Editing Crowd simulation (section)

== Crowd dynamics ==
One of the major goals in crowd simulation is to steer crowds realistically and recreate human dynamic behaviors.

There exists several overarching approaches to crowd simulation and AI, each one providing advantages and disadvantages based on crowd size and time scale. Time scale refers to how the objective of the simulation also affects the length of the simulation. For example, researching social questions such as how ideologies are spread amongst a population will result in a much longer running simulation since such an event can span up to months or years. Using those two characteristics, researchers have attempted to apply classifications to better evaluate and organize existing crowd simulators.<ref>{{cite journal |doi=10.1145/1842722.1842725 |title=Crowd modeling and simulation technologies |journal=ACM Transactions on Modeling and Computer Simulation |volume=20 |issue=4 |pages=1–35 |year=2010 |last1=Zhou |first1=Suiping |last2=Chen |first2=Dan |last3=Cai |first3=Wentong |last4=Luo |first4=Linbo |last5=Low |first5=Malcolm Yoke Hean |last6=Tian |first6=Feng |last7=Tay |first7=Victor Su-Han |last8=Ong |first8=Darren Wee Sze |last9=Hamilton |first9=Benjamin D. |hdl=10149/118022 |url=https://research.tees.ac.uk/ws/files/6477586/Accepted_manuscript.pdf }}</ref>

;Flow-based Approach: Flow based crowd simulations focus on the crowd as a whole rather than its components. As such individuals do not have any distinctive behaviors that occur due to input from their surroundings and behavioral factors are largely reduced.<ref name="Degond">{{cite journal |last1=Degond |first1=Pierre |last2=Navoret |first2=Laurent |last3=Bon |first3=Richard |last4=Sanchez |first4=David |title=Congestion in a Macroscopic Model of Self-driven Particles Modeling Gregariousness |journal=Journal of Statistical Physics |date=February 2010 |volume=138 |issue=1–3 |pages=85–125 |doi=10.1007/s10955-009-9879-x |arxiv=0908.1817 |bibcode=2010JSP...138...85D }}</ref> This model is mainly used to estimate the flow of movement of a large and dense crowd in a given environment. Best used in studying large crowd, short time objectives.

;Entity-based Approach: Models that implement a set of physical, predefined, and global laws meant to simulate social/psychological factors that occur in individuals that are a part of a crowd fall under this category. Entities in this case do not have the capacity to, in a sense, think for themselves. All movements are determined by the global laws being enforced on them. Simulations that use this model often do so to research crowd dynamics such as jamming and flocking. Small to medium-sized crowds with short term objectives fit this approach best.

;Agent-based Approach: Characterized by autonomous, interacting individuals.<ref name="AP">{{cite journal |last1=Shao |first1=Wei |last2=Terzopoulos |first2=Demetri |title=Autonomous pedestrians |journal=Graphical Models |date=September 2007 |volume=69 |issue=5–6 |pages=246–274 |doi=10.1016/j.gmod.2007.09.001 }}</ref> Each agent of a crowd in this approach, is given a degree of intelligence; they can react to each situation on their own based on a set of decision rules. Information used to decide on an action is obtained locally from the agent's' surroundings. Most often, this approach is used for simulating realistic crowd behavior as the researcher is given complete freedom to implement any behaviors.