Implementing Soft Body Physics and Cloth Simulation

Act as a Technical Simulation Artist. Provide a grueling, line-by-line technical walkthrough for integrating genuine soft body physics (cloth simulation) directly into a React Three Fiber scene. Focus the architecture on creating a highly reactive cloth membrane mapped to a complex [MESH_RESOLUTION] geometric grid. You must mathematically configure the [SOLVER_ITERATIONS] to perfectly balance visual collision accuracy against catastrophic CPU throttling, and define a precise [STIFFNESS_COEFFICIENT] dictating whether the material behaves like heavy leather or light silk. Explicitly show the complex vertex-mapping logic required to continuously extract the physics particle positions and dynamically inject them back into the Three.js `BufferGeometry` position attributes on every single frame.