Notices by James Brown (ancientjames@mastodon.social)

There’s now an accelerometer in the base, synced to the rotation of the screen. I’m hoping this will help me get it balanced better. I don’t entirely understand the shape it’s producing, but the line is pointing in roughly the direction I think it should be pointing.

New dome!
There are many advantages to moving to smaller panels in the new design (momentum etc), but the price drop going to a 300mm dome from 400mm would be justification enough.

So many complaints about the framerate on that last video, so I decided to upload one with a shorter exposure and more flicker. But I still ended up keeping it below 30 fps, so I suspect the complaints will be about both framerate and flicker. Just have to hope the algorithm doesn’t go so large on this one. https://youtu.be/gBfclb9hXCI

In motion https://youtu.be/na7pvihXhYs

Easier to see the 3D when it's only the camera that's moving.

Now thinking I should have filmed the tool I made to press all the clips on this IEC socket so I could get it out of the housing in order to film the satisfying click it makes when it goes in.

Taking it all apart so I can film myself making it.

25 fps. That's an actual frame rate.

Enbubbled.

With the previous dome the cut had a somewhat hand made look to it, so I printed a thin piece of trim to slip over the edge and keep it neat. It was too big for the printer so I used TPU, printing it in a spiral and flexing it back in to the right diameter. An unexpected benefit was that it was way quieter with that isolating the dome from the base.
This time the cut went better, but I’m still going to give it a gasket for that reason.

There’s a fair bit of planning involved in finding the true centre and height of these domes. When I come to make the cut it feels like cleaving the Cullinan diamond.

Original voxels

2D video of 3D projection of 4D object.

This display works by spinning a matrix display rapidly about a vertical axis, lighting up each LED as it passes through part of a 3D image. The way you update the displays has a big impact on the quality of the image.
In this gif, each dot represents a column of LEDs - we're looking at the device from above. Here the panel is treated like a 2D display which just happens to be moving. Each scan line is repeatedly visited in turn, sweeping out a set of slices where the image can be displayed.

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

I do like an ample window and natural light, but it makes it hard to see the leds. Hence this pirate astronaut.

First test of the new design, and already I’m happy. Quiet, high refresh rate, and doesn’t feel like it’s seconds away from embedding itself in my face.

In practice it's complicated by the fact that these panels update two lines at once. Every time you update a column in the outer half, you're also updating one in the inner half. I couldn't find a simple procedural update strategy to spread these evenly, so I ended up generating a lookup table for it using simulated annealing.

The real improvement comes when you adjust the update rate for each column to match the length of the track they have to sweep out. Instead of wrapping around when you reach the last column, you wrap around when your counter reaches the square of the number of columns, and you update the column corresponding to the integer square root of the counter. This gets rid of the bright dense region in the middle, and adds more updates out at the edges making them less sparse.

If you turn the panels 90 degrees so their scan lines are now columns, you can do a bit better. The update doesn't have to be sequential - instead of stepping one column at a time, you can skip a few each time. As long as you pick a number which is coprime with the number of columns, and you wrap around once you go past the last one, you'll still visit each of them but spread out more evenly throughout the volume.