Technique · Fields
Banded agate
Flowing ribbons of stone, bubble foam, amber, green and pale glass, traced with fine loops and bevelled like polished resin.
Banded agate 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
- Agate forms when silica-rich water seeps into a gas bubble or crack in volcanic rock and deposits layers of microscopic quartz fibres, one after another; the bands are those layers.
- Iron oxides colour agate red, brown and yellow, and minerals such as chlorite can colour it green.
- Idar-Oberstein in Germany was a centre of agate cutting for centuries and later worked agate imported from Brazil.
- Much agate sold today is dyed, because the stone is porous enough to take colour along its bands.
- Agate is a banded form of microcrystalline quartz, chalcedony, that grows layer by layer from silica-rich water filling cavities in rock.
The mathematics
- Each ribbon edge is a level set: the places where one smooth coordinate crosses a fixed value, which is why edges never cross and nest like the rings of a tree.
- The foam is a Voronoi diagram: each bubble is the set of points nearer to its own seed than to any other, so every wall falls exactly halfway between neighbours.
- The fine strands are contours of a noise field added to the ribbon coordinate: where the noise is flat they run parallel to the ribbons, and around a peak they close into loops.
In art
- Cut and polished agate slices were a staple of nineteenth-century jewellery and ornament.
- The same flowing bands are the basis of marbled paper, where ink on water does what silica does in rock.
More ways to use it
Related techniques
Nebula and stars · Liquid · Droplets · Network · Terrain and maps · Neuron · Order to chaos · Fractal tree