue. Also, how thick does it need to be? I’m guessing 1/2" should be good with enough supports, I understand the thickness and the amount of supports are inversely correlated. Anywho, I’m having a hard time even thinking about how to approach the problem.

Well guys, thanks so much y’all, I rarely post to forums but I feel like I have looked everywhere.

Just lay it all out then fill it with something like lucite?....clear, hardening resin? Then can install floor covering over that.

It won't be very portable, and will weigh a ton....but would solve your shadow & support issues.

You could, I suppose, also use a similar method to produce 4 x 4 (or 8 x 8, whatever) "tiles" which could then plug into eachother. This would keep it more portable and, at least" moveable from one location to another...? With an air gap, or diffusion layer between "light bricks" and visible floor covering, any pixel or tile looking effects should be minimalized.

Good luck!

Post photos if/when start making progress! :)