UnityLearn – AI For Beginners – Crowd Simulations – Fleeing – Steven Lilley

May 22, 2020

AI For Beginners

Crowd Simulations

Part 2

Beginner Programming: Unity Game Dev Courses

Intro

I was going to combine both of the end parts of the Crowd Simulation tutorial into one blog, but the Flocking tutorial was rather large and interesting so I decided to break it off into its own post. Because of that, this is a smaller one just focused on the basic fleeing crowd logic.

Fleeing

This is similar to the concept covered with single AI agents, it is just being applied to many agents here. An object is introduced to the environment and the fleeing agents determine the vector towards that object, and set a new course for the exact opposite of that vector.

Key Parameters covered for their flee inducing object:
Radius of Influence – how close agents must be to be affected by the object
Cooldown – how long an agent flees before returning to standard behavior

They decided to induce fleeing by adding a cylinder object to the Nav Mesh environment by clicking. This required adding a mouse button script along with adding a dynamic obstacle to the Nav Mesh again (similar to the FPS controller from the last tutorial).

This tutorial gets into several useful NavMesh methods that have not been used yet. These are helpful references to use when expanding and developing my own pathfinding methods, since they show some useful options to give developers when working with intelligent pathfinding.

There are NavMeshPath objects which hold information about a path for the agent to some given destination. You can set these path objects using the CalculatePath method, using a vector3 position (the destination) and the NavMeshPath object as parameters to set that path with that given destination. This alone does NOT set the agent along this path, it simply gets the information for that path (this is useful for the next step).

They perform a check on the path using fields within the NavMeshPath class and an enum named NavMeshPathStatus before actually setting the new destination of the agent. The check is as follows:

NavMeshPath path = new NavMeshPath();
agent.CalculatePath(newGoal, path);

if(path.status != NavMeshPathStatus.PathInvalid){… }

You are able to access the status of a NavMeshPath with a field within the class. They use this to check that the status of the newly created path is valid by checking it against the PathInvalid option within the NavMeshPathStatus enum. Only after passing this check do they set the newly determined path of the agent. Here, they also show that NavMeshPath has a vector3 array field named corners, which are effectively the waypoints of the path the agent uses for its pathfinding.

Summary

This fleeing logic was pretty basic, but it was helpful to learn a bit more about Nav Mesh in general for Unity. The extra information about NavMeshPath was good to learn about, as well as giving me more options on useful aspects to give my own pathfinding systems.