Camera looking down vs camera from underneath

Given the frequent use of 8 sided dice in you screen shots, I was thinking camera from the bottom using lightly smoked glass might make the extra non-relevant - yet visible - faces easier to ignore.

I was thinking camera from the bottom using lightly smoked glass might make the extra non-relevant - yet visible - faces easier to ignore.

i don't know enough about optics, but maybe someone who does could shed some light on the question of whether it's possible to create a glass "surface" (lens?) that had the effect of making something the details of an object laying flat against it very clear, but rapidly blurring anything that was even a couple of millimeters away...

to some extent, some of the privacy films you can put on glass has an effect in the same vein -- but this would have much more precise requirements..

QuoteI was thinking camera from the bottom using lightly smoked glass might make the extra non-relevant - yet visible - faces easier to ignore.i don't know enough about optics, but maybe someone who does could shed some light on the question of whether it's possible to create a glass "surface" (lens?) that had the effect of making something the details of an object laying flat against it very clear, but rapidly blurring anything that was even a couple of millimeters away...

It's been a while since I worked in optical - like over a decade... But if you have an (eyeglass) optical surfacing lab in your area. You should be able to get them to surface a custom CR39 (very high grade plastic) lens for you. The blanks are (IIRC) ~3" in diameter before they are cut down into the eyeglass frames - so there's a good bit of material to work with.

The object here is to get the (camera facing base curve as close to 0 as possible so the back side can be slightly cupped - say a 2-ish diopter curve. this will help to gently coax the die to land in the center...and push anything outside the directly contacting surfaces out of focus helping to blur/hide it. Also the use of a polaroid (sunglass lens) might make it an even better hide for the edges ... and/or just help hide the camera/look cool.

The unsurfaced CR39 lens blanks are almost an inch thick to start with, so you can pretty much pick what you want for thickness to screw into or glue onto. Actually I was thinking - Steampunk - go with the cup style roller from your video, get the edge of the lens beveled, and use an eyeglass frame style mount to put the lens in the bottom of the - lightly polished/brushed brass - cup.

Clearly I need a clever engineer to take on the hardware half of this.. Anyone up for it? With a prototype we could kickstart it

Plastic dice aren't that heavy...so as long as the dice aren't made of metal or glass, the CR39 lens/base should hold up just fine. I've worn glasses for years, and they're surprisingly hard to scratch.

yeah something like that could work, driven by a motor.
Especially if the bottom funneled the (single) die down to a smaller more predictable area. having a smaller (say 1-2 inch diameter) bottom area (think of a CUP shape or upside-down cone), it would be able to rest closer to bottom of base.

That does seem to offer a fairly reliable way of shaking up the die too.

Well there's no reason that the lens curve has to be the entire "cup".. the lens could simply be the BOTTOM of a more pronounced and sharper dimple in the bottom of the container that spins.

Think of the spinner as being formed from two of these, where the bottom of the cup is the lens, and the two cups are attached at their wider mouths.



And of course there is no reason the container has to be symmetrical.  you could have the sharp-sloped cup on one and and more of a half-sphere on the other (like an ice cream cone) -- whatever would better tumble the die.  The key thing is that when the cup end comes to rest, it constrain the die to a very narrow region on the base.  That has 2 advantages: First, it centers it above camera more narrowly, and second, it means less clearance distance needed so the bottom of the cup can be closer to camera.

A screenshot showing results of a very quick test of unsupervised clustering.

In this case the system took 17 photos and was told that it was taking a picture of a 6 sided die. It then grouped the 17 photos into 6 clusters most similar to each other.
(There was no stage of training telling it what each side of the die looks like).

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This gives you a sense of how the procedure would work for testing a die for fairness.  User would insert a die and specify how many unique faces the die has (N).  The system would then start rolling the die taking photos, eventually clustering the images into N clusters, and then computing statistics on the frequency and patterns of seeing cluster.

A screenshot showing results of a very quick test of unsupervised clustering.

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I'm embarrassed to admit that I was staring at the white circles in each of these pictures thinking each circle was a separate die, and I was rather bewildered at how I couldn't tell any of them apart!

I clearly need help with the hardware design and manufacturer.. any engineers here willing to give it a try?

Let me summarize the basic kinds of approaches we've discussed:

1. Camera on bottom looking up, with a tumbling/rolling container above. Notes: We don't know how far away the cheap raspberry pi camera will have to be to focus. We don't know how hard it will be to ignore background when facing up and looking at the sky (as opposed to looking down on a single color base).  There needs to be an easy way to insert and remove dice.
2. Camera above a container that spins to tumble (think a die bouncing on a roulette wheel).
3. Camera above a container that is "tapped" in different places from below to bounce die around.

Any other options?

To summarize the technical goals:

1. Good lighting so the camera doesn't see shadows, and has a predictable background behind dice.
2. Simple to ensure reliability with tens of thousands of die rolls.
3. Reasonably cheap/easy to build (i suppose this is least of our concerns).
4. Easy to add/remove dice.

So, the $10 dice rolling machine ordered from amazon arrived today, made in china, shipped from germany (i will never understand the economics of this stuff).

At first glance it seems to work pretty well at creating a random die roll.

Considering beaglebone instead of raspberry pi..

Though i do like the easy availability of camera and touchscreen for the raspberry pi, so i think probably that's still the best way to go.