James BrownWell I got a lens out of it in the end. It does make it more directional, but there’s more light off axis than I need.
I went back to the slats, and finally got all the bits hooked up together.
It sort of works?
You can see what's going on a bit more clearly with a simpler shape. It looks better when you can use both eyes on it!
The depth is smeared more than I want because the collimators are too shallow (because I don't like prints that take more than 16 hours to complete). I want to make them tighter, and spin the whole thing faster to compensate.
The nice thing about these LED panels is that they're very high framerate (and cheap!). I'm updating these at 1.5 KHz - with 3 of them in a ring, that's 4.5 KHz. Just driven in software from a (somewhat dizzy) Raspberry Pi.
Just realised that I can increase the resolution by progressively offsetting each panel by 1/3 the LED pitch.
Making parts for this has been a real saga, so while I wait for a faster printer to arrive I tried removing the collimators and running it as a swept volume display. Now I’m thinking maybe that’s what I should have built in the first place.
The thing I've been trying to make creates its 3D effect by displaying a whole different view in every direction, which means it can handle occlusion and fancy lighting at the cost of vertical parallax.
To turn that setup into a swept volume (where it's lighting up the LEDs according to where they are in space - full 3D, but glowy and transparent) I keep everything but the collimators, and just render each view with the near & far clip planes set really close together.
I'll probably make two displays now - finish off the autostereoscopic one, but then rearrange the geometry so that I can sweep through more than just a thickish-walled cylinder.
A quirk of these LED matrix panels is that they simultaneously update two rows at once, separated by half the panel. So on a 64x64 panel, you update rows 0 & 32, 1 & 33, 2 & 34 etc.
However, if you want to sweep one around an axis, you ideally want to update the outer LEDs at a faster rate than the inner ones, and this layout prevents that.
However, if you want to sweep one around an axis, you ideally want to update the outer LEDs at a faster rate than the inner ones, and this layout prevents that.
I’ve mentally moved on from this design, but I went ahead and built it to the point I can call it finished.
The advantages of this approach - occlusion and view-dependent lighting - are undermined by the fact that too much of the colour depth is sacrificed to hitting the necessary framerate. The sort of simple scenes it can display could be displayed better by a swept volume.
Most of the time we don't move our heads up and down very much, so the lack of vertical parallax seemed like it wouldn't be a big limitation. But one of the situations where we do move our heads quite a lot is when presented with a neat little 3D effect sitting on a desk.
Anyway, the new display is going to be amazing.
Scouring Aliexpress for LED panels for the new display, and it seems the higher resolution ones tend to be flexible. I spent a while investigating developable surfaces* to see how I could take advantage of this, but couldn't come up with a layout that offers any advantages over a flat square centred on the axis. Seems disappointingly pedestrian.
(*Twisting a sheet of paper in my hands)
I'm arranging it as two rectangular panels arranged with their bottom edges touching on the axis, which lets me update columns at the same radius simultaneously. The outer columns need to be updated more frequently than the inner columns, and one of the nice things about these LED panels is that you choose your own update strategy - you're not stuck with scanning a whole frame each time.
If the lines were completely independent, you could evenly scan a sector with half the number of line updates compared to updating the whole frame. As it is, each line has to be updated in parallel with one that's half a panel further down, so it ends up taking 3/4 of the line updates instead (because some updates have to update the outer line while scanning out black to the inner line).
The thing about voxels is that even when they’re not working, they look cool.
New display, new panels. I'm driving these ones using DPI on a Raspberry Pi, which is a handy way of wiggling 24 GPIO lines with precise timing and no CPU involvement.
The results I was getting with the new display were so much better than the original that I went back for another pass at it. Turns out there were a couple of stupid bugs limiting the refresh rate. The colour depth is now vastly improved.
This is still using software bit banging. I'm going to switch it to using DPI, but the current interface board wasn't designed with that in mind, and the GPIO mapping doesn't put all 3 displays on valid DPI pins.
If you squizz your eyes at this, you can see the 3D.
If you have difficulty converging it, it helps to make the image really small and gradually enlarge it once your eyes have locked on.
I had the opportunity to give some live demos of this thing recently. It went over well, but the noise was a real killer.
I've reworked it to use a belt drive instead of the horrible 3D printed gear - before, it screamed; now it whirrs.
I've reworked it to use a belt drive instead of the horrible 3D printed gear - before, it screamed; now it whirrs.
I massively overestimated how much lead would be needed to counterbalance the small amount of slightly off-axis electronics.
It would be convenient to address the voxel data as a stack of horizontal slices, because that's how it's exported from lots of existing tools. I have to rotate it 90 degrees though, because scanning out is faster if each column's data can be addressed as consecutive bytes.
It's a small change, but there's a 6.5x difference in speed between the two orientations, which directly translates into voxel density in the final output.
It's a small change, but there's a 6.5x difference in speed between the two orientations, which directly translates into voxel density in the final output.
Trademark flickery mess
I really need to get a hobby where missing my framerate target doesn't make me physically nauseous.
Help me Obi-Wan Clownobi
I've implemented parts of a content pipeline for rendering a scene on the PC and streaming it to this display, but writing video streaming code is so much less fun than playing with voxels that it may take a while to finish.
Here, I've stored the animation uncompressed on the display itself, and am updating it as fast as the Pi's SD card can handle. (Not very fast.)
Here, I've stored the animation uncompressed on the display itself, and am updating it as fast as the Pi's SD card can handle. (Not very fast.)
My target for this display is 600 rpm - lower than that and it's too flickery; higher than that and I can't refresh fast enough to get 400 voxels around the circumference without dropping to 1 bpc. I'm nudging 400 rpm here, and it's still pretty unfilmable and absolutely terrifying to be close to. I have to decide whether the overall approach is worthwhile enough to start spending money on aluminium and polycarbonate.
Slightly higher rpm, slightly longer shutter.
The other problem I have is that to sell the 3D effect I need to move the camera around a lot, so I'm going to have to put some effort into building a studio backdrop.
Incidentally, those models are from Cheello's voxel Doom: https://www.moddb.com/mods/doom-voxel-project/addons/voxel-doom - It's a lovely mod, and makes Doom feel more like my memories of playing it than the real thing does.
Latest flickery mess
I had a panel left over, and I thought I should have another stab at an oscillating display. I wanted to give it an undulating motion and came up with what seemed like a nice linkage, but the end result looks like it was designed by Trevithick.
It's a nice fluid motion on the panel, but overall it doesn't bring me joy.
There must be at least 6D here.
I rewired the back of the panel to tidy up all the loose flappy cables. It now manages 600 rpm, which is not too flickery.
In the continuing quest for higher rpm, I've moved the controller down below the screen and across the axis of rotation. It's a lot harder to get at if I need to rewire anything, but it does improve the balance.
It feels as though I'm endlessly rebuilding it, for diminishing improvements. But in the most recent rebuild I finally solved a mystery that has been bugging me. When the display had been running for a while, it would quite abruptly lose balance and start vibrating. After the last occurrence, it was never quite the same. On stripping it down I found this.
That's the mount for the slip ring. A cylinder carrying a couple of copper bands fits over the pillar, and an M4 bolt goes own the middle to hold it all together. It has very clearly become bent, and without any signs of cracking. Presumably, as it spins, it heats up enough to soften the PLA, and the spring loaded brushes push it out of alignment.
I've reprinted it in ABS; going to see how well that lasts.
I continue to fail to shoot footage of it that does it justice.
This feels like a good match of style and content.
I’m now suspicious of all the PLA parts. The little pit with the Pi in it is getting very warm.
kind of feels like it needs monsters?
I do like an ample window and natural light, but it makes it hard to see the leds. Hence this pirate astronaut.
Doom running at a larger scale. Easier to make out what's going on, harder to see what's shooting at you.
https://youtu.be/bRe1OSkeiQg
https://youtu.be/bRe1OSkeiQg
Voxel Doom
hikaricai@ancientjames I am also making a kind of voxel display, but it is the mirror that is rotating, not the led screen. Detail: https://mastodon.social/@hikaricai/112274863270477644
@hikaricai @ancientjames oh, nice! Do you have any more pictures?
@ancientjames some detail is on https://hackaday.io/project/194714-volumetric-display-using-rotating-mirror. I do not have a 3d printer so currently this mirror based voxel display is made by hand, with three p2 64x64 led displays. And of course the view angle is so limited that I can only view from the top. Later I am going to transplant nds emulator to paly real 3d game.
Jochem@ancientjames delta T of 11 degrees doesn't sound as "very". Is there a fan to suck away the hot air?
By the way, love the project!
By the way, love the project!
@JHBonarius That's not where the Pi is - I just liked the picture.
Simon Frankau@ancientjames A picture of a sphere of material with "the pit is getting very warm" had me double take for a moment. DIY Los Alamos vibes.
Greg Bell@ancientjames pretty good pic for an album cover tho
Cqoicebordel ❎@ancientjames
I wonder if adding weight to the rotating part would help :
- Using metal, it would dissipate heat more easily.
- Would help the stability, if the weight are movable.
- Would stabilize the rotating speed : it would be harder to start and stop, true, but it will avoid small variations at full speed.
I wonder if adding weight to the rotating part would help :
- Using metal, it would dissipate heat more easily.
- Would help the stability, if the weight are movable.
- Would stabilize the rotating speed : it would be harder to start and stop, true, but it will avoid small variations at full speed.
sky-guided@ancientjames it looks so smooth!!
Eri@ancientjames is it loud? This is the coolest physical object I’ve seen all year.
@slink It's not quiet.
Beans (Baked)@ancientjames wooow that's cool
Queen Calyo Delphi@ancientjames Oh I hecking LOVE THIS 🤩
jonny (good kind)
Exellent@ancientjames ist there any GitHub repo or something like that. To replicate what you did? that's amazing!!! 🤩
Naate@ancientjames watching this come together and evolve is incredible! Fantastic work
vxo@ancientjames oh my gosh this is BEAUTIFUL! I've seen some kids' toys that use this same sort of display tech, but it's always like 12px high. Your high res version is amazing!
Liera 
@ancientjames damn that looks absolutely incredible! 
Instant Arcade@ancientjames is that Thunderbird 2?
@InstantArcade Dream Chaser!
@ancientjames Any chance you would shoot some 3d video maybe? Latest iPhone can do a decent job of it, assuming some Android photos can do so as well. 😄
adingbatponder@ancientjames wonky.. right... can someone explain WHAT IS THIS totally cool thing ? first I hear of it... does it have a name... ?
Violet MadderWhaaaaaaat
L'égrégore André ꕭꕬ@ancientjames Sorry for the fav spamming, but saw this in the public feed and had to check the whole thread!
Meme Poster@ancientjames Thats so fucking cool
sam@ancientjames that looks really superb.
@ancientjames
Are the scanning effects an artifact from the phone camera or does it really look like that? Because this glitch box has won my heart, its beautiful
Are the scanning effects an artifact from the phone camera or does it really look like that? Because this glitch box has won my heart, its beautiful
@jonny Mostly the camera. That was a particularly long exposure, because it was running at low(ish) rpm. Part of the drive to spin it faster is to make it filmable.
Graham Sutherland / Polynomial@ancientjames wow that sphere looks incredible
Marcus Müller@gsuberland @ancientjames that sphere looks very credible. You should listen to the voice in it that tells you how much power you can gain by following the words and will of the dark lord..
#palantirvibes
#palantirvibes
@funkylab @ancientjames with that base I keep expecting to see Sauron's Eye
@gsuberland @funkylab Oh I need to do that
@ancientjames @funkylab cannot wait :D
@gsuberland I'm so happy with how it turned out!
Keir Rice ⬢
Voxatron 0.3 Release Trailer
jeffluszcz@ancientjames What's it look like in the dark?
@jeffluszcz I'll find out in about 3 hours.
alphabetter@ancientjames the paint shop has a machine like that for shaking the cans!
Aaron Leavitt@ancientjames That could make some interesting long exposure shots.