Technique · Fields
Nebula and stars
Warped fractal clouds, dark dust lanes and a star field with diffraction spikes.
Nebula and stars is a field drawn for every pixel by the graphics chip. Every piece on Synapse Drip is made from a recipe that layers techniques like this one, and you can change any of it in the Studio.
Good to know
- The Orion Nebula, about 1,300 light years away, is bright enough to see without a telescope: it is the fuzzy middle "star" in Orion's sword.
- The dark lanes in a nebula are dust grains about as small as the particles in smoke; they block the light behind them, and they are also the raw material for new planets.
- The colours in many space-telescope pictures are chosen by the astronomers: Hubble's famous Pillars of Creation maps sulphur, hydrogen and oxygen light to red, green and blue.
- A cloud of gas collapses into stars when its own gravity beats its pressure; in a stellar nursery thousands of stars can begin forming within a few million years.
- Real emission nebulae glow because ultraviolet light from young, hot stars knocks electrons off hydrogen atoms; the red in astronomical photographs is hydrogen-alpha light at 656 nanometres.
- The cross-shaped spikes on bright stars are an artefact of the telescope: they come from the struts that hold its secondary mirror, not from the stars.
- Fractal Brownian motion adds noise at twice the frequency and half the strength, again and again; clouds, coastlines and nebulae share that signature.
The mathematics
- Each octave of noise has twice the frequency and half the strength of the one before, so the strengths sum to 1 + 1/2 + 1/4 + ... = 2: more octaves add fine detail without making the cloud brighter.
- Domain warping feeds noise into the coordinates of more noise, which turns gentle blobs into folded, billowing clouds; the shape is a function of position alone, so it is the same on every screen.
- Stars are placed by hashing the integer coordinates of each cell of a grid, so the field is endless and exact, and no star is ever stored.
In art
- Astronomical pictures sit between science and painting: choices about colour and contrast decide what a viewer notices first.
- Romantic painters such as J. M. W. Turner painted skies as luminous masses of colour; a nebula made of numbers is the same ambition by other means.
More ways to use it
Related techniques
Liquid · Droplets · Network · Terrain and maps · Neuron · Order to chaos · Fractal tree · Radiolarian shell