UnrealScript Game Programming Cookbook

AI and Navigation

146

Now it's time to create our follow state. We're going to write the function for

FindNavMeshPath() first, which is nearly identical to the one we used in our

previous recipe. However, we are creating new constraints here. We're passing

in our target variable, which was defined previously in our idle state, as the pawn

our bot has just seen. We then tell the bot to find the most appropriate path to our

pawn by returning the NavigationHandle.FindPath function.

/*=======================================================

* Nav Mesh code for following our pan

======================================================*/

state Follow

{

ignoresSeePlayer;

functionboolFindNavMeshPath()

{

/** Clear cache and constraints (ignore recycling

for the moment) */

NavigationHandle.PathConstraintList = none;

NavigationHandle.PathGoalList = none;

// Create constraints

class'NavMeshPath_Toward'.static.TowardGoal

(NavigationHandle,target);

class'NavMeshGoal_At'.static.AtActor

(NavigationHandle, target,32);

// Find path to our pawn

return NavigationHandle.FindPath();

}

6. The second half of our follow state is where the state actually begins.
   If we can reach our pawn directly, then we just move toward it without needing to
   perform any sort of pathfinding. Otherwise, if the bot determines that it can't reach
   our pawn directly then it's time to perform pathfinding. The bot will now create a path
   to its target Actor.
   With the DrawPathCache() function, we draw lines to each point in our path
   cache, from our current location to where our bot is. Afterwards, we move to the first
   node on that path. The two lines of debug code that follow determine the color of our
   lines, as well as the color of the sphere at our next location.
   Once we've reached our pawn, go back to the beginning of the state again. If at any
   point we've determined that we can't reach the pawn, whether through pathfinding
   or not, we go back to our idle state to prevent an infinite loop, which would create a
   game crashing bug.