How Difference clouds makes glowing veins of light

Anyone who has used a photo editor may know the difference clouds filter, which makes marbled, vein-like patterns out of random noise. Difference clouds in Screensavers by Zaweba takes that idea and sets it moving. Glowing veins of light ripple slowly through the dark, forming, thinning and joining again, and the result is one of the most hypnotic scenes in the app.

It belongs to the night pack, the set of dark screensavers with a few bright moving things in them. Most of the screen stays dark, and only the veins catch the eye.

How the picture is made

Two layers of noise drift across each other. Noise here means a smooth, cloudy pattern of light and dark made by a formula, a little like a satellite view of clouds. When the two layers are combined, the places where they nearly match turn into thin bright lines, and everywhere else falls away into darkness. As the layers drift, the lines move, so the veins seem to flow and crawl across the screen.

The pattern is worked out on a small grid and then stretched to fill the screen. That keeps the processor work low, which matters for a screensaver that may run for hours, and it gives the veins their soft, glowing edges. Everything is drawn by the app's own code.

Colours, speed and detail

Colours has five choices. Moonlit greys is the most restrained, silver light in the dark, and suits almost any room. Violet night is cool and dreamy. Embers turns the veins into the orange glow of a dying fire, which is lovely on a winter evening. Deep teal is calm and watery. Changing slowly drifts between colours over time, for a screen that will be idle for a long stretch.

Speed runs from 1 to 10 and sets how quickly the layers drift, and so how fast the veins move. At the low end the movement is barely noticeable unless you watch. At the top the pattern churns.

Detail, also 1 to 10, sets how fine the pattern is. Low detail gives broad, smooth shapes with a few large veins. High detail gives a finer web of thinner lines. Fine detail looks best on a large, sharp monitor; on a small laptop screen a lower setting keeps the veins clear.

Choosing a look in the manager

The manager's live preview follows each change, so it's easy to experiment. Choose the colours first, then detail, then speed. A slow speed with medium detail and moonlit greys is a good, quiet starting point. Embers with low detail and a slightly faster speed looks more like fire.

Then press Preview full screen. Abstract patterns change character a lot at full size, and the detail setting in particular is hard to judge in a small window. Moving the mouse or pressing a key ends the preview.

Setting it as your screensaver

Use this screensaver builds it into your profile with no administrator rights needed, then opens Windows' Screen Saver Settings for the wait time and the password option. The settings are read whenever the screensaver starts, so you can come back and change the colours whenever you like.

On several monitors you can run one on each screen, stretch one across them all or keep it on the main monitor with the rest black. Stretched, the veins flow from one screen to the next as one pattern.

Where it fits and what to avoid

Because it is mostly dark, Difference clouds is a good choice for a bedroom or a dim room where a bright screensaver would light up the walls. It also sits well with Aurora and Deep space if you tick them together in Install several for a random pick.

Avoid very high detail with a very high speed, which can turn the pattern into flicker. And if the veins look too faint in a lit room, try a brighter colour scheme rather than more detail.