What is the difference between simplex noise and Perlin noise?

Both are smooth gradient noises. Simplex noise samples on a triangular lattice instead of a square grid, which removes the visible axis-aligned artefacts of classic Perlin noise and is cheaper to compute in three dimensions, which is why it is used here.

Is the Simplex Drift screensaver free?

Yes. It runs free in your browser with nothing to download or install, and it works offline once the page has loaded.

What does the Seed setting do?

Everything is deterministic from the seed: the noise table, where the field’s features land and the order particles spawn in. Leave it blank for a fresh random layout on every run, or type any short word or number to get the same layout back each time.

Why does the image ripple when I move the mouse?

The cursor and a lagging echo of it act as two wave sources. Their interference pattern nudges nearby particles onto the bright fringes and dims the dark ones, so the flow visibly reacts to you. Turn off Cursor ripples in the settings if you want the field left alone.

How do I exit the Simplex Drift screensaver?

Press the ESC key at any time to leave fullscreen and return to the page.

Is simplex noise random?

It is deterministic: the same input always gives the same output. It looks random but is smooth, because nearby inputs produce nearby values.

The n-dimensional version of a triangle: a triangle in 2D, a tetrahedron in 3D. An n-dimensional simplex has n+1 corners.

Was simplex noise patented?

A US patent (6,867,776) covered certain implementations in three or more dimensions. It expired on 8 January 2022.

Simplex Drift Screensaver

Simplex Drift is a free, in-browser screensaver and the original Driftfield look: thousands of particles read 3D simplex noise directly as a compass heading and wander the smooth currents it makes. The third noise axis slowly advances, so the whole field rotates and reforms without ever repeating. Nothing to download, and ESC exits at any time.

How the Simplex Drift screensaver works

Simplex noise is a smooth random function: nearby inputs give nearby outputs, with no grid artefacts. This saver evaluates 3D simplex noise at every particle’s position and multiplies the result by two full turns to get an angle. Because the noise is smooth, neighbouring particles get nearby angles, and the field forms wide, coherent currents.

The third noise coordinate is time. The Evolve slider sets how fast the field slides along that axis, so currents that were flowing east slowly swing north and then somewhere new. At zero the field freezes and the particles settle into fixed channels.

Particles accelerate toward their heading with damping rather than snapping to it, which rounds off every corner into a curve. Each one draws a short segment per frame; the previous frame fades toward the background at the rate set by Trail, so those segments accumulate into ribbons of light.

Colours come from a second, very low-frequency noise read at spawn time. Particles born near each other share a hue, which is why the image bands into painted regions rather than scattering into confetti. Detail scales the spatial frequency: low is broad and sweeping, high is tight and turbulent.

Why simplex noise replaced Perlin noise

Ken Perlin created gradient noise in 1983 because computer-generated imagery looked machine-like; he had worked on Disney’s Tron (1982) beforehand, and he described the method in a 1985 SIGGRAPH paper and later received an Academy Award for Technical Achievement for it. Classic noise interpolates between gradients on a hypercubic grid and can show faint directional artefacts.

In 2001 Perlin designed simplex noise to overcome limits of the classic function, especially in higher dimensions. Instead of a cubic grid it divides space into simplices, the n-dimensional analogue of a triangle: triangles in 2D, tetrahedra in 3D. A simplex has n+1 corners where a hypercube has 2^n, so far fewer contributions are summed, and the cost grows as O(n²) instead of O(n·2^n).

For a particle display, the useful result is that simplex noise has no noticeable directional artefacts, so reading it as an angle gives swirling currents with no visible grid. A US patent (6,867,776) covered some implementations in three or more dimensions; it expired on 8 January 2022.

A worked example

At the defaults — Aurora palette, 2000 particles, Speed 1, Trail 62, Detail 1.2, Evolve 1 — the screen fills with slow green and violet currents a few hundred pixels wide that gradually swing direction. Push Detail to 3 and the same particles break into tight, curling eddies; drop Trail to 20 and they become brief comets instead of ribbons.

Settings & tips

Type a seed such as abcd to get the same currents back every time; leave it blank for a fresh layout on each run.
Blend in Curl noise at around 40% to stop the currents pooling in the noise field’s sinks.
The Bone palette is the one light option: dark ink on a warm paper background, drawn without additive glow.

Frequently asked questions

What is the difference between simplex noise and Perlin noise?: Both are smooth gradient noises. Simplex noise samples on a triangular lattice instead of a square grid, which removes the visible axis-aligned artefacts of classic Perlin noise and is cheaper to compute in three dimensions, which is why it is used here.
Is the Simplex Drift screensaver free?: Yes. It runs free in your browser with nothing to download or install, and it works offline once the page has loaded.
What does the Seed setting do?: Everything is deterministic from the seed: the noise table, where the field’s features land and the order particles spawn in. Leave it blank for a fresh random layout on every run, or type any short word or number to get the same layout back each time.
Why does the image ripple when I move the mouse?: The cursor and a lagging echo of it act as two wave sources. Their interference pattern nudges nearby particles onto the bright fringes and dims the dark ones, so the flow visibly reacts to you. Turn off Cursor ripples in the settings if you want the field left alone.
How do I exit the Simplex Drift screensaver?: Press the ESC key at any time to leave fullscreen and return to the page.
Is simplex noise random?: It is deterministic: the same input always gives the same output. It looks random but is smooth, because nearby inputs produce nearby values.
What is a simplex?: The n-dimensional version of a triangle: a triangle in 2D, a tetrahedron in 3D. An n-dimensional simplex has n+1 corners.
Was simplex noise patented?: A US patent (6,867,776) covered certain implementations in three or more dimensions. It expired on 8 January 2022.

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