FracFusion: A Heterogeneous Simulation-Rendering Framework for Vehicle Impact and Structural Breakage

High‑fidelity simulation of simultaneous structural breakage in vehicle‑obstacle collisions is critical for autonomous‑driving safety testing and neural world modeling. Real crash data is scarce and costly to acquire, making simulation the main source of diverse accident scenarios. Existing pipelines face a fundamental trade‑off: node‑beam solvers capture realistic vehicle‑component structural fracture but cannot generate arbitrary continuum fragmentation for obstacles, whereas MPM‑based 3D Gaussian Splatting (3DGS) produces debris but discards calibrated vehicle mechanics when vehicles are converted to particles. Naively combining solvers cannot resolve heterogeneous contact, consistent bidirectional momentum transfer, and persistent inter‑penetration artifacts. We present FracFusion, a heterogeneous simulation‑rendering framework. It keeps calibrated node‑beam vehicle assets intact and uses MPM‑augmented 3DGS for photorealistic brittle obstacle fracture. Lightweight shell proxy particles enable stable bidirectional impulse coupling within Collision‑MPM without redundant vehicle dynamics. We further incorporate particle‑triangle anti‑penetration correction and physics‑aware depth compositing to mitigate cross‑representation artifacts. Experiments and ablations validate our design. Physical checks verify momentum and energy stability under high‑energy impacts, and perceptual studies show improved visual plausibility. FracFusion delivers crash simulation featuring both vehicle‑component structural fracture and obstacle continuum fragmentation for safety‑critical autonomous simulation and world‑model applications.