The lab
Metaballs
Metaballs are implicit surfaces defined by a scalar field. Each blob emits a field that falls off with the square of distance. Where the combined field of nearby blobs exceeds a threshold, the surface appears — producing smooth, organic merging and splitting that looks almost alive.
f(x,y) = Σ r² / ((x−xᵢ)² + (y−yᵢ)²) · surface where f ≥ threshold
8
40
1.0
1.0
click to add a blob at cursor position
The metaball technique was invented by Jim Blinn in 1982, originally for rendering molecular electron density clouds. The key insight is beautifully simple: instead of defining surfaces explicitly with vertices and polygons, you define a scalar field in space and draw the isosurface where that field crosses a threshold. Because the field contributions from nearby sources add smoothly, the surfaces merge and separate with a natural, organic quality that is very difficult to achieve with conventional geometry.
This visualization computes the field at every pixel on a downsampled grid. In gradient mode, pixel brightness maps directly to field strength, producing the characteristic glowing blob appearance. In contour mode, thin isolines are drawn at fixed field values, revealing the underlying topology of the scalar field — concentric rings around each blob that deform and merge as the blobs interact.
Metaballs have found widespread use in computer graphics, from the blobby lava-lamp aesthetics of 1990s demos to modern fluid simulations and medical imaging. The same mathematics underlies marching cubes and marching squares algorithms used throughout scientific visualization.