So for the past couple of months I’ve been working on a new fighting game prototype. After discovering TrueSync by Exit Games, I’ve been trying very hard to create a new fighting game with it. Again, one of my biggest regrets with Battle High is that I was never able to implement multiplayer before its release. I definitely feel that TrueSync could definitely help me achieve that! Anyway, I decided to write a little bit about the game and what I’m trying to do with it.
I chose this name because what I made was a prototype, and I wanted to make this clear. I decided to use only assets from the Unity3D Asset Store, which TrueSync already is. This includes my characters, audio, and more! Here is a short list of some of the assets I am using:
I had several goals while making this prototype.
Learn TrueSync With a Focus on a Fighting Game
My first goal was to learn TrueSync and make a game using it. I think I accomplished this. In fact, it’s not my first TrueSync experiment. Diamonds Not Donuts, a small game I released on itch.io for free, is! That being said, for ProtoFighter, I wanted to focus more on fighting games and various issues concerning them. ProtoFighter has a lot of gameplay functionality that most fighters do — blocking, jumping, attacking, special moves, supers, rounds, etc. Obviously it’s missing a lot to be a complete fighting game package — single player modes, balance is a MESS, more characters, etc. Again, for a pre-pre-pre alpha, I think I achieved my goal, but of course, when it comes to TrueSync, there are still a ton of questions I have and hope to continue to answer them as I expand upon this prototype.
Make a Fighter That Is Slightly More Accessible Than Most
Though not TrueSync related, I’ve always wanted to try and make a fighting game that was a bit more accessible to the average player. Maybe not as extreme as Fantasy Strike, but something that I could still explain relatively easily.
In ProtoFighter, though I sadly haven’t released a tutorial yet, I tried to do this. Essentially, instead of performing quarter circle attacks, I simplify this to forward or back plus an attack. Now, a lot of people would immediately say this oversimplification could cause issues such as instant dragon punches or anti-airs, so to solve this I did two things. Firstly, all initial moves such as forward+punch have rather long start-up and are reserved for moves like overheads or projectiles. Then, every special move has a “secondary” special that branches from it. For example, forward+punch may begin an overhead but then pressing up before the attack activates, a secondary attack, probably an anti-air attack, would be performed. The hope is that performing the initial move and then the secondary move will require just enough time and frames that the anti-air move won’t be so instantaneous. Maybe this won’t help, but the idea it’s simple to actually perform an attack, but requires some dexterity and memorization to cancel one move into another properly.
A secondary idea I then had is to still allow players to perform attacks using quarter-circles; however, these players would be rewarded with a slight meter bonus, so you don’t have to perform moves properly to compete or play, but players who can are rewarded slightly for taking the time and effort to perform more complex inputs. I can’t really tell if this input system will be good or not until someone tests it, which is why I released the prototype.
Create a Framework
My third goal was to begin creating a framework so that I can create future titles, TrueSync or not, more quickly. A lot of games I work on are usually fighting game influenced, so I wanted to construct a framework so that creating future titles, whether 2D or 3D, would be easier in the future. Though not perfect, I definitely tried to abstract more of my classes and functionality and believe I could quickly go from this 2.5D fighting game to a 3D game rather quickly with few changes.
So, for this fighting game, I learned a good amount about TrueSync. TrueSync attempts to be deterministic, allowing a local player’s inputs to be immediately respected, passed over the network, and compared to the game’s state and rolled back if there are inconsistencies found and resimulated.
The issue though is that Unity3D wasn’t built to be deterministic. Its use of floats and random system for example can cause various issues. It’s animation system also isn’t deterministic so trying to perfectly simulate results across two machines can be rather problematic. Anyway, here are some tips I found were helpful for completing my prototype.
Note, these tips were written for Unity3D version 2017.1.1f1 and TrueSync version 1.1.0B.
Don’t “Press” Inputs
TrueSync uses a unique method to capture and send input, it’s called OnSyncedInput. Here’s an example of how it works.
public class MyTSClass : TrueSyncBehaviour
public override void OnSyncedInput()
So in the above, TrueSyncInput is used to pass inputs over the network. The first argument is a byte, used as a key. I’m just using 0 for now, but if you use multiple, you should probably assign them to a constant. Then, I’m using Input.GetKeyDown to send a bool if space is down or not. One issue with this method is that it is performed similarly to OnFixedUpdate so calls such as “Input.GetKeyDown” don’t work consistently as when OnSyncedInput is called, Input.GetKeyDown is sometimes missed. To resolve this for button inputs, here’s what I did:
public class MyTSClass : TrueSyncBehaviour
bool hasPressed = false;
public override void OnSyncedInput()
bool singlePress = false;
hasPressed = true;
singlePress = true;
else if (hasPressed)
hasPressed = false;
This change uses a bool that is set to true when OnSyncedInput is executed if the space bar is currently down. The toggle is then reset once the spacebar is no longer being held down. The bool that is actually pased in TrueSyncInput.SetBool is only set if the keyboard is down AND hasPressed was false before being set to true. This way, the first entry of TrueSyncInput will be true for only one execution of OnSyncedInput. This should prevent any issues with OnSyncedInput missing an input as the average button press usually occurs for a few frames. I don’t use this method exactly in ProtoFighter, but the idea is similar. Instead of doing separate Booleans for each input type — up, down, left, right, etc. — I use an integer and bitmasking to change it during OnSyncedInput.
Treat TrueSync Like A Separate Engine
This sounds silly as Unity3D is a game engine; however, to make TrueSync’s determinism work properly, you have to use a lot of unique structs and classes that it introduces. There’s FP, or FixedPoint, for float values for example and TSVector for Vector3’s. Also, TrueSync has its own Transform class (TSTransform) that does not have all the functionality — at least now — that Unity3D’s Transform class has. You can’t use children the same way and certain methods such as those that convert transform information from world to local space are missing. Overall, you can’t just take a finished game and integrate TrueSync into it quickly.
One trick I had to do, for example, was figure out a way to align character hit spheres to certain joints. In a normal setting, I could just use the following:
Animator anim = GetComponent<Animator>();
Transform t = anim.GetBoneTransform(HumanBodyBones.Chest);
Vector3 chestPos = t.position;
However, one problem is that this creates a Vector3 and even though I can convert the position to TrueSync’s Vector3 equivalent, a TSVector, they may be different values between the multiple players due to floating point precision errors.
To resolve this, I built a tool to cycle through my animations and store important point information as a TSVector in a ScriptableObject. I don’t save the position though; instead, I save the vector from the center to this point. So, to get where the chest would be in my animation, it would be something like the following:
TSVector localChestVector = GetChestPosition(frame);
TSVector worldChestVector = tsTransform.position + tsTransform.rotation * localChestVector;
So, in the above, I’ve gotten a local vector for my chest position and then used the position of my player and rotation to define the world position for my chest now. You’ll also notice that I’ve used a frame. This is because a lot of fighting game interpret things as frames, and I believe interpreting your deterministic game in TrueSync is a lot easier to understand through the concept of frames than through time. Even though my 3D animation is made up of curves, I store different bone information in these TSVectors so they can be referred to later regardless of the rotation or position of my character. I also do a similar technique for moving a character by their root animation without actually having the Animator drive it.
No Animators — At Least How You Think
As of right now, TrueSync doesn’t have an Animator class. For fighting games, this can be an issue since animations and the accuracy of said animations is so important. To handle this, I did the following:
- Stored all of my animator data in a separate data structure, mostly just my transition parameters and conditions
- Muted ALL of my animation transitions
- Disabled the Animator Component
- Use Animator.Update(float)
So, even though the animator is disabled, Animator.Update(float) still allows the Animator to be updated. Even though you do have to use a float instead of an FP, the amount I update is determined by the frame I’m supposed to be on, so my update function looks like this.
private void Update()
anim.Update(((TrueSyncManager.DeltaTime) * syncedFrame - localFrame).AsFloat());
localFrame = syncedFrame;
So, here I have syncedFrame which is the frame of my animation that is set during OnSyncedUpdate. Then I substract the syncedFrame to the localFrame and convert it to a float value. I then set the localFrame to the syncedFrame. I used FP instead of integers in case I want to play the game in slow motion. This still needs some tweaking, however, but it gets the general idea across.
Overall, using Animator.Update(float) is great because it allows me to still get a lot of the functionality of Animators
- Transition blending
- Humanoid rigs
But with more control. This is one reason all transitions in the Animator are muted actually. Because I don’t want transitions to happen automatically and switch states suddenly if there is rollback. Doing it more manually allows me to switch state when I need to.
Just one small part of my AnimatorController; the red arrows show that my transitions are muted.
Anyway, the future of ProtoFighter is uncertain. I will most certainly not release this as a full game, but instead a fighting game demo. I know in this current 2D version I’d like to do the following:
- Add rooms and lobbies instead of the “Ranked Match” system it uses now
- Add stage select
- Add an interactive tutorial
- Balance and clean up the existing characters, Protolightning and Protaqua
- Start looking into AI and single player modes
Overall, the goal with this game is to eventually get a framework to a place where I can experiment with a variety of gameplay styles and making something myself later down the road, hopefully sooner rather than later. Maybe I can even use this to integrate TrueSync into Battle High 2 A+ — though I make zero promises.
ProtoFighter is available on itch.io & Game Jolt for free! If you download the game and play them, I’d love to hear your feedback — but make sure you try the multiplayer as that’s the main area I’m trying to focus on. Also, if you have any questions on TrueSync, I’d love to try and help as I think it’s a great asset and can help give online functionality to a lot of new indie game content — fighting games and other — in the future.