Dice Rolling Machine
Lucky Dice Roller Cup Set with 5 Dices (battery not included). Push-button automatic rolling. Built on a black cover on the transparent cap ensures that your dices are not seen by the opponents. Dimension: 10.6(diameter of base) x H11.4cm Dice Roller is powered by 2 x AA batteries(not included). Chaotic systems, like rolling dice, are almost impossible to control. For example, the well-known amusement park ride, the Tilt-a-Whirl is so chaotic that the gravitational influence of a person randomly walking around within a hundred feet of the machine will make the angular position of the cars diverge within a minute or two.
May thy dice chip and shatter | Other News |
Introducing the Dice-O-Matic mark II, now generating the die rolls on GamesByEmail.com. It is a 7 foot tall, 104 pound, dice-eating monster, capable of generating 1.3 million rolls a day.
Currently, GamesByEmail.com uses some 80,000+ die rolls for play in games like Backgammon, Gambit (a RISK clone), W.W.II (an Axis & Allies clone) and others. To generate the die rolls, I have used Math.random, Random.org and other sources, but have always received numerous complaints that the dice are not random enough. Some players have put more effort into statistical analysis of the rolls than they put into their doctoral dissertation.
A few years ago I tinkered with a dice rolling machine made from Legos. Though great fun, it was noisy and cantankerous and unreliable, and it never recovered from the move two years ago. But it had made players happy, at least for a while. So I decided to make a 'professional' grade rolling machine.
I had been slowly accumulating parts for over a year when I put out a plea for financial assistance. Many players donated small amounts, and a few made some over-the-top donations. I also received a large donation of the elevator parts. The help allowed me to gather the last and most expensive bits, and four months of spare time later, everything is working better than planned.
I had a soft target of a machine capable of 200,000 rolls a day, as site traffic is growing. However, any automation project worth doing is worth over doing, and I way overshot the mark. The result is what you see here: a machine that can belch a continuous river of dice down a spiraling ramp, then elevate, photograph, process and upload almost a million and a half rolls to the server a day. I may not get nominated for a Nobel prize, but the deep rumbling vibration you feel more than hear when two rooms away is quite impressive.
Dice Rolling Machine Online
There is no doubt that I will still receive complaints about the rolls, but now I can honestly say I have done all that I can possibly do: the rolls you get are exactly as random as those you would get throwing by hand. As I promised earlier, if you donate to the site and are unhappy about the rolls, let me know and I will pull a die out of the machine, melt it flat and mail it to you, as an object lesson to the other dice. Tangible revenge.
Details of the Dice-O-Matic
The Dice-O-Matic is 7 feet tall, 18 inches wide and 18 inches deep. It has an aluminum frame covered with Plexiglas panels. A 6x4 inch square Plexiglas tube runs vertically up the middle almost the entire height. Inside this tube a bucket elevator carries dice from a hopper at the bottom, past a camera, and tosses them onto a ramp at the top. The ramp spirals down between the tube and the outer walls. The camera and synchronizing disk are near the top, the computer, relay board, elevator motor and power supplies are at the bottom.
The dice start the cycle at the top of the ramp, toward the rear of the machine. The ramp is comprised of ten steps, each at about a 20 degree incline, with a right hand thread through two and a half spirals. Two layers of cloth covered foam (car headliner) keep the noise down. Felt covered foam quarter-obelisks are at each corner, sewn to the side padding. It took a few tries to get the pitch just right. Too shallow and the dice stopped tumbling, too steep and they would start banging against the Plexiglas. Now they roll very well, sometimes stopping and then getting knocked back into the stream. Perfect.
The hopper at the bottom of the ramp is pure seething violence. I am sure there is a better way to load the dice into the buckets (vibrating tables and all that) but not in the budget and footprint I have. Instead, buckets come up through the bottom of the hopper, smashing their way through the accumulated pile of dice and scooping some up. It is rather hard on the dice, much of the paint gets chipped from the edges of the pips. The buckets are close enough together that dice cannot slip through the bottom.
The 'buckets' are lengths of 1/2 inch aluminum U channel, about 5 inches long, attached to chains on each side. I cut grooves into each side of each leading edge, then slit and mounted plastic stir straws to reduce the noise and impact levels. Up to six dice can fit on a bucket, and tend to ride at a neat 45 degree angle.
The chains and attachment links are the key to the whole machine. The chains are ANSI-35 with A-1 attachment links every tenth link. I had a number of false starts with cheaper ladder chains and homemade attachments, but they simply were not up to the strain, always stretching and rattling apart. After getting the professional grade hardware, the design changed so much for the better. The hopper, buckets, and camera became a simple, streamlined sequence all from using the proper chain.
The two chains ride over 20-tooth drive sprockets at the top and bottom, powered by a car power window motor on the bottom shaft. The motor and sprocket shaft are coupled using a short piece of vinyl tube and some hose clamps. This gives some leeway in the motor-shaft alignment and provides a simple slip clutch in case something jams.
The buckets rise pretty fast, traveling over a foot per second. It takes about 5 seconds to go from the hopper to the camera near the top. Along the way there are plastic flaps to beat against the dice and make sure they have settled properly into the buckets.
Had you told me two months ago that getting the dice settled into the buckets would be the trickiest part, I would have called you insane. Processing the picture, probably. Getting them reliably into the buckets to begin with, maybe. But getting them settled once they are in, when they have tendency to settle properly anyway? What is the big deal? The deal is that some orientations you would not believe even possible, much less stable, turn out to be ridiculously frequent. A die will happily rise out of the combat-fury that is the hopper, land on an edge, and ride on that edge all the way up five feet of vibrating chain. I have seemingly impossible pictures of dice posing quite daintily on their corners, thwarting the camera by not showing a face. It certainly helped me appreciate the fine art that is automated orientation.
A machine vision/inspection camera is near the top of the elevator, looking down at a 45 degree angle to match the dice in the buckets. 20 bright white LEDs surround the lens so that the exposure time (1/2000th of a second) is short enough to eliminate any blurring.
The synchronizing of the exposures is accomplished using the camera's external trigger connection. As mentioned, the buckets are 10 links apart and the sprockets have 20 teeth, so two pictures are needed for each rotation of the shaft. A disc with two slots 180 degrees apart rotates between an infra-red LED transmitter/receiver pair on a home-built circuit, and the pulse triggers a snapshot.
After the picture is taken, the buckets crest over the top sprockets, which throws the dice out onto the ramp. In all, it takes about 13 seconds for an individual die to make a round trip. There are 200 dice in the machine, each rolling four times a minute, totaling over 1,330,000 rolls a day.
The dice are not true 'Michigan Red Eyes' as I had earlier thought, but have different colored pips for each value. The different colors make it pretty easy to count rolls. For example, if 6 yellow dots are found in the image, there were three 2s rolled, no need to worry about determining the proper grouping or orientation of pips.
The images captured by the USB camera are processed by software I wrote in .NET. The camera comes with a nice software development kit with a ton of features, and you can fine tune every aspect. Because the computer cannot quite keep up with the elevator at full image resolution, the images are sampled every 3rd pixel horizontally and vertically.
The image processing begins by looking for the bright white of the dice. This eliminates everything except the faces toward the camera, and these are the areas of interest. Inside those areas are holes of darkness. The size of the hole determines whether it was a pip or not, and how many pips it represents (sometimes the pips of 6s bleed together). The average color of the pip determines the value it represents. The pips are then counted left to right and rolls the determined. The data is uploaded to the server via wi-fi in blocks of 1,000 rolls.
The program also controls the power to the lights, camera trigger and conveyor motor using a slick little USB relay board. When the server has enough rolls in the bank to last for a few weeks (I am currently storing a million or so), the conveyor shuts down until needed again. It runs for maybe 1.5 hours total each day.
The new D&D set includes cards that have players roll 20-sided dice. The only 20-sided dice that Magic players frequently carry with them are spindown dice, where the numbers count up sequentially on adjacent sides. (Although notably the dice for this prerelease in particular are not spindowns.) So the age-old debate around whether it's ok to roll those for a random result has finally become relevant to Magic. There are four angles from which I've seen people claim this is a problem, which I'll go though one at a time.
'Spindowns aren't designed for rolling, so their manufacturing process doesn't try to make them fair.'
This does not seem to be true. Most dice designed for casual gaming use a pretty lazy manufacturing process and aren't completely fair. (The dice being marketed in that video aren't much better.) You'll notice if you look at casino dice that they don't have physical holes in the sides that could lead to weighting differences, don't have rounded edges that reduce bouncing, aren't made out of multiple colors of plastic that could be different densities, and are transparent to ensure that there are no air bubbles. The dice you buy in your LGS aren't like that, and they're already slightly unfair even if they're not spindowns.
'All the high numbers are at one end and all the low numbers are at the other, so any accidental imperfections are more likely to result in a consistent bias towards one end of the scale.'
This is true, but there are some mitigating factors.
The first is that any bias in the results is very small; just fractions of a percent. While in theory this is still a problem, in practice it's significantly less impactful than the biases you get from improper shuffling, which is far more common.
Secondly, this bias is going to be random for each die. One die might be more likely to land on high numbers, and one die might be more likely to land on low numbers. As long as you're just picking a random die and using it, these biases will cancel out and you won't be at any advantage or disadvantage. The only way this is problematic is if a player is rolling a die thousands of times to determine what it's biased towards, and then choosing to use dice that are biased towards a specific number.
'Players can cheat by melting it.'
This seems to be mostly an urban legend. Plenty of people online claim that putting a die in the microwave oven or normal oven will affect its center of balance, but those who actually try it seem to meet with limited success. It'll likely depend on the type of die, since different kinds of plastic have different melting profiles. If someone did manage to use this method to make a die that's both significantly weighted while still looking indistinguishable from a regular one I wouldn't be that surprised, but I don't think it'll be trivial to get it right.
This is largely irrelevant, because people can just buy loaded or trick dice online. The distribution of numbers on a spindown will make a loaded one a bit more consistent, but you can't really trust non-spindown D20s either.
Rolling Dice Slot Machine
'Players can cheat more easily by rolling it in a specific way.'
'Trick shots' with dice where they roll in a predetermined way are possible, and spindowns make them easier since you only need to end in a specific region rather than one exact face. This can be mitigated by making sure that the die bounces around enough that enough chaos is introduced and the thrower can't control for a certain outcome. Casinos do this with a pointy backboard that the dice have to bounce off of in order for the roll to be valid. As long as a spindown is not thrown from a specific orientation and rolls/bounces a significant distance on the table, they're not going to succeed in achieving a non-random result.
Here is an example of me rolling a spindown in an advantageous manner. And here's someone else doing it a bit better. Could this fool someone who isn't paying attention? Definitely. But anyone doing this consistently with different people is going to get noticed pretty fast, and it'll to be nearly impossible to argue that they didn't know what they were doing.
Testing
Gamers are very prone to superstitions around dice (and to a lesser extent, randomness in general), and will sometimes roll a die many times in order to see if it's fair. Unfortunately even a few hundred rolls is generally insufficient to find small biases; some numbers will come up more often than others in any finite sample. (Here's an example of someone erroneously concluding that spindowns are actually more fair because they did far too few tests; their results were effectively just random noise.) Floating a die in salt water is another test people do, which is good at detecting density imbalances, but useless for anything else like shape asymmetries.
In order to really tell if a die is fair, it needs to be rolled several thousand or more times, like with an automated dice-rolling machine. That said, some amount of useful data can be gotten with a smaller number of trials, as described here. Keep in mind that most imperfections are per die, not per manufacturing run or per company, so just because one die from a box is fair or seems to have a bias doesn't mean the others will be the same.
(Testing a bunch of dice, finding one that rolls higher numbers more often, and choosing to use that one is obviously cheating, regardless of whether it's a spindown or not.)
Conclusion
Non-malicious differences between spindowns and regular D20s are irrelevant; if you're confident no one is cheating, there's effectively no difference. It is easier to cheat with spindowns, either by rolling them in a careful way or using one that's more likely to roll higher. The first cheat is somewhat easy to catch, but could fool a decent number of players. The second cheat takes a fair amount of effort to set up and can be done with regular D20s almost as easily.
It is in general better to use systems that make cheating harder. However, regular D20s are less accessible for most Magic players, and I'm not sure if forcing everyone to go and buy non-spindown dice is worth it just to offset such low-value potential cheats. If you're really concerned about cheating you shouldn't be using dice at all; use something like this instead. (Most phone apps like MTG Familiar also have a dice roller.) I'd encourage people to default to non-spindowns when they have one on hand, but personally I wouldn't have any problem with someone rolling a spindown die in my games for now.
Do note that in sanctioned tournaments, spindown dice are prohibited by the Magic Tournament Rules. With regards to casual play, I'd like to to quote an 8 year old Reddit post:
Friends, do everything in your power to avoid playing with anyone that has a passionate opinion about whether or not to roll a spindown die in your fantasy card game. Your life will be so much more enjoyable if you don't seek out conflict over something this trivial.