The geometry is BodyParts3D (© DBCLS, CC BY-SA 2.1 JP) — 45,879 triangles of real heart, with the great vessels carved from the same body scan. The beat is not a loop: every vertex has an activation time built from real conduction velocities — about 1 m/s across the atria, a deliberate 0.1 s hold at the AV node, then 2–4 m/s down the Purkinje fibres — and the trace is that same clock read as a lead II ECG. Arteries and veins each pulse on their own waveform — the arterial pressure wave, and the jugular a–c–v trace, which is driven by the atria and is a fraction of the size. FIBRESdraws the epicardial muscle helix at its real angle, about 60° to the circumference — two opposed helices shortening at once is why a ventricle wrings rather than simply squeezing.

One honest caveat: this scan is a single closed outer surface and has no interior. So the valves, septum, papillary muscles and chordae under INSIDE are drawn, not measured — placed where those structures sit and moving on the schedule they really move on, in a paler material so you can always tell which parts of this page are scan and which are diagram. The four chambers are a positional approximation: this scan is one welded surface with no internal septum, so they are divided at the midline and the atrioventricular groove. Drag to turn it, scroll to zoom.