Technique · Fields

Metaballs

Soft blobs that merge and pinch apart like wax in a lava lamp, shaded as lava, glass or ink.

Metaballs 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

  • Surface tension pulls a liquid into the shape with the least surface for its volume, which is why drops of mercury, wax or water on a flat surface join as soon as they touch.
  • Metaballs were developed in the 1980s: Jim Blinn used a Gaussian field for molecules in 1982, and a Japanese group coined the name metaballs in 1985.
  • Liquid light shows of the late 1960s, such as the Joshua Light Show at the Fillmore East in New York, projected moving oil and dye between glass dishes in a similar blobby style.
  • The lava lamp, invented by the British inventor Edward Craven Walker in 1963, works because a wax warms at the bottom, becomes lighter than the liquid around it, and rises in blobs that cool and sink again.
  • Computer graphics researchers used blobby surfaces like these in the 1980s to draw molecules and soft organic shapes; Jim Blinn published his version in 1982.

The mathematics

  • Each ball adds (r / d) to the power 2.40 and the blob is where the total is 1; two equal balls therefore join once their centres are closer than about 2.67 radii, though they would only touch at 2 radii.
  • The surface is an implicit surface, f(x, y) = 1, rather than a list of points; to light it the program finds the slope of f, since the surface normal is the gradient.
  • Every ball adds a little to the field everywhere, which is why a surface bulges toward its neighbours before they actually touch.

In art

  • The psychedelic posters and light shows of the late 1960s made flowing blobs of colour a symbol of the era, and the lava lamp is the household version.
  • Soft, merging forms are a recurring theme in modern animation, from title sequences to the screensaver, because they look alive without being any particular creature.

More ways to use it

Related techniques

Nebula and stars · Liquid · Droplets · Network · Terrain and maps · Neuron · Order to chaos · Fractal tree

All 90 techniques