Large-scale crowd simulation in real-scene 3D models based on oblique photography

Building on prior work that developed an integrated model for simulating interactions between biological clusters (e.g., crowds) and fluid particles (e.g., water flow), this study advances both the theoretical framework and practical applications of such simulations. The original model established a unified dynamic force field encompassing the behavior of biological entities, various fluid types, and their interactions, with a primary focus on crowd evacuation during sudden flood events. Additionally, scenarios involving whirlpools and abrupt water level changes (e.g., waterfalls) were studied to inform effective survival strategies. However, there are still some deficiencies in the previous work. In terms of scene scale and authenticity, it needs to be improved. In terms of group-driven strategies, it also needs to be extended to three-dimensional space. The number of particle types and the interaction between different types of particles also need to be further expanded. This study extends the framework to cover more complex disaster scenarios, including earthquakes and landslides, by incorporating real-scene 3D modeling through drone-based oblique photography. The resulting elevation, texture, and mesh data are processed using a lightweight 3D reconstruction approach to reduce computational load. A cage-type projection separation method is proposed for isolating ground objects, along with a novel particle replacement algorithm for modeling solid-state objects. For large-scale crowd simulation, several new strategies are introduced, including the variable-rotation method, centroid-following method, crowd center method, and neighborhood extreme value method—each inspired by real-world observations. Furthermore, cross-species particle flow fusion has been expanded to include both solid-state and biological fluids, forming the basis of a new multi-type particle fusion computing concept. Two real-scene 3D models—an earthquake zone and a landslide site—were used as case studies to construct a visual prototype system for crowd simulation. Experimental results demonstrate the feasibility and effectiveness of the proposed 3D modeling techniques, simulation methods, and fusion algorithms, confirming their potential for realistic and efficient disaster response simulations.