Modifications for dense crowds

All the features outlined until now are general to any crowd simulation. However, we made some minor modifications to simulate dense crowds. The basic objective was to make the influence of neighbors extremely local. The two changes we made to our force model keeping this in mind were

1. We reduced the field of view of every person from 180 degrees in front of him to 120 degrees.
2. We reduced the value of $R$, used to compute the major and minor axes of the elliptical region of influence around each person, to an extremely low value.

From an implementation perspective, we pre-divided the scene into partitions so that for any person $X$, to determine the people who will have an influence on him, we only need to consider other people in his own partition and in the neighboring partitions. This was extremely important to ensure that the simulation was fast enough.