Experiment № 033 · The story
Metaballs
Why I picked it
I wanted the opposite of a hard edge. Most shapes I draw are defined by their outline — you set the border and fill it in. Metaballs turn that inside out: nothing here has an edge of its own. Each blob is only a soft glow of influence spreading out from a point, strongest at the centre and fading with distance. The outline you see is never drawn directly — it's discovered, by asking every spot on the screen "how much total glow is landing here?" and drawing a line exactly where that sum crosses one chosen level. Two blobs drifting together don't collide; their glows simply add, the sum climbs over the line in the gap between them, and a smooth neck of skin reaches across to join them. It's the closest thing I know to watching soap bubbles decide to merge.
What I enjoy about it
The whole outline is drawn by marching squares, and I love how humble the trick is. Lay a coarse grid over the field and, at each grid corner, note one bit: is the glow here above the threshold, or below? Four corners, so sixteen possible on/off patterns per cell — and each of those sixteen patterns maps, by a tiny lookup table, to a fixed way of slicing the cell with a line. String those little segments across the whole grid and a single unbroken contour falls out, wrapping every blob and every merge. No blob is ever asked what shape it is; the shape is a by-product of a threshold and a table. Turn the grid resolution down and you can watch the smooth curves shatter into honest little facets — the seams of the machine showing through. Flip the grid overlay on and you can literally see the corners voting.
Something you might take away
A boundary doesn't have to be a thing you place — it can be a level you choose. The blobs never touch; what makes them look joined is that I picked one number and called everything above it "inside." Nudge that threshold and the same field grows a thicker skin, or the necks between blobs thin out and snap. So much of how we carve the world into separate things works this way: the objects are continuous fields of influence, and the line between "one thing" and "two things" is a cutoff we set, not a fact we find. Move the cutoff and the count of things changes, without anything in the world having moved at all.