How to increase vertical Nav Mesh detection for AI Actors?

Development Programming & Scripting AI
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1

For swimming AI, I wish to use a Nav Mesh, so they can avoid obstacles and swim up and down - preferably.
I figured I should try to solve this with a Nav Mesh, since UE4 has kindly implemented it.

To avoid having the fishes stick to the “ground” of the map, I would have to increase the Query Extent, which is testable with a Navigation Testing Actor (see images below).

So what I did:

  • Add Nav Mesh Bounds volume
  • Add AI actor with Character Movement Component
  • Increase Default Query Extent in Project Settings (Engine > Navigation System)
  • No Profit?

Increasing the Default Query Extent, under Agents, increases it along the positive and negative z-axis, which is unfortunate, since I would like the enemy fishes to prioritize the bottom Nav Mesh surface.

I have attached two screenshots showcasing the “bad” behaviour, which I would like to circumvent.

The blue Bounding Box, showcases the Extent, which is scaled in both directions, vertically. Preferably, I would like to move it down, relative to the Nav Agent.

200342-example1.png
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To hit the point home, here is what happens when the enemy swims underneath some platform:

200343-example2.png
200343-example2.png1025×532 227 KB

So my question to you good people is: how would I lower the Nav Mesh detection, without increasing the actor size, or something rather silly. Is there a clean way of having the “Enemy Fish” ignore the top platform as much as possible, without using a Nav Modifier Volume ?

2

I think what you are looking for is to implement some BP for when the fish detects a certain actor (platform) they react or move a certain way. Maybe use Actor Begin overlap?

3

So you suggest creating my own pathfinding for the swimming AI? Is there a good reference somewhere? I haven’t been able to find anything related to Swimming AI in UE4.

4

I assume you have an AI behavior tree. You can implement some kind of sight check, and have them move to a waypoint. Detect it however you like, break the result cast to the object types you want it to avoid or whatever (maybe check some variables), Maybe add a line trace if nothing blocks their view (so they properly see it) and then have that character call it’s response action to that particular object.

5

Maybe you could also look into splines? I’m not sure what your game is about and how your AI needs to move.

6

It says so in the OP: The AI is swimming, a fish to be exact. The game is played sidescrolled and the obstacles are props of a sunk ship, meaning the pathfinding may get too complex to do in just blueprint, which is why I was hoping someone could suggest a solution for the Query Extent issue.