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"Since 1999, I have been the proprietor of DNA Lounge, a world famous and award-winning all ages dance club and live music venue in San Francisco. I am also the developer of XScreenSaver, the standard screen saver collection shipped on most Linux and Unix systems running the X11 Window System. I released the first version in 1992. I ported it to MacOS X in 2006, to iOS in 2012 and to Android in 2015. On X11 systems, XScreenSaver is two things: it is both a large collection of screen savers; and it is also the framework for blanking and locking the screen. On MacOS systems, these screen savers work with the usual MacOS screen saving framework (X11 is not required). On iOS and Android devices, it is an application that lets you run each of the demos manually.

Some of my screen savers originated as visualizations of some kind of mathematical principle, like, say, geodesics, moebius strips or fractals, or even just interfering sine waves, and I just mess around with it until the visualization looks interesting. Often choosing the proper algorithm for generating the color palette is key to making it look cool.

More often, though, I tend to build simulations of real or hypothetical objects. For example, simulating a realistic looking lava lamp without doing a full simulation of its fluid dynamics. The trick for simulations like that tends to be to think of the right shortcut that will look realistic while in fact doing something much less complex than the real world physics. (This was far more important in years past, thanks to Moore's Law.)

And sometimes the savers come from "I wonder what it would look like if...", like, the way Splodesic ejects and reabsorbs the triangles comprising its surface. The idea I had in my head for that looked a bit different than how the implementation ended up behaving, but I was quite happy with what came out.

When I build simulations of objects, realistic looking or otherwise, I almost always do it generatively. I make very little use of hand-built 3D models, but instead generate almost everything from first principles, usually starting with cosine. That just feels more pure to me.

I tend to put a lot of work into making the movements of objects and their components feel organic rather than mechanical and linear. I also try to make the behaviors be somewhat calm rather than twitchy. Just because you can achieve a frame rate that moves things around really fast doesn't mean that's going to be the best looking result.

A few months ago I wrote in some detail about the process behind some recent savers, which I guess answers this question in a more specific way about a few of them.

It varies widely. Sometimes they come out just like I envisioned, but often I will tweak things as I go, or accidentally stumble across some variation that looks better, that might be nothing like where I started.

Since XScreenSaver is very old code, and It runs on many different platforms, the most challenging part is always just keeping it all running, and portable. Since some of the shared frameworks underlying my savers date back to 1991, there are quite a few compatibility layers inside there.

One of the things I like best about writing screen savers is that once they are finished, they pretty much are finished. There the old joke, "The software isn't complete until it's last user is dead", but in the case of a screen saver, there's rarely a version 2. It does it's thing and mostly just keeps doing it. Unlike most other software there tends not to be a lot of maintenance.

Keeping the underlying infrastructure running tends to require ongoing maintenance, but the savers themselves tend to be stable.

I wrote a very long article about what was involved in porting XScreenSaver to MacOS and iOS, which was certainly one of the bigger challenges.

I wouldn't say I was surprised at how popular it was, since it was the first such thing available for Unix. In the early days I was somewhat surprised, and pleased, at how many other people contributed code to it. Working with other people and integrating their contributions has been fun, and made the package better as a whole. Unfortunately, the rate of outside contributions has decreased a lot of late. I don't have a theory as to why. Maybe it's because they don't teach C any more.

What are some of your favorite screensavers (apart from your own)

ElectroPaint by David Tristram, which I first saw on an SGI in 1991 or 1992 is to this day one of my favorites. It was a big inspiration. The original After Dark Mac savers from the mid 80s were also just so much fun. And of course the Amiga "Boing" demo. I've also long been a fan of Electric Sheep by Scott Draves.

I also tend to enjoy the sort of savers that do fan-service simulations of effects from sci-fi movies and TV, like the savers that reproduce the behaviors of HAL 9000, the Star Trek LCARS displays, the Stargate Dialing Simulator, etc. I enjoy them most when they are clearly generative rather than just slideshows or movies: anybody can hit record, but creating it from whole cloth is the cool part.

(In fact, I find it distressing when people package up a slideshow of photos and call that a "screen saver". That's no screen saver. It cheapens the term. It's just a photo album.)

I was also always impressed by any of the "Demoscene" work I ran across back In the day, though I was never involved in that world directly, not having been a 286/386 hacker.

Of course! XScreenSaver, set to select one at random.

Any time some pedantic jerk says "YOU KNOW, screen savers aren't really NECESSARY with modern monitors" I want to ask them "How awful is it to have been born without a soul?" Screen savers are art. As long as computers have screens, people will make art for them. I also find it amusing when I am in an art museum or gallery and see a "digital installation" where the only difference between that work and a "screen saver" is that they wrote an "artist's statement" about how it explores the dichotomy between whatever -- and/or someone gave them a grant for it."