What it does
Melts the image into rounded liquid blobs that flow and merge like drops of ink.
Metaballs were invented to draw molecules. Jim Blinn needed atoms that fused smoothly into electron-cloud surfaces for Carl Sagan’s Cosmos in the late 1970s, so instead of drawing spheres he gave each atom a field, summed the fields, and rendered the surface where the total crossed a threshold. The trick escaped chemistry immediately. Demoscene coders made metaballs a rite of passage in the 1990s, motion designers turned them into lava lamps and ferrofluid, and the same math now sits behind every gooey logo and liquid blob loop on the internet.
The merging is not an effect layered on top; it falls straight out of the math. Two balls far apart each cross the threshold alone, two perfect circles. Bring them closer and their fields begin to add in the gap between them, the sum crosses the threshold there too, and a bridge forms, thin at first, then swelling until the pair reads as one shape. Nothing was blurred and nothing was interpolated: the surface simply follows the field, which is why the necking, kissing, and pinching look physical.
The Metablobs effect uses the image itself as the source of the balls. It samples the frame on a grid and plants a blob wherever a cell matches a chosen brightness or color, so the bright side of a face, a moving hand, or a red jacket becomes a colony of blobs that tracks the footage. The colony can float on transparency, sit on a flat color, or melt back over the original frame, and dialing the merge from tight to gooey takes the same source from crisp dots to one slow amoeba.
Signature looks
Lava lamp
Large, slow, fully merged blobs tracking the bright regions of the footage. The frame breathes as shapes fuse and split, the screensaver that never gets old.
Ink droplets
Small blobs at low merge, hovering just at the edge of contact. Neighbors kiss, neck, and pull apart as the source moves, the surface-tension look.
Chroma pool
Blobs keyed to a single color instead of brightness, so one hue detaches from the frame and pools into liquid while everything else stays put.
Try it on your own footage
This effect runs live in the Modulate editor, with layers, effect chains, masks, and keyframes. Free, no signup, nothing to install.
Common questions
What are metaballs?
Blobby shapes defined by a scalar field rather than a boundary. Every ball contributes influence that decays with distance, the contributions sum, and the rendered shape is the iso-line where the summed field crosses a threshold. Because nearby balls reinforce each other’s fields, they merge smoothly into one shape as they approach, which is the behavior metaballs are famous for.
Who invented metaballs?
Jim Blinn developed the technique, often called blobby molecules, at JPL around 1980 to render molecular surfaces for Carl Sagan’s Cosmos: atoms as summed density fields rather than hard spheres, so bonded atoms fused the way electron clouds do. Variants followed under different names, including soft objects and, in Japan, the meta-ball spelling that stuck.
Why do metaballs merge?
Because the shape is a threshold on a summed field, not an outline. When two balls are close, the space between them receives influence from both, and the combined value can cross the threshold even where neither ball would alone. The surface has no idea it was ever two objects; it just traces where the total field is strong enough, so bridges form and dissolve naturally.
What is the difference between metaballs and Voronoi cells?
They are near opposites built from the same ingredient, distance. Voronoi partitions space by which seed point is nearest, producing hard-edged cells that tile the plane with straight shared walls. Metaballs sum smooth fields around the seeds and threshold the total, producing round, merging blobs with no walls at all. One divides, the other fuses.
How do you make a metaball animation?
The classic way is to animate ball positions by hand and render the field. Modulate skips the keyframing: the Metablobs effect derives its blobs from your image or video, matching by brightness or color, so the animation comes from the footage itself. It runs live in the browser, and the blobs can sit over the original frame, a flat color, or transparency.
Related effects
Field effect
Generates an evolving procedural field — drifting clouds, marbled veins, swirling flow, or Voronoi cells.
Contour effect
Traces the light and dark regions of the image as evenly spaced lines, like a topographic map.
Blob tracking
Finds regions of the image by color, motion, or edges and draws boxes, markers, and labels around them.
Halftone effect
Turns the image into printed dot patterns, from single-color newspaper dots to full four-ink color screens.