Old fart's comments, experiences and insights

[Greg]

Then came the later part of Echoes, that we used during Laserium I and some visual effects started hitting musical queues, so I wondered whether A.I. had tapped into an old Laserium video for its imaging synthesis.

I found Echoes on a Laserium I tape. It appears to have been edited out of the show, but left on the reel at the end. The data doesn't do much, just brings up the four channels, centered, which slowly grow in size. All channels are variable cycloid for most of it but then switch to invert spirals for the ending passages. Remember anything about what was done for imagery?

[laserist]

Echos was mostly joystick and a cycloid development number. it was edited. It started about 15 minutes into the original version with stars, the "radar" beeps revealed points with high speed CM2 for a second - so they looked white "stars" or explosions in random positions via joystick. You start with a two oscillator cycloid and joystick. A second image comes in. You add a third oscillator, and play the cycloid and joystick. You might use chopper. The end with the spirals was superimposed on the burn that started the show. As if to say - that's all folks. Fade to black. Bring up the blue lights as if that's the end of the show and Hoedown begins...

[lasermaster1977]

This has to be the worst Echoes visuals EVER.
It proves that A.I. has neither visual talent, emotions, nor soul.

At 1st, I concluded that there was no connection between the visual chaos and Echoes, just A.I. generated imagery, with the sound track added afterwards.
Then came the later part of Echoes, that we used during Laserium I and some visual effects started hitting musical queues, so I wondered whether A.I. had tapped into an old Laserium video for its imaging synthesis. Then, it started creating clones of Floyd's band members and becoming less chaotic.
Reckon A.I. needs a few thousand more rehearsals, before pretending to replace any laserists.
No worries.

It appears there are many who are quite enamored by this AI "Echo'ed" visual assault, based on the comments on YT.

I'll just add that for me: Less is more.

[Greg]

Not sure if this is at all close to what is being described. I find it not easy to settle the CYGN-A into stable harmonics.
https://www.youtube.com/watch?v=nBxwE7v_CXE

[laserist]

CYGN-A didn't do stable harmonics. Not even after they made aluminum adapters to allow a conductive plastic fine frequency pot to be mounted to the dual 1 mOhm pots. I would generally start with spinning loops - they look good with joystick. There were three kinds of laserist. One type tried to do the show exactly the way they were taught. Another type found new ways to do things over time. And the third type just sucked. Usually that third type didn't last too long...

[laserist]

Greg's image isn't colormod. It's just got a ton of chopper & a fixed rotation that wasn't available on the Mark IV that was designed for Laserium I. I don't remember exactly when the 0, 90, 180, 270 rotation was added, but it wasn't part of the Mark 6A either.

[lasermaster1977]

Not sure if this is at all close to what is being described. I find it not easy to settle the CYGN-A into stable harmonics.

Greg, that looked awesomely good in and of itself. I loved the chopper effect where one end tapers down to black.

[laserist]

The slotted can chopper could absolutely produce a vignetted chop... It's just optics, you could even adjust the vignetted chop by adjusting the width of the slot...

[lasermaster1977]

Perhaps, but in the real world, that's neither a feasible solution nor possible to modify from song to song during a show.
Furthermore, the GS 3xx (320?) chopper can's inertia wouldn't allow it to 'vignette' @ ~1kHz, which is ballpark to the spinner frequencies being used for this effect.
I'm suggesting more modern techniques, which are playable in real time for the benefit of others, who are using similar hardware and software, Brian.

Am I correct about the double chop being used for the Echoes cycloid?

Roj

I had a post "In the old days we did this" that shows my home grown PWM chopper blade that could produce exactly the tappered chop effect that Greg did.

[lasermaster1977]

Mounted onto a DC motor's shaft for variable speed, perhaps? I thought about that, but never actually tried it. My 1st was a 5mm dia. aluminum tube, mounted onto the shaft of a GS124. But, it sucked, due to internal reflections inside the tube.
I can see that the pulse width of the chop can be varied, depending upon how far the 'saw' blade is inserted into the beam path. But, in/out of the beam path @ 1kHz? What were you using to move it in/out of the beam path?
Not that I would ever doubt your words, of course.
🙄
Yo, Greg! What's the frequency of your zig-zags?

"Mounted" is the engineering term, I just HOT GLUED the cardboard chopper disc to the end of a DC motor shaft that happen to have a small, .25" diameter brass pulley pressed flush on the end of the motor shaft. The carboard was from the back of a yellow legal pad if I remember correctly. The 1" diameter 12v DC motor was mounted on one end of a .0625" thick strip of aluminum about 1" wide and a few inched long, with a "U" notch at the end for the pulley/shaft to huddle within. The motor mounting screws where through the strip on either side of the "U" notch. The other end of the rectangular strip mounted with 4/40 sheet metal screws on the end of 1" x 1" x 2" block of white Teflon. The Teflon block had about a 3/16" hole drilled and tapped through it perpendicular to the motor axis orientation and just below the centerline of the block, threaded to match the pitch of a small diameter lead screw that was around 12" long. The lead screw was gear driven by another 6v DC motor via a hard plastic gear reduction box.

There were two of these lead screw driven mechanisms in parallel right next with each other, mounted in a flat-black painted, 3/4" thick MDF box. Opposite ends of the box had 2" diameter holes cut in them that the laser beam passed through. These ends were removable to service the chopper mechanism. One chopper motor's notched disc had 36 teeth, the other 18 teeth and could be independently moved into and out of the beam path of the laser head that led to the projector optics and beam distributions. Very old school, eh? With both chopper discs in the beam at the same time but running at harmonically different speeds some interesting chopper effects were had but usually just one was used at a time.

The lead screw mechanisms were actually purchased from Radio Shack for about $1 a piece. It ran off 2 C cell batteries. Their original purpose was to provide youth who were learning to read a variable speed, slow moving .5" x 10" thin, black plastic, horizontal strip that clips on the lead screw and travels down the page supposedly to help the child learn to pace their reading pages of text.

I originally used these lead screw mechanisms to move my round,50mm diffraction gratings and larger lumia discs into and out of beam paths of the scanners or dedicated lumia beams. But they were just too loud in the 40' planetarium. The beam chopper mechanisms sat behind the rear wall of the planetarium theater and could not be heard at all.

I bet you're sorry you asked...