Optimizing Many-Unit Interactions

[hoary mason]

I have a game with many units which all follow a series of behavior patterns. They should change their current behavior or behavior pattern depending on certain conditions, almost all of which have to do with their proximity to certain triggers. For example, a Scout should return to the Colony when it comes within range of whatever it is scouting for (eg, food). An Attendant should increase the progress on hatching an egg when it is close enough to the Queen. What is the best way to manage this system? Currently, I'm using OnCollisionEnter and OnCollisionStay to drive behavior changes, but the physics of it all is pretty unnecessary for my game, and I'm worried all the collision logic is slowing things down. Is detecting GameObjects within a radius cheaper? Is it feasible to have GameObjects inform other GameObjects of their proximity somehow?

I'm at the stage of my game where I need to land on a more permanent solution to unit behavior and physics. I don't need faithful physics, esp gravity. I mostly need my units to stay inside the world, avoid clipping through each other too much if possible (not really that important except for polish), and to detect whether they're within range of "food" or "another unit" or "the colony" etc.

[fathom carbon]

well, you detect game objects within a radius by using physics queries!

[hoary mason]

That makes sense.

[fathom carbon]

physics are a very efficient way to detect what things are near you

[hoary mason]

I got up to ~100 units last night and I think performance tanked -.-

[fathom carbon]

you don't have to compare every object's position to every other object's position; there are some optimizations in there

[clear parrot]

You can detect distance with simple Vector math. no physics system needed

[hoary mason]

incl OnCollision?

[hoary mason]

Yes, but it surely can't be too efficient to be tracking the distance between every unit and every other unit?

[fathom carbon]

i would probably go with overlap queries that only fire every now and then

[hoary mason]

Or else you have to track when units enter and exit a radius or other units?

[fathom carbon]

and have a layer dedicated to things you'd want to detect

[hoary mason]

as opposed to every frame?

[fathom carbon]

yeah

[hoary mason]

Layers are beyond me, but that'll be my next research topic, I suppose

[clear parrot]

It would be more efficient than doing the same with collision detection.

[fathom carbon]

now, I think it's also reasonable to just do some distance calculations if you have a small set of things you're looking for

[hoary mason]

yeah, this feels true to me

[fathom carbon]

and you can always profile it to see which one works out better

[hoary mason]

true

part of me wonders if i would have been better off making the game 2D from the start. is that more efficient?

that's a dumb question, it must be lol

[clear parrot]

The rub is that if you want your units to avoid eachother "Not Clip through eachother" you'll need some sort of path finding, and distance alone wont get you there

[fathom carbon]

You should definitely be using triggers, rather than colliders

triggers are simpler: they don't do any actual physical interactions

[hoary mason]

currently the "default" behavior for a unit is to pick a random rotation between -2.5 and 2.5 degrees and move forward by it's "speed". if it detects another unit inside its radius, couldn't it avoid it that way?

[hoary mason]

Layers and Triggers. I figured I'd have to learn them eventually. lol

[clear parrot]

In this implementation they could both go the same way, and if they have to resolve this before they keep moving, then they could get stuck. Unity's pathfinding is pretty robust, and easy to use. I'd say have a look at it.

[hoary mason]

and a little clipping is fine, but I do want them to behave as though they know other units exist

[hoary mason]

how do you square what is essentially brownian motion with pathfinding? when a unit is too close, pathfind away and then resume brownian motion?

i want them to behave like ants if you couldn't tell lol

(they are ants)

[clear parrot]

I dunno. I've never tried to roll my own pathfinding. Unity has always done the trick

[hoary mason]

is there an easy to ditch all colliders but prevent units from falling through the floor? just be careful with their transform.position.y?

[fathom carbon]

I guess you could use nav mesh agents

They stick to the surface they’re on

[hoary mason]

and then triggers for proximity?