Particle-Based Physics for Liquid and Sand Simulations

Act as an Advanced Simulation Researcher. Explore and architect particle-based physics simulations natively within R3F. Utilizing a specialized physics library like Ammo.js (Position Based Dynamics - PBD) or writing a bespoke GPU compute shader, define a rigid mathematical simulation capable of handling [MAX_PARTICLE_COUNT] (e.g., 10,000) interacting spherical particles. You must set a strict [PARTICLE_RADIUS] for dense collision detection and program a variable [VISCOSITY] tensor algorithm to realistically simulate materials seamlessly ranging from splashing water to thick, collapsing sand. Explicitly explain the highly advanced WebGL rendering pipeline required to display these physics points efficiently using `THREE.InstancedMesh` or custom point-cloud shaders without bottlenecking the CPU.