This is the same real physics as the 2D Schwinger-effect simulator, rendered as a free-orbit 3D field region between two capacitor plates. A strong electric field spans the gap along a fixed axis, and the vacuum inside spontaneously produces real electron-positron pairs via quantum tunnelling through the mass gap — the true Sauter-Schwinger effect, not an artistic stand-in. Instanced electron (blue) and positron (red) pairs spawn at random points inside the field volume and stream apart along the field lines the moment they tunnel into existence, with spawn density governed by the genuine exponentially-suppressed rate Γ/V ∝ E²·exp(−π·Ec/E), worked in the normalized ratio E/Ec so the real exponential survives in floating point. Tune the field from a small fraction of the true QED critical field Ec ≈ 1.3×10¹⁸ V/m up past it and watch the field volume go from essentially empty to dense with newly-real pairs — the genuine tunnelling threshold, viewable from any angle.