Tophi Formation and Dissolution in Three Dimensions
This is the 3D companion to the 2D Tophi Formation & Dissolution Simulator, rendered in real WebGL with an orbitable camera instead of a flat top-down canvas. The chalky tophus mass, its radial shell of needle-shaped MSU crystals, the macrophages that clear it, and the inflammatory flares it triggers are all placed in true 3D space around a joint, so their depth and packing can be inspected from any angle instead of only from directly above.
The underlying kinetics are ported verbatim from the 2D original: a solubility threshold of 6.8 mg/dL for monosodium urate (MSU) separates a supersaturated regime, where tophus volume grows with drive × months × 2.2, from an undersaturated regime, where volume decays exponentially with a per-month rate constant of 0.018 × (6.8 − urate). The same two sliders — months on urate-lowering therapy and serum urate level — drive both the numeric readouts and every object in the 3D scene: the tophus core's radius, the crystal count and their scatter distance, whether macrophages appear, and whether inflammatory flares fire.
What's new in the 3D view
A crystal cluster spread control pulls the needle crystals outward from the tophus core so their individual geometry is visible instead of being packed into a single mass — useful for seeing how many crystals the current volume implies. An auto-rotate speed control spins the whole scene for a hands-free view, independent of manual drag-orbit and scroll-zoom camera control.
- 6.8 mg/dL: Solubility threshold — the same SAT constant used in the 2D original
- 0.018 × drive: Per-month dissolution rate constant when undersaturated
- drive × months × 2.2: Growth term when supersaturated
- 320%: Volume cap, matching the 2D original's ceiling