Jump to content

GameStates with CStateManager

Averice

1,209 views

I released an OOP class sytem for leadwerks last time this time I'm going to post my StateManager class which I use to control all the gamestates for the game I am working on.

 

If you don't know what a Statemanager is or what my interpretation of one is I'll run through it quickly.

Generally speaking it's just a stack full of 'states' each state has a list of functions with identical names but different internal functionality, the game will call these functions but ONLY for the active state, say your game has a Draw function but you want a splash screen with a Draw function, you'll separate these into different States for the stack, now when your splash state is active only the splash's Draw function will be called. State stacks almost always run [L]ast n [F]irst [O]ut, so the last state you push onto the stack will be the one the game starts using, so to have a splash screen -> menu -> game order in your stack you would push the game onto the stack first, the menu second and the splash last so that the splash is the first thing the end user sees.

 

Enough ramblings let me post some code.

 

statemanager.lua

requires the class scripts.

class "CStateManager";

function CStateManager:Init()
self.States = {}
end

function CStateManager:Push(state, init)
if( ctype(state) == "CState" ) then
self.States[#self.States+1] = state;
if( init ) then
if( self.States[#self.States-1] and self.States[#self.States-1].isinit ) then
self.States[#self.States-1]:Shutdown();
self.States[#self.States-1].isinit = false;
end
self.States[#self.States]:Init(App.context);
self.States[#self.States].isinit = true;
end
else
print("StateManager: CStateManager.Push expected CState got: "..ctype(state));
end
end

function CStateManager:InitCurrentState()
if( self.States[1] and not self.States[#self.States].isinit ) then
self.States[#self.States]:Init(App.context);
self.States[#self.States].isinit = true;
end
end

function CStateManager:Pop()
if( self.States[1] ) then
if( self.States[#self.States].isinit ) then
self.States[#self.States].isinit = false;
self.States[#self.States]:Shutdown();
end
local oldState = self.States[#self.States];
self.States[#self.States] = nil;
self:InitCurrentState();
return oldState;
end
print("StateManager: Called CStateManager.Pop with empty stack");
end

function CStateManager:GetAll()
return self.States
end

function CStateManager:GetActive()
if( self.States[1] and self.States[#self.States].isinit ) then
return self.States[#self.States];
end
print("StateManager: Called CStateManager.GetActive with no running states");
end

function CStateManager:Pause(state)
if( ctype(state) == "CState" ) then
state.paused = true;
end
end

function CStateManager:Resume(state)
if( ctype(state) == "CState" ) then
state.paused = false;
end
end

function CStateManager:IsPaused(state)
if( ctype(state) == "CState" ) then
return state.paused;
end
end

function CStateManager:Call(func, ...)
if( self.States[1] and self.States[#self.States].isinit and not self.States[#self.States].paused ) then
if( self.States[#self.States][func] ) then
self.States[#self.States][func](self.States[#self.States], ...);
end
end
end

 

state.lua

-- Tiny file this one. really just a declaration and a nilfix file.

class "CState";

function CState:Init()
end

function CState:Shutdown()
end

 

Example useage.


-- Our splash screen.
SplashScreen = new "CState"

function SplashScreen:Init()
self.Something = "HELLO";
end

function SplashScreen:Think()
self.Something = self.Something.."O";
end
function SplashScreen:Draw()
App.context:DrawText(self.Something, 100, 100);
end

-- Now something else.
Random = new "CState"

function Random:Draw()
App.context:DrawText("Second State", 100, 200);
end

 

-- Now in our main file to initialize out statemanager and load our states.

function App:Start()
StateManager = new "CStateManager";
StateManager:Push(Random); -- Remember this goes before the splash so we see it AFTER the splash
StateManager:Push(SplashScreen, true); the true means we want to initialize this, as it's the last state being pushed we may aswell tell the statemanager we are ready to begin.
end

function App:Loop()
StateManager:Call("Think") -- Can name your functions anything, Init and Shutdown are always the same though.
StateManager:Call("Draw", "some", "arguments", "here", "if", "you", "want");
end

 

To remove the current state from the stack and initialize the next, we use StateManager:Pop();

I hope people get some use out of this, and I hope I've explained it nice enough.



2 Comments


Recommended Comments

Instead of:

 

SplashScreen = new "CState"

 

wouldn't you want:

 

class "SplashScreen" : extends "CState"

 

since that's sort of the point to why you made the extends function? Just curious why you didn't go that route?

 

Also I notice you are a semicolon guy. They aren't needed when each statement is on a separate line, but guessing you come from C++ and just a habit or you have some plans for them?

Share this comment


Link to comment

SplashScreen is an instance of CState not a new derivative class, I know semi colons aren't needed just a habit that I don't see the need in breaking.

 

I try to make these modules self contained, so any errors are reported to the user instead of crashing the game, CStateManager checks if a CState is being pushed onto the stack, if it's not a CState it isn't allowed. The inheritance in my class module is used to have base classes with inherited values, whereas the SplashScreen in this example is just a class instance with modified public methods ( I know they're all public being Lua since we can't privatize them without a workaround with the standard class metatable )

 

It would still work extending instead of instancing but most states will not be even remotely similar so inheriting values we won't use wouldn't be wise.

Share this comment


Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Add a comment...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Blog Entries

    • By Josh in Josh's Dev Blog 5
      You might have seen this graphic comparing the size of the world in different games. I've played Fuel, and never reached the end of the world in that game. You can drive for a very long time on those roads.

      We want to use the new engine for realistic simulations of air and ground movements. At normal cruising altitude of a commercial airliner, the pilot has a view range of about 400 kilometers. The image below shows that area (800 x 800 km). You can see the areas of the biggest games ever fit neatly into the corner of just our visible area.

      The gray space above is not the total world size, it is just the area you can see at once from high altitude. The total world size is about 50 times bigger.
      This is what I am working on now.
    • By Josh in Josh's Dev Blog 26
      Gamers have always been fascinated with the idea of endless areas to roam.  It seems we are always artificially constrained within a small area to play in, and the possibility of an entire world outside those bounds is tantalizing.  The game FUEL captured this idea by presenting the player with an enormous world that took hours to drive across:
      In the past, I always implemented terrain with one big heightmap texture, which had a fixed size like 1024x1024, 2048x2048, etc.  However, our vegetation system, featured in the book Game Engine Gems 3, required a different approach.  There was far too many instances of grass, trees, and rocks to store them all in memory, and I wanted to do something really radical.  The solution was to create an algorithm that could instantly calculate all the vegetation instances in a given area.  The algorithm would always produce the same result, but the actual data would never be saved, it was just retrieved in the area where you needed it, when you needed it.  So with a few modifications, our vegetation system is already set up to generate infinite instances far into the distance.

      However, terrain is problematic.  Just because an area is too far away to see doesn't mean it should stop existing.  If we don't store the terrain in memory then how do we prevent far away objects from falling into the ground?  I don't like the idea of disabling far away physics because it makes things very complex for the end user.  There are definitely some tricks we can add like not updating far away AI agents, but I want everything to just work by default, to the best of my ability.
      It was during the development of the vegetation system that I realized the MISSING PIECE to this puzzle.  The secret is in the way collision works with vegetation.  When any object moves all the collidable vegetation instances around it are retrieved and collision is performed on this fetched data.  We can do the exact same thing with terrain   Imagine a log rolling across the terrain.  We could use an algorithm to generate all the triangles it potentially could collide with, like in the image below.

      You can probably imagine how it would be easy to lay out an infinite grid of flat squares around the player, wherever he is standing in the world.

      What if we only save heightmap data for the squares the user modifies in the editor?  They can't possibly modify the entire universe, so let's just save their changes and make the default terrain flat.  It won't be very interesting, but it will work, right?
      What if instead of being flat by default, there was a function we had that would procedurally calculate the terrain height at any point?  The input would be the XZ position in the world and the output would be a heightmap value.

      If we used this, then we would have an entire procedurally generated terrain combined with parts that the developer modifies by hand with the terrain tools.  Only the hand-modified parts would have to be saved to a series of files that could be named "mapname_x_x.patch", i.e. "magickingdom_54_72.patch".  These patches could be loaded from disk as needed, and deleted from memory when no longer in use.
      The real magic would be in developing an algorithm that could quickly generate a height value given an XZ position.  A random seed could be introduced to allow us to create an endless variety of procedural landscapes to explore.  Perhaps a large brush could even be used to assign characteristics to an entire region like "mountainy", "plains", etc.
      The possibilities of what we can do in Leadwerks Engine 5 are intriguing.  Granted I don't have all the answers right now, but implementing a system like this would be a major step forward that unlocks an enormous world to explore.  What do you think?

    • By Haydenmango in Snowboarding Development Blog 6
      So I've been researching snowboarding lately to get an idea of what animations and mechanics I need to create for my game.  I have learned lots of interesting things since I've only seen snow once or twice in my entire life and have never even tried snowboarding or any other board sports (skateboarding, surfing, etc.) for that matter.
       
      Snowboarding tricks are quite interesting as they are mostly derived from skateboarding.  Snowboarding tricks pay homage to their equivalent skating tricks by sharing many concepts and names.  For example basic grabs in snowboarding share the same concepts and names as skateboarding: indy, mute, method, stalefish, nosegrab, and tailgrab.  Something interesting to note is in snowboarding you can grab Tindy or Tailfish but this is considered poor form since these grabs can't be done on a skateboard (due to the board not being attached to the skaters feet) and grabbing these areas is generally something a novice snowboarder does when failing or "half-assing" a normal grab.  Check out this diagram to see how grabs work -
       
       
      So, after reading lots of text descriptions for tricks I was still confused by what all these terms meant and how they were actually applied.  So my next step was to look up these tricks actually being done and I found some really cool videos showing off how to do various tricks.  This video in particular is the best reference material I've found as it contains nearly every trick back to back with labeled names and some tweaks -
       
      Sadly my rigged model doesn't handle leg animations with the snowboard that well so I can't animate as many tricks as I want to.  Regardless there will still be around 15 total grab/air tricks in the game.  Now it's time for me to stop procrastinating and start animating!  
×
×
  • Create New...