// NavMeshAgent helper function that returns the nearest valid point for a
// given destination. This is really useful for click & wsad movement
// because the player may click into all kinds of unwalkable paths:
//
// ________
// |xxxxxxx|
// |x| |x|
// P A|B| C |x|
// |x|___|x|
// |xxxxxxx|
//
// if a player is at position P and tries to go to:
// - A: the path is walkable, everything is fine
// - C: C is on a NavMesh, but we can't get there directly. CalcualatePath
// will return A as the last walkable point
// - B: B is not on a NavMesh, CalulatePath doesn't work here. We need to
// find the nearest point on a NavMesh first (might be A or C) and then
// calculate the nearest valid one (A)
public static Vector2 NearestValidDestination(this NavMeshAgent2D agent, Vector2 destination)
{
// can we calculate a path there? then return the closest valid point
NavMeshPath2D path = new NavMeshPath2D();
if (agent.CalculatePath(destination, path))
{
return(path.corners[path.corners.Length - 1]);
}
// otherwise find nearest navmesh position first. we use a radius of
// speed*2 which works fine. afterwards we find the closest valid point.
NavMeshHit hit;
if (NavMesh.SamplePosition(new Vector3(destination.x, 0, destination.y), out hit, agent.speed * 2, NavMesh.AllAreas))
{
Vector2 hitPosition2D = new Vector2(hit.position.x, hit.position.z);
if (agent.CalculatePath(hitPosition2D, path))
{
return(path.corners[path.corners.Length - 1]);
}
}
// nothing worked, don't go anywhere.
return(agent.transform.position);
}
void OnDrawGizmos()
{
// only while game is running, otherwise navmeshagent2d has no 3d agent.
if (Application.isPlaying)
{
// can't cache agent because reloading script sometimes clears cached
NavMeshAgent2D agent = GetComponent <NavMeshAgent2D>();
// get path
NavMeshPath2D path = agent.path;
// color depends on status
Color color = Color.white;
switch (path.status)
{
case NavMeshPathStatus.PathComplete: color = Color.white; break;
case NavMeshPathStatus.PathInvalid: color = Color.red; break;
case NavMeshPathStatus.PathPartial: color = Color.yellow; break;
}
// draw the path
for (int i = 1; i < path.corners.Length; ++i)
{
Debug.DrawLine(path.corners[i - 1], path.corners[i], color);
}
// draw velocity
Debug.DrawLine(transform.position, transform.position + (Vector3)agent.velocity, Color.blue, 0, false);
}
}
public bool CalculatePath(Vector2 targetPosition, NavMeshPath2D path)
{
var temp = new NavMeshPath();
if (agent.CalculatePath(NavMeshUtils2D.ProjectTo3D(targetPosition), temp))
{
// convert 3D to 2D
path.corners = temp.corners.Select(NavMeshUtils2D.ProjectTo2D).ToArray();
path.status = temp.status;
return(true);
}
return(false);
}
