I'm developing a 2d fighting game in c++ (for learning purposes) and I'm having a hard time figuring out how to properly implement game logic. For a quick overview of my current architecture, I have component classes that act as data holders and I have 'systems' which are just functions designed to act on those components. I have a scene class which holds an array of fighters that are currently in game and this scene is passed to individual sub-systems which then can freely act on fighter components, updating fighters state:
//Add a fighter object to array of fighters and set starting position
scene.CreatePlayerFighter(160.0f, 0.0f);
scene.CreateAIFighter(80.0f, 45.0f);
gameWolrd.Init(scene);
Renderer.Init(scene, window);
AI.Init(scene);
//etc...
//Game loop
while (true)
{
Input.Update(scene);
Physics.Update(scene);
AI.Update(scene);
//etc....
window.ClearBuffers();
Renderer.Update(scene, colorShaderProgram);
window.SwapBuffers();
}
Again, inside each sub-system (Renderer, AI, Input, etc.) all fighter components are being passed into system functions and spit back out with new values which are then inserted back into fighters:
void Physics::Update(Scene& scene)
{
for (Fighter& fighter : scene.fighters)
{
//Update fighter position based on fighter's current velocity which has been set by input
TransformComponent newFighterPosition = System::MoveFighter(fighter.GetComponent<TransformComponent>(), fighter.GetComponent<VelocityComponent>());
//Insert new TransformComponent to update fighter's position
fighter.Insert<TransformComponent>(newFighterPosition);
}
}
This current architecture has the advantage of being loosley coupled in that I can add and remove systems very easily without effecting the fighter class or it's components directly. The problem is everything is hopelessly serial, as my scene is passed into each sub-system one by one to update fighters. I mention this problem because one of my thoughts to implement a game logic layer was to have higher level classes just call specific game engine system functions directly like physics.MoveFighter(TransformComponent, VelocityComponent, float amountToMove); where I can add additional parameters to give the user at the game logic layer level more control. Of course doing things this way means system functions would be called and invoked in any order the user of the game logic saw fit. Would there be a way to still implement a game logic layer in this way and maybe queue up all calls and reorder them to run correctly within the game engine? Or would there be a better way to try and implement game logic within my current architecture?
As I see your goal, you could just store movementFactor field in fighter, and allow to change it from game logic layer. In Physics class delta is then mul-ied by that field. If you use component like system you probably do not want to update components manually, only operate with data.
Logic update order is a complex problem: imagine a chicken falling on an egg. It happens that in the same frame chicken touches the egg and egg is ready to show us new little chick. What should be executed first? That depends on what is updated first: physics or eggs, and on the fact whether reactions apply immediately. The best scenario (most fair usually) would be for them not to apply immediately, but form a stack of objects (components) state changes, for them to be resolved independently after the action phase.
Also make sure you do not want to stick with existing entity system like entityx.
Related
I am fairly new to VTK and I really enjoy using it.
Now, I want to interact with multiple objects independently. For example, if I have 5 objects in a render window, I want to only move, rotate and interact with the one selected object; whilst the rest of the 4 objects stay where it is.
At the moment, the camera is doing the magic and as I rotate the independent object, other objects move at the same time and I don't want that to happen.
I also want to store all the objects in memory.
I intend to use C++.
This is my sort of class structure...
class ScreenObjects
{
vtkActor (LinkedList); // I intend on using a linkedlist to store all the actors
public:
ScreenObjects(); // Constructor. Initializes vtkActor to null.
void readSTLFile(); // Reads the STL File
bool setObject(); // Sets current object, so you can only interact with the selected object
}
I am missing quite a lot of functions and detail in my class, as I don't know what else to include that would be of use. I was also thinking of joining two objects together, but again, I don't know how to incorporate that in my class; any information on that would be appreciated.
Would really appreciate it if I could be given ideas. This is something of big interest to me and it would really mean a lot to me, and I mean this deep down from my heart.
First of all you should read some tutorials and presentations like this one for example:
http://www.cs.rpi.edu/~cutler/classes/visualization/F10/lectures/03_interaction.pdf
I say that cause it looks like you're currently just moving the camera.
Then you should look into the VTK examples. They are very helpful for all VTK classes.
Especially for your problem have a look at:
http://www.vtk.org/Wiki/VTK/Examples/Cxx/Interaction/Picking
Basicly you have to create a vtkRenderWindowInteractor derived class to get the mouse events (onMouseDown,onMouseUp,onMouseMove,...).
And a vtkPropPicker to shoot a ray from your mouse position into the 3D view and get the vtkActor.
Now you can store onMouseDown inside your vtkRenderWindowInteractor derived class the vtkActor you'd like to move and the currentMouse position. When the user release the mouse (onMouseUp) just get the new mouse position and use the difference of the onMouseDown/onMouseUp positions to modify the vtkActor position.
I've been developing a 2d RPG based on the LWJGL alongside with Java 1.6 for 3 months now. My next goal is to write all of the non-game-ish stuff. This includes menus, text input boxes, buttons and things like the inventory and character information screens. As I am a Computer Engineering student, I'm trying to write everything on my own (except, of course, for the OpenGL part of the LWJGL) so that I "test" myself on the writing of a simple 2d game engine.
I know that making such things from scratch requires basically mapping textures to quads (like the buttons), writing stuff on them and testing mouse/keyboard events which trigger other events inside the code.
The doubt I have is: should I use VBO's (as I'm using for the actual game rendering) or Immediate Mode when rendering such elements? I don't really know if Immediate Mode would be such a drop on performance. Another point is: do the interface elements have to be updated as fast as the game itself? I don't think so, because nothing is actually moving... Are actual games made like that?
Immediate Mode is more straightforward for the task, you would not need to take care about caching and controls composition/batching. Performance dropoff is not that big, unless you render a lot of text (thousands of letters) with each glyph in a separate glBegin..glEnd. If you don't use VBO anywhere else I would recommend trying it out for text output and doing everything else in easier Immediate Mode.
GUI elements might not change as often as game state does, but there's a catch - you could need to update them each time there's a cursor interaction (e.g. button gets OnMouseOver event and needs to be rendered with a highlight). These kind of events may happen very frequently, so thats why rendering may be needed at a full speed.
I am at the start of my cocos2d adventure, and have some ideological questions to ask. I am making a small space-shooter game, am I right to use the following class structure?
Scene
Background Layer
Infinite parallax background
Game Layer
Space ships
Bullets
Control Layer
Joystick
Buttons
and a followup question — what is the best practice in accessing objects from other layers? For example, when the joystick is updated, it must rotate the space ship and move the background. Both of these are in other layers. Is there some recommended way to go about this or should I simply get the desired objects by Tag and operate on them?
Cocos is a big singleton-based system, which may not appeal to some developers but is often used in Cocos apps and is the fundamental architecture of the framework. If you have one main scene and many subsequent layers added to that scene, and you want controls from one layer to affect sprites or logic on other layers, there really is nothing wrong with making your main scene a singleton and sending the information from the joystick layer back to the scene to handle for manipulating other layers or sprites. I do this all the the time and this technique is used in countless Cocos tutorials in books and online, so you can feel that you aren't breaking too many rules if you do it this way (and it's also quite easy to do).
If you instead choose to use pointers in one layer to send data to other layers, this can get you into a lot of trouble since one node should never own another node that it doesn't have a specific parent-child relationship with. Doing so can cause crashes and problems with the native Cocos cleanup methods when you remove scenes later, and potentially leak memory. You could use a weak reference in such a case instead, but that is still dependent on one layer expecting another layer to always be around, which may not be the case.
Sending data back to the main game scene to then dispatch and use accordingly is really efficient.
This seems like a perfectly reasonable way to arrange your objects, this is a method I use.
For accessing objects, I would keep an explicit reference to the object as a member variable and use it directly. (Using tags isn't a bad option, I just find it can get a little messy).
#interface Class1 : NSObject
{
CCLayer *backgroundLayer;
CCLayer *contentLayer;
CCLayer *hudLayer;
CCSprite *objectIMayNeedToUseOnBackgroundLayer;
CCNode *objectIMayNeedToUseOnContentLayer;
}
Regarding tags, one method I use to make sure the tag numbers I'm assigning are unique is define an enum as follows:
typedef enum
{
kTag_BackgroundLayer = 100,
kTag_BackgroundImage,
kTag_GameLayer = 200,
kTag_BadGuy,
kTag_GoodGuy,
kTag_Obstacle,
kTag_ControlLayer = 300
kTag_Joystick,
kTag_Buttons
};
Most times I'll also just set zOrder and tag properties of CCNodes (i.e. CCSprites, CCLabelTTFs, etc.) the same, so you can actually use the enum to define your zOrder, too.
I am working on a screen manager for a miniature game engine, and so far I cannot find a proper solution to managing screen objects without using the 'blob' for each one of the screens. Is blob tolerable in such circumstances where I need a list of renderable objects in one controller?
I would consider using the MVC pattern in this situation. Otherwise, if you're not careful, it's very easy to end up with a bunch of spaghetti code where the screen code is reaching into the game code, and vice versa.
I have recently coded something you might call a "screen manager".
I started with the idea that, whatever game I make, the render system is going to be pretty much the same in terms of how to render (how to manage the hardware). The thing that changes is what is rendered, and how to draw it (do I want a box or a circle or a bitmap.. representing what... etc).
So basically the "game state" is responsible for knowing how to render itself, and should do so when given a render surface from the screen manager or graphics system (It should also be responsible for other things like knowing how input, physics, etc act upon itself).
I implemented it with a singleton for the GraphicsSystem object, which was called something like this:
GameState gs;
Graphics::System().Init(DOUBLE_BUFFER, 640, 480);
...
while(still_looping) {
...
// When it is time to render:
Graphics::System().RenderGameState(&gs);
}
And how, you ask, does the Graphics::System() singleton know how to render the game state? It knows because the game state is inherited from a listener exposed by the graphics system...
//within GraphicsSystem.h...
class BaseRenderer
{
public:
virtual void Render(BITMAP *render_surface) = 0;
};
//GameState defined with:
class GameState : public BaseRenderer
{
public:
void Render(BITMAP *render_surface);
...
You can do this with nearly all the subsystems... (probably not timing, as it is needed in the game loop).
Why singletons? Well, it is C++ and I'm assuming there is only 1 screen, or graphics subsystem to render with. I'm not sure if you are using multiple screens, or a mobile phone or a console. The other way I would do it is to have the graphics system as static global variables in a separate file, giving them file scope only, and having accessor functions in that file (my old C way of doing things).
The key though is encapsulation. Let your screen manager manage the hardware. Let your game state dictate how itself should be expressed.
If this misses the point, please clear up your question and I can edit the answer.
Im in the middle of creating my first iPhone game - I have a background in OOP and in particular C++ so I had some questions with regards to how best to logically setup layers while maintaining functionality.
Currently I WANT for my game to have three main layers:
HUDLayer (All static objects on the screen are here - game controls, User score, pause button etc.)
PlayLayer (The Player, the main game loop and all of the game logic here)
Level Layer (The level images and the level physics objects that the player interacts with, and the background music specific to this level)
Notice I used the word WANT here - because for the life of me im constantly having to move logical objects around just to work within what appears to be Cocos2d's and spacemanagers structure.
Below are just some of the issues that I'm facing
I would like for my PlayLayer to be the scene thats loaded by the director - but if I do that then all of the HUDLayer objects get covered behind the PlayLayer, and dont stay in place like they should, hence the HUDLayer is my scene and I have had to do that just to make it work
I would like to play the background music (via simpleAudioEngine playBackgroundMusic) in the LEVEL layer because I want different levels to have different music. So far the ONLY way I have gotten background music to work is to have it in the TOP most layer i.e. in this case the HUDLayer
Because of the fact that I have to use an instance of the SpaceManagerCocos2d object to create physics bodies - it seems like my level layer has to be killed and just incorporated within my PlayLayer otherwise im having a nightmare of a time attempting to detect collisions between the player and the level.
Am I missing something very obvious here? is there a core understanding of layers that Im just not getting? More and more I feel like im being pushed by the framework to build the whole game inside of a single class and just to use layers as scenes.
Is anyone else having these problems? Am I approaching the architecture of the game wrong? Any help would really be appreciated.
Thanks in advance guys!
Well, each game is different. There are many good discussions on the cocos2d forums about architecture, some people prefer to use an MVC approach, some like using an Actor metaphor to contain physics objects, etc.
Here's my approach:
Use two CCLayer objects (GameLayer and HUDLayer) as child nodes of one CCScene (GameScene). These are the "view" objects.
Create a GameController singleton that can make changes to the game state (also stored in GameController, or in a separate file.) You could also subclass CCScene and call that your controller.
GameLayer is in charge of rendering the graphics of the game level and all actors in it; it also handles getting game input via touch events.
HUDLayer is placed at a higher z-index than the GameLayer and obviously has all of the CCSprite objects for the HUD and buttons.
Interaction between the HUDLayer and the GameLayer is managed via the GameController.
GameController does all of the state changing and game actions.
That's just my approach because it worked for my current game, and it by no means is the definitive answer.
I'd suggest that you look into using an Actor paradigm for your physics objects -- SpaceManager does a decent job, but you don't necessarily always want physics objects to extend CCSprite.