Liquid Metal Field

About this background

Metaballs look like a physics problem and are actually a filter problem. Blur a set of shapes hard enough that their edges overlap, then push alpha through a steep contrast curve, and the overlapping region sums past the threshold and snaps into a single fused silhouette while everything else falls away — one `feColorMatrix` replaces an entire particle system, and it runs on the GPU. The numbers in that matrix are the tuning knobs worth understanding: multiplying alpha by nineteen and subtracting nine puts the cutoff near 0.47, so a smaller multiplier keeps the blobs distinct and a larger one makes them reach for each other from further away. Two details separate this from the version that circulates as a CodePen. The circles are filled with a gradient rather than a flat color, and a radial white highlight sits over the whole field in overlay blend mode — that specular sheen is the difference between liquid metal and blue blobs. The trap to avoid: SVG filter ids are document-global, so the id has to come from `useId`, or a second instance silently hijacks the first one's filter.