What is the most effective way to create a State Machine in Fusion 2.5?

Let me explain what I mean by a state machine.

I have an enemy. We'll call him Goblin.

Goblin does various things based on conditions, however it's almost quite messy when dealing with dozens of events. I want to know people's personal ways of approaching a system if they were to make Goblin do the following:

Code:

---

[Entity.alterableValue]

IF (Goblin.distanceFromPlayer) > 500
--Goblin.animation = idle

IF (Goblin.distanceFromPlayer) < 500 AND (Goblin.distanceFromPlayer) > 200
--Goblin.animation = running
--Goblin moves toward player

IF (Goblin.distanceFromPlayer) = 200
--Goblin.animation = rangedAttack
--Goblin launches dagger object

IF (Goblin.distanceFromPlayer) < 200
--Goblin.animation = scared
--Goblin moves away from player

---

This is a pure example. I have tried many different ways and this seems to be the most effective however it is not without flaws.
Let's take a look at what I am trying to achieve.

If the player is farther than 500px the Goblin stands still.
If the player is closer than 500px but farther than 200px, the Goblin approaches the player.
If the player is exactly 200px away the Goblin will throw a knife, and stop moving.
If the player is closer than 200px the Goblin will run away to protect himself.

The issue I face is that none of these seem to work. The (hypothetical) Goblin would always get mixed up. Sometimes he'd run, other times he'd be clueless as to what he should do.

I desperately need a suggestion of how to better tackle this simple kind of AI, in a way that states are generated out of what the Entity was doing before the last event was triggered, in a nice and clean way that can be applied to large numbers of conditions and variables. Clearly this is ineffective and there are too many loose ends for the AI to become stable.

Firstly: unless your goblin is only moving a pixel at a time, comparing his position to an exact value (200 in your case) is a bad idea, since he could very easily skip over that value if moving at higher increments. A better idea is to check within a range of at least his width or a little smaller. Secondly, you need some Lower/Greater or equal to signs, instead of something like "< 500 and > 200"; 500 and 200 will be counted as "void" zones where nothing happens, and only 499/501 and 199/201 and beyond will be counted. Doing "<= 500 and > 200" is better.

Give me a few minutes and I might be able to throw an example together for you. Alterable values will most likely be your safest bet.

OK.

Here i'm taking advantage of groups and the way Fusion reads events (top to bottom). First, the state number is determined using your distances. Then, the correct state group is activated. Each group is deactivated after all of its actions have been read (putting close group at the bottom is important here) so Fusion has to manually open it again. This stops multiple state groups being open and having their actions read when they shouldn't be.

Very simple example that only uses left and right directions, but you should be able to go from here. Attachment 18840 (you might want to make the frame bigger or lower the idle distance value since it's high, but the Idle state still works)

Thanks so much! In your example, where have you specified where the arrow should be launched, and the limitation of 1 arrow per second in the required state?

I used a value called "arrow cooldown" in the goblin himself (I assume you know where Alterable Values are found. But if you don't, they're in the Object properties sidebar when you click on an object). When it's at 0, an arrow is fired and it is reset to some arbitrary value (I used 35). Then you just constantly count that value down.

I used the direct distance between the player and the goblin (x of player - x of goblin) and then capped it to either -1 or 1 using the Range(value, minimum, maximum) function to set the arrow's direction. Using that version of distance gets the delta of the two positions, so if the goblin is lower than the player the value returned will be negative and vice versa. To actually make the arrow move towards the direction, I set it's position to x ("arrow") + (speed value * arrow direction). Since the direction is either -1 or 1, the speed will be multiplied and adjust appropriately.


EDIT: If you wanted to know the specific line for launching the arrow and setting the delay, it's 36. 61 counts the cooldown value to 0.

Hello Exorian,

I think States Machines are easily implementable. I routinely do them myself. To start off, the below image is a general flowchart of what will be happening.
https://dl.dropboxusercontent.com/u/...012%202016.png

1. Determine the State
   
   • Naturally you need to be able to determine what the object's current state should be. This is where you would do all your position testing.
   • Example: If <Distance between Goblin and Player is exactly 200>, then Set GoblieState to "RangedAttack"
   
   
2. State Cooldown
   
   • This is used to put in some downtown between a new state and any actions for the state. Suppose after a Goblin is assigned the RangedAttack state, he waits to throw a knife after 0, 5, and 10 seconds. You would code these cooldowns in this section
   
   
3. State Action
   
   • If a state has an action, this is where you would put the actions. As an example, in the RangedAttack state you would tell the Goblin to throw the knife towards the player here
   
   
4. Action Cooldown
   
   • If you want to put some sort of cooldown between the action and the Goblin's next state, you would do that here. Some states have need a cooldown while others may not. If you code with this action cooldown in mind, you can easily change your mechanic as needed
   • As an example, imagine if the player and the Goblin are exactly 200 pixels apart and the Goblin will always throw a knife immediately when it is assigned the Ranged Attack State. If the player doesn't move and the goblin doesn't move, the goblin will be throwing a knife every frame!

Personally, I prefer something like the following flowchart:
https://dl.dropboxusercontent.com/u/...%20%282%29.png
In this flowchart, the yellow boxes are a decision; you choose one of them. With this flowchart, you can have one state go directly another state. For example, you could have it such that the RangedAttack state will always go to the scared state.

Hopefully offers a new way for you to tackle state machines.

Quote:

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Originally Posted by casleziro

I used a value called "arrow cooldown" in the goblin himself (I assume you know where Alterable Values are found. But if you don't, they're in the Object properties sidebar when you click on an object). When it's at 0, an arrow is fired and it is reset to some arbitrary value (I used 35). Then you just constantly count that value down.

I used the direct distance between the player and the goblin (x of player - x of goblin) and then capped it to either -1 or 1 using the Range(value, minimum, maximum) function to set the arrow's direction. Using that version of distance gets the delta of the two positions, so if the goblin is lower than the player the value returned will be negative and vice versa. To actually make the arrow move towards the direction, I set it's position to x ("arrow") + (speed value * arrow direction). Since the direction is either -1 or 1, the speed will be multiplied and adjust appropriately.


EDIT: If you wanted to know the specific line for launching the arrow and setting the delay, it's 36. 61 counts the cooldown value to 0.

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I think I'm severely missing something here. I've gone through all of your events and I can't see one line that specifies to "launch an arrow" anywhere. :s

Edit: I see, you were using groups. I've never used them before. Sorry.

I think the key here is the way of thinking.
If i remember correctly a key point in a state machine is that only 1 state is active at any given time.

So Goblin will have X number of states, example:

State 1 = Goblin behaves according to a specific logic/ in a specific manner
State 2 = Goblin behaves according to another specific logic/ in a specific manner
State 3 = Goblin behaves according to another specific logic/ in a specific manner
etc
^ The specific behavioiurs of the Goblin only work within its active state.

So one could start off by creating the different states ( idle, roaming, attacking etc ) seperatly, and when done simply click the states together by correctly 'transitioning' between them accordingly ( based on specific conditions ).

Quote:

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Originally Posted by casleziro

OK.

Here i'm taking advantage of groups and the way Fusion reads events (top to bottom). First, the state number is determined using your distances. Then, the correct state group is activated. Each group is deactivated after all of its actions have been read (putting close group at the bottom is important here) so Fusion has to manually open it again. This stops multiple state groups being open and having their actions read when they shouldn't be.

Very simple example that only uses left and right directions, but you should be able to go from here. Attachment 18840 (you might want to make the frame bigger or lower the idle distance value since it's high, but the Idle state still works)

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Please help! I've done everything exactly the same up until line 39, but for some reason an arrow is drawn on the enemy immediately when I run the app, thus in 'state 0 idle'. And when it should go to state 2 it doesn't do anything. Sorry if I'm missing something, but I've only been using Fusion for a week or so... . Attachment 22310

[Edit] Found the problem myself. Didn't know about the 'Activate when frame starts' checkbox when making a group events.

Quote:

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Originally Posted by casleziro

OK.

Here i'm taking advantage of groups and the way Fusion reads events (top to bottom). First, the state number is determined using your distances. Then, the correct state group is activated. Each group is deactivated after all of its actions have been read (putting close group at the bottom is important here) so Fusion has to manually open it again. This stops multiple state groups being open and having their actions read when they shouldn't be.

Very simple example that only uses left and right directions, but you should be able to go from here. Attachment 18840 (you might want to make the frame bigger or lower the idle distance value since it's high, but the Idle state still works)

---

Hi casleziro. I've made my own thread asking this question but I'll pose it to you here too: how would you go about something like this if there were two or more goblins? Since the code is only read top to bottom once per frame, only the goblins that share a state with the highest priority goblin will do anything - the code for the other states will never run. One solution is to loop through the enemies and activate/deactivate groups according to each enemy, but this requires putting the "On loop" line at the top of every single event in the enemy code, which is hardly elegant. The only decent option I've found so far is to use behaviours, but I've heard they're so problematic they're best avoided entirely.

So this is the challenge I'm facing - to create a state machine that handles multiple instances without having every single line start with "On loop..." or "State of [object] = ...".