MAKE a VOLUMETRIC PROJECTOR from JUNK

Step 4 How the FIRST one worked...

This one was made a long time ago with a MC68705P3S, which is vaguely like a PIC16C57, having about 1K.
Using dot matrix displays like these for 3D is not very impressive,
at least at the time, LEDs were not as bright, the image was very dim and could only be seen in dark rooms.
The chip was programmed with clever patterns that made layers of a rotating cube,
with 3 image phases (the cube rotated by cycling through 3 images).
The patterns were selected so that the dot matrix display would not be scanned,
but remain on as the rotor passed through the cube image.

All of the Cube volumetric projectors use unscanned LEDs to give maximum brightness.

Rotor? This was simply a chip and a battery and a dot matrix display on a computer fan.

The 3 bitmapped images each consisted of several layers of carefully designed 7x10 bitmaps (only 17 bit, not 70 bit).
Certainly they can fit in an old PIC chip.

There was an animation sequence. The cube image rotated clockwise,
then it rotated counter clockwise, then it stopped. The sequencing of the 3 images
in the animation was something like....
1231231231231231231231231 (turn one way)
3213213213213213213213213 (turn the other way)
3333333333333333333333333 (stop turning, then repeat this whole sequence)

(There is a "nut in a cube" animation on the website WMV video that plays similarly, also having only 3 frames.)

As the fan turned, the circuit was cued by a rare earth magnet passing a tape head, to dump a frame into the LEDs.

This device is very easy to make but not very impressive and if you try to touch the image it will hurt.