Print the barcode cards and lay them flat on the desk. Every card has the same edge
length d. In AR, each +q / −q charge floats
2d above its card, and each ±2q plate stands as a 4d × 4d board upright on the desk.
①Print the marker sheet at 100% and cut out the cards.
②Start the camera and hold steady — the layout locks automatically, so the field stays rigid (no jitter) while you move.
③Toggle Field lines, Shells (3-D equipotential surfaces — this view hides the desk and follows the camera, with gyro fallback) and Relief (the desk rises to height ∝ V, with equal-ΔV contour rings). Shells and Relief are one-at-a-time — switching one on switches the other off.
Camera needs HTTPS · field lines: 16 per unit charge · equipotentials: equal ΔV steps.
No camera to hand? Test with a photo of the printed cards — it runs through the exact AR pipeline.