  We present Topology-Guided ORCA as an alternative simulator to replace ORCA
for planning smooth multi-agent motions in environments with static obstacles.
Despite the impressive performance in simulating multi-agent crowd motion in
free space, ORCA encounters a significant challenge in navigating the agents
with the presence of static obstacles. ORCA ignores static obstacles until an
agent gets too close to an obstacle, and the agent will get stuck if the
obstacle intercepts an agent's path toward the goal. To address this challenge,
Topology-Guided ORCA constructs a graph to represent the topology of the
traversable region of the environment. We use a path planner to plan a path of
waypoints that connects each agent's start and goal positions. The waypoints
are used as a sequence of goals to guide ORCA. The experiments of crowd
simulation in constrained environments show that our method outperforms ORCA in
terms of generating smooth and natural motions of multiple agents in
constrained environments, which indicates great potential of Topology-Guided
ORCA for serving as an effective simulator for training constrained social
navigation policies.
