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Making Breakout - Code Structure help requested

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I'm following the list of games a begginner should make suggested by Alpha_ProgDes and I'm about to start making Breakout, though this time I'll go the hardcore way with C++ & SDL instead of Unreal Engine.
I'll figure out  how to write the classes and make it work, though I wanted to ask you guys about what I will need to make and how it should be organized, so that I have a clear roadmap that I can breeze trough step by step, without hitting any dead ends :D
So this are my initial thoughts:
●I will need a "Timer" class which keeps track of ms since last frame
●I will need a "Game" class which has a Timer and takes care of initializing the SDL_Window and SDL_Renderer, also with a destructor that takes care to destroy them.
●I will need a "TextureManager" class which containst a map<string, Texture*> to which I can ask for a texture by its name from within other classes, so pretty much every Actor (taking unreal naming for semplicity here) need to include this "TextureManager". Also texture manager destructor takes care of destroying all the textures.
●I need a base Actor class which will contain member variables x,y centered pivot coordinates for the actor sprite, SDL_Rect for the sprite position/size and a Texture* for the sprite, also virtual draw() and virtual update() methods
Well that all I can think for now, I don't have a very clear idea for how the input handling should be done, is just like a super giant switch inside the game loop, or it is like a class "InputManager" that keep track of which actor is interested in which key input and forward the inputs to the approriete actors or... mh... no idea really how it should be done :S
So, whatever feedback or suggestion or "Structure Roadmap" you can present me to put me on the right tracks, is very welcome! :P 
I only need knowledge of a reasonably correct structure and I will fill in the blanks :)

 

Edited by MarcusAseth

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My first suggestion is that you don't need to have a list of classes up-front. If we tried to do that for AAA games we'd never start coding.

My other comments:

  • I like to have a separate App class which contains a Game class. Game is for, well, gamey things. I'd create the window and other input/output in the App, as well as an instance of the Game.
  • Actors shouldn't need TextureManagers. There's no part of 'acting' that needs to look up textures. If you want Actors to be responsible for drawing themselves, that's fine (at least at this level), but you should pass in the texture to use in each case.
  • Input handling for a game like this can stay simple. I'd start with a function that is called from the main loop, with the paddle passed in as an argument. Call methods on the paddle to implement movement, based on input state. If you have the separate Game/App system like I do, then the App's input handling can call through to the Game's input handling.

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I usually start at the global picture, instead of the small details. What data do you have, what activities must be done (at high level, so "game map", "textures", "character", and "drawing the screen" is more than enough.

Make big building blocks (eg on a single sheet of paper) where those things roughly go. It should give you an overview of the program as a whole, even though your picture may be wrong, but the only way to find out is by trying to build it.

You will hit dead ends, but it's part of the process. Programs are so complicated, it is impossible to get all the details right on the first try. Don't be afraid of it, learn to recognize it happening, and how to recover from it.

Finally, nobody says you must do all coding in one project. If you want to figure out how to do some detail, eg movement with keys or so, and you don't know how, use paper and your grey matter to work it out. If it needs experimenting, make a small side-program for experiments. When done, apply the knowledge in your main project (which may include code of the experiment, but in general rewriting improves code).

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A classic issue for a lot of people (myself included) is the tendency to over engineer things. Frankly the best way to learn what you need is to just make something and set small goals, milestones if you will. I used to create these really complicated classes before even knowing what I needed, but often it either got thrown away or simply went unused or the architecture changed somewhat so I had to rewrite it anyway. For example, since you're making a breakout game you might just want to start simple, "well I need a game loop and a window, now I need to draw something onscreen, now I need to make a ball, okay now the ball needs to bounce against the edges of the screen and re-spawn."

The first two things you mentioned are fine, for the texture manager I would question if you even need one. Is the game complex enough that sprites require managing? Honestly in most arcade games that isn't the case, sprites may be used only once and the entire game contains a small enough number of them for you to simply load them all in some function and pass them around. Important questions are things like -when- to load them too, if you can you might as well load them all at the start. Frankly unless you KNOW for a fact that you need something to be complex, it is almost always better to start off simple and build up from there.

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Thank you for answering guys :)

Quote

The first two things you mentioned are fine, for the texture manager I would question if you even need one. Is the game complex enough that sprites require managing?

Frankly unless you KNOW for a fact that you need something to be complex, it is almost always better to start off simple and build up from there.

I see that point, though my point would be that all the games in the list of games a begginner should make seems like they don't require a TextureManager as well, so even if I don't need a TextureManager right now or to learn how to make a Singleton, when do I get to learn it then?! :P

I am kind of throwing extra stuff in exactly because the project is simple, so the scale is small and I can learn this concepts in realive comfort/safety.

So from my point of view, I actually value something that over-complicate the project if it is just for the sake of learning a new thing, basically making this game is not really the main goal. So if you guys think I could research and apply an interesting design pattern to this project feel free to suggest, because for me is an opportunity to fiinally learn a new/useful thing :P 

Edited by MarcusAseth

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3 minutes ago, MarcusAseth said:

I see that point, though my point would be that all the games in the list of games a begginner should make seems like they don't require a TextureManager as well, so even if I don't need a TextureManager right now or to learn how to make a Singleton, when do I get to learn it then?!

I am kind of throwing extra stuff in exactly because the project is simple, so the scale is small and I can learn this concepts in realive comfort/safety.

So from my point of view, I actually value something that over-complicate the project if it is just for the sake of learning a new thing, basically making this game is not really the main goal. So if you guys think I could research and apply an interesting design pattern to this project feel free to suggest, because for me is an opportunity to fiinally learn a new/useful thing  

Which is fine, I experiment with ideas myself on a regular basis, the problem is it becomes easy for you to start doing that for everything. Particularly when it is that, experimenting, you can quickly get in over your head and make the code a mess of things you aren't sure are good architecture, and dig yourself into a corner that it feels frustrating to get out of.

Sometimes it might be better to experiment on standalone tech demos and things, or to save writing something complex like that until you actually need it. That's a bit of an unspoken rule that people don't often actually explain, software only gets complicated because it needs to. If you could write the next Battlefield game just by making a function that loads all the game data at the start and not bother with subsystems dedicated to managing things, then they probably would.

You might want to consider that the faster you finish a game the faster you get to try another project as well, and possibly explore more concepts or have more challenging rules to write for.

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6 minutes ago, MarcusAseth said:

all the games in the list of games a begginner should make seems like they don't require a TextureManager as well, so even if I don't need a TextureManager right now or to learn how to make a Singleton, when do I get to learn it then?!

  1. Maybe you never need a TextureManager....
  2. You CERTAINLY don't need a Singleton.
  3. On that list, Ikari Warriors and Super Mario Bros have sufficient numbers of sprites and graphics to make some sort of image asset management worthwhile.
  4. The point of following a list like this in order is that each one introduces new challenges. As the article says, this time around you'll be learning "Lessons of pong, powerups, maps (brick arrangements)". Those are the things you probably want to focus on - how should they be implemented?

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Done some progress, I'm thinking to paste here the code I write during this project in case someone notices and point out some ugly stuff I may end up doing so that I avoid ending up with bad coding habits.

I'll put it into spoiler just to not flood the entire page with a single reply :S

The only problem I am currently having is inside Game.cpp, code below:

#define BACKGROUND "Graphics/Background.png";
#define PADDLE "Graphics/Paddle.png";
#define BALL "Graphics/Ball.png";

Game::Game(SDL_Window* Window, SDL_Renderer* Renderer)
	:Window{ Window }, Renderer{ Renderer }
{
	LoadImage(BACKGROUND);
	LoadImage(PADDLE);
	LoadImage(BALL);
}

LoadImage takes a const char* but those 3 macro are not expanding into that for some reason, since VS is giving me a red squigly line... what argument type should that function take in order to work with my Macros? :S


 

Spoiler

 

main.cpp


#include <iostream>
#include "SDL2\SDL.h"
#include "SDL2\SDL_image.h"
#include "App.h"

int main(int argc, char* argv[])
{
	App GameClient;

	while (GameClient.IsRunning())
	{

	}

	return 0;
}

App.h


#pragma once
#include "SDL2\SDL.h"
#include "Game.h"
class App
{
	bool Running = false;
	Uint32  Width = 1280;
	Uint32  Height = 960;
	Uint32  WinFlags = 0;
	Uint32  RenFlags = SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC;
	SDL_Window* Window;
	SDL_Renderer* Renderer;
	Game* GameInstance;

	bool Init();
	bool CreateWindow();
	bool CreateRenderer();
public:
	App();
	~App();
	
	App(const App&) = delete;
	App& operator=(const App&) = delete;
	
	App(App&&) = delete;
	App& operator=(App&&) = delete;
	
	////
	
	inline bool IsRunning()const { return Running; }
};

App.cpp


#include "App.h"
#include "Utility.h"


App::App()
	:Window{ nullptr }, Renderer{ nullptr }
{
	Running = Init();
	
	if (Running)
	{GameInstance = new Game(Window, Renderer);}
}


App::~App()
{
	if (Window) { SDL_DestroyWindow; }
	if (Renderer) { SDL_DestroyRenderer; }
	delete GameInstance;
	SDL_Quit();
}

bool App::Init()
{
	if ( 0 != SDL_Init(SDL_INIT_EVERYTHING)){ return Error(SDL_GetError()); }

	return CreateWindow() ? (CreateRenderer() ? true : false) : (false);
}

bool App::CreateWindow()
{
	Window = SDL_CreateWindow("Breakout",
							  SDL_WINDOWPOS_CENTERED,
							  SDL_WINDOWPOS_CENTERED,
							  Width, Height, WinFlags);
	return Window ? true : Error(SDL_GetError());
}

bool App::CreateRenderer()
{
	Renderer = SDL_CreateRenderer(Window, -1, RenFlags);
	return Renderer ? true : Error(SDL_GetError());
}

Game.h


#pragma once
#include <map>
#include <string>
#include "SDL2\SDL.h"

class Game
{
	SDL_Window* Window;
	SDL_Renderer* Renderer;
	std::map<std::string, SDL_Texture*> Textures;

	bool LoadImage(const char* path);
public:
	Game(SDL_Window* Window, SDL_Renderer* Renderer);
	~Game();

	Game(const Game&) = delete;
	Game& operator=(const Game&) = delete;

	Game(Game&&) = delete;
	Game& operator=(Game&&) = delete;

	////

	SDL_Texture* GetTexture(const char* path)const;
};

Game.cpp


#include "Game.h"
#include "Utility.h"
#include "SDL2\SDL_image.h"

#define BACKGROUND "Graphics/Background.png";
#define PADDLE "Graphics/Paddle.png";
#define BALL "Graphics/Ball.png";

Game::Game(SDL_Window* Window, SDL_Renderer* Renderer)
	:Window{ Window }, Renderer{ Renderer }
{
	LoadImage(BACKGROUND);
	LoadImage(PADDLE);
	LoadImage(BALL);
}


Game::~Game()
{
	for (auto& elem : Textures)
	{ SDL_DestroyTexture(elem.second); }
}

bool Game::LoadImage(const char * path)
{
	if (Textures.find(path) != Textures.end())
	{ return  Error("Ettempting to Load an already Loaded Texture."); }

	SDL_Surface* Surface = IMG_Load(path);
	if (Surface)
	{
		Textures[path] = SDL_CreateTextureFromSurface(Renderer, Surface);
		SDL_FreeSurface(Surface);
		return true;
	}
	else
	{ return Error(SDL_GetError()); }
}

SDL_Texture* Game::GetTexture(const char* path)const
{
	auto& Texture = Textures.find(path);
	return (Texture != Textures.end()) ? Texture->second : nullptr;
}

Actor.h


#pragma once
#include "SDL2\SDL.h"
#include "Game.h"

enum class PivotMode: Uint8 {CENTER,TOP_LEFT};

class Actor
{
SDL_Texture* RequestTexture(const char* path)const;
void SetSpriteRect(Uint32 x, Uint32 y, PivotMode InputMode);
protected:
	Uint32 XCenter;
	Uint32 YCenter;
	SDL_Rect SpriteRect;
	SDL_Texture* Sprite;
	Game* GameRef;
public:
	Actor(Game* GameRef, PivotMode InputMode, Uint32 x, Uint32 y, const char* path);
	virtual ~Actor();

	Actor(const Actor&) = delete;
	Actor& operator=(const Actor&) = delete;

	Actor(Actor&&) = delete;
	Actor& operator=(Actor&&) = delete;

	////
};

Actor.cpp


#include "Actor.h"

#define BACKGROUND "Graphics/Background.png";
#define PADDLE "Graphics/Paddle.png";
#define BALL "Graphics/Ball.png";


Actor::Actor(Game* GameRef,PivotMode InputMode, Uint32 x, Uint32 y, const char* path)
	:GameRef{ GameRef }
{
	if (GameRef)
	{Sprite = RequestTexture(path);}

	if (Sprite)
	{SetSpriteRect(x, y, InputMode);}
}


Actor::~Actor()
{
}

SDL_Texture* Actor::RequestTexture(const char* path)const
{
	return GameRef->GetTexture(path);
}

void Actor::SetSpriteRect(Uint32 x, Uint32 y, PivotMode InputMode)
{
	SDL_QueryTexture(Sprite, NULL, NULL, &SpriteRect.w, &SpriteRect.h);
	switch (InputMode)
	{
		case PivotMode::CENTER:
		{
			SpriteRect.x = x - SpriteRect.w / 2;
			SpriteRect.y = y - SpriteRect.h / 2;
			XCenter = x;
			YCenter = y;
		}break;
		case PivotMode::TOP_LEFT:
		{
			SpriteRect.x = x;
			SpriteRect.y = y;
			XCenter = x + SpriteRect.w / 2;
			YCenter = y + SpriteRect.h / 2;
		}break;
	}
}

 


 

 

Edited by MarcusAseth

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53 minutes ago, MarcusAseth said:

Done some progress, I'm thinking to paste here the code I write during this project in case someone notices and point out some ugly stuff I may end up doing so that I avoid ending up with bad coding habits.

 

Don't use macros for constants. Use "const" or "constexpr" (if your version of C++ has it). 

What is the actual error you're getting when you compile? The "red underlines" produced by Visual Studio are produced by the Intellisense compiler, which is (a) different from the compiler that actually builds your code and (b) often wrong.

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I didn't had tried to compile so far (until you asked), otherwise I would have realized that I shouldn't put the ';' at the end of the macro, which was expanding the ';' into LoadImage("Graphics/Background";); :P

Anyway I'll go with constexpr then, thanks :D

 

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      That is another cool feature of Orx text objects: the text can be changed any time, and the object will re-render.
      Finally, when the ufo collides with the pickup, and the pickup is destroyed, the score variable will be increased. The clock will pick up the variable value and set the score object.
      Begin by creating a score variable at the very top of the code:
       
      #include "orx.h" orxOBJECT *ufo; orxCAMERA *camera; int score = 0;  
      Change the comparison code inside the PhysicsEventHandler function to increase the score by 150 points every time a pickup is collected:
       
      if (orxString_SearchString(recipientName, "PickupObject") != orxNULL) { orxObject_SetLifeTime(pstRecipientObject, 0); orxObject_AddSound(pstSenderObject, "PickupSound"); score += 150; } if (orxString_SearchString(senderName, "PickupObject") != orxNULL) { orxObject_SetLifeTime(pstSenderObject, 0); orxObject_AddSound(pstRecipientObject, "PickupSound"); score += 150; }  
      Now we need a way to change the text of the score object. We declared the score object in the Init() function as:
       
      orxObject_CreateFromConfig("ScoreObject");  
      But we really need to create it using an orxOBJECT variable:
       
      scoreObject = orxObject_CreateFromConfig("ScoreObject");  
      And then declare the scoreObject at the top of the file:
       
      #include "orx.h" orxOBJECT *ufo; orxCAMERA *camera; orxOBJECT *scoreObject; int score = 0;  
      Now it is possible to update the scoreObject using our score variable. At the bottom of the Update() function, add the following code:
       
      if (scoreObject) { orxCHAR formattedScore[5]; orxString_Print(formattedScore, "%d", score); orxObject_SetTextString(scoreObject, formattedScore); }  
      First, the block will only execute if there is a valid scoreObject.
      If so, then create a 5 character string. Then print into the string with the score value, effectively converting an int into a string.
      Finally set the score text to the scoreObject using the orxObject_SetTextString function.
      Compile and Run.
      Move the ufo around and collect the pickups to increase the score 150 points at a time.
        Winning the game
      1200 is the maximum amount of points that can be awarded, and that will mean we've won the game.
      If we do win, we want a text label to appear above the ufo, saying “You win!”.
      Like the score object, we need to define a YouWinObject:
       
      [YouWinObject] Graphic = YouWinTextGraphic Position = (0, -60, 0.0) Scale = 2.0 Smoothing = false  
      Just like the camera, the YouWinObject is going to be parented to the ufo too. This will give the appearance that the YouWinObject is part of the ufo.
      The Scale is set to x2.
      The Position is set offset up in the y axis so that it appears above the ufo.
      Next, the actual YouWinTextGraphic:
       
      [YouWinTextGraphic] Text = YouWinText Pivot = center  
      And the text to render into the YouWinTextGraphic:
       
      [YouWinText] String = You Win!  
      We'll test it by creating an instance of the YouWinObject, putting it into a variable, and then parent it to the ufo in the Init() function:
       
      orxObject_CreateFromConfig("PickupObjects"); scoreObject = orxObject_CreateFromConfig("ScoreObject"); ufoYouWinTextObject = orxObject_CreateFromConfig("YouWinObject"); orxObject_SetParent(ufoYouWinTextObject, ufo);  
      Then the variable:
       
      #include "orx.h" orxOBJECT *ufo; orxCAMERA *camera; orxOBJECT *ufoYouWinTextObject; orxOBJECT *scoreObject; int score = 0;  
      Compile and Run.
      The “You win” text should appear above the ufo. Not bad, but the text is rotating with the ufo much like the camera was before.

      We can ignore the rotation from the parent on this object too:
       
      [YouWinObject] Graphic = YouWinTextGraphic Position = (0, -60, 0.0) Scale = 2.0 Smoothing = false IgnoreFromParent = rotation  
      Re-run. Interesting. It certainly isn't rotating with the ufo, but its position is still being taken from the ufo's rotation.

      We need to ignore this as well:
       
      [YouWinObject] Graphic = YouWinTextGraphic Position = (0, -60, 0.0) Scale = 2.0 Smoothing = false IgnoreFromParent = position.rotation rotation  
      Good that's working right.

      We want the “You Win!” to appear once all pickups are collected.
      The YouWinObject object on created on the screen when the game starts. But we don't want it to appear yet. Only when we win. Therefore, we need to disable the object immediately after it is created using the orxObject_Enable function:
       
      ufoYouWinTextObject = orxObject_CreateFromConfig("YouWinObject"); orxObject_SetParent(ufoYouWinTextObject, ufo); orxObject_Enable(ufoYouWinTextObject, orxFALSE);  
      Finally, all that is left to do is add a small check in the PhysicsEventHandler function to test the current score after each pickup collision:
       
      if (orxString_SearchString(recipientName, "PickupObject") != orxNULL) { orxObject_SetLifeTime(pstRecipientObject, 0); orxObject_AddSound(pstSenderObject, "PickupSound"); score += 150; } if (orxString_SearchString(senderName, "PickupObject") != orxNULL) { orxObject_SetLifeTime(pstSenderObject, 0); orxObject_AddSound(pstRecipientObject, "PickupSound"); score += 150; } if (orxObject_IsEnabled(ufoYouWinTextObject) == orxFALSE && score == 1200) { orxObject_Enable(ufoYouWinTextObject, orxTRUE); }  
      We are checking two things: that the ufoYouWinTextObject is not yet enabled using the orxObject_IsEnabled function, and if the score is 1200.
      If both conditions are met, enable the ufoYouWinTextObject.
      Compile and run.
      Move the ufo around and collect all the pickups. When all are picked up and 1200 is reached, the “You Win!” text should appear above the ufo signifying that the game is over and we have won.

      And that brings us to the end! We have created a simple and complete game with some configuration and minimal code.
      Congratulations!
      I hope you enjoyed working through making the ufo game using the Orx Portable Game Engine. Of course, there are many little extras you can add to give your game that little extra polish. So, for just a bit more eye candy, there a couple more sections that you can follow along with if you wish.
        Shadows
      There are many ways to do shadows. One method is to use shaders… though this method is a little beyond this simple guide.
      Another method, when making your graphics, would be to add an alpha shadow underneath. This is a good method if your object does not need to rotate or flip.
      The method I will show you in this chapter is to have a separate shadow object as a child of an object. And in order to remain independent of rotations, the children will ignore rotations from the parent.
      First a shadow graphic for the ufo, and one for the pickups:
       
      Save these both into the data/texture folder.
      Then create config for the ufo shadow:
       
      [UfoShadowGraphic] Texture = ufo-shadow.png Alpha = 0.3 Pivot = center  
      The only interesting part is the Alpha property. 0.1 would be almost completely see-through (or transparent), and 1.0 is not see-through at all, which is the regular default value for a graphic. 0.3 is fairly see-through.
       
      [UfoShadowObject] Graphic = UfoShadowGraphic Position = (20, 20, 0.05)  
      Set the Position a bit to the right, and downwards.
      Next, add the UfoShadowObject as a child of the UfoObject:
       
      [UfoObject] Graphic = UfoGraphic Position = (0,0, -0.1) Body = UfoBody AngularVelocity = 200 UseParentSpace = position SoundList = AppearSound ChildList = UfoShadowObject  
      Run the project.
      The shadow child is sitting properly behind the ufo but it rotates around the ufo, until it ends up at the bottom left which is not correct.

      We'll need to ignore the rotation from the parent:
       
      [UfoShadowObject] Graphic = UfoShadowGraphic Position = (20, 20, 0.05) IgnoreFromParent = position.rotation rotation  
      Not only do we need to ignore the rotation of ufo, we also need to ignore the rotation position of the ufo.
      Re-run and the shadow sits nice and stable to the bottom right of the ufo.

      Now to do the same with the pickup shadow:
       
      [PickupShadowGraphic] Texture = pickup-shadow.png Alpha = 0.3 Pivot = center [PickupShadowObject] Graphic = PickupShadowGraphic Position = (20, 20, 0.05) IgnoreFromParent = position.rotation  
      The only difference between this object and the ufo shadow, is that we want the pickup shadow to take the rotation value from the parent. But we do not want to take the position rotation.
      That way, the pickup shadow will remain in the bottom right of the pickup, but will rotate nicely in place.
      Now attach as a child to the pickup object:
       
      [PickupObject] Graphic = PickupGraphic FXList = RotateFX Body = PickupBody ChildList = PickupShadowObject  
      Re-run, and the shadows should all be working correctly.

      And that really is it this time. I hope you made it this far and that you enjoyed this series of articles on the Orx Portable Game Engine.
      If you like what you see and would like to try out a few more things with Orx, head over our learning wiki where you can follow more beginner guides, tutorials and examples.
      You can always get the latest news on Orx at the official website.
      If you need any help, you can get in touch with the community on gitter, or at the forum. They're a friendly helpful bunch over there, always ready to welcome newcomers and assist with any questions.
       
       
    • By sausagejohnson
      Creating Pickup Objects
      This is part 4 of a series on creating a game with the Orx Portable Game Engine. Part 1 is here, and part 3 is here.
      In our game, the player will be required to collect objects scattered around the playfield with the ufo.
      When the ufo collides with one, the object will disappear, giving the impression that it has been picked up.
      Begin by creating a config section for the graphic, and then the pickup object:
       
      [PickupGraphic] Texture = pickup.png Pivot = center [PickupObject] Graphic = PickupGraphic  
      The graphic will use the image pickup.png which is located in the project's data/object folder.
      It will also be pivoted in the center which will be handy for a rotation effect later.
      Finally, the pickup object uses the pickup graphic. Nice and easy.
      Our game will have eight pickup objects. We need a simple way to have eight of these objects in various places.
      We will employ a nice trick to handle this. We will make an empty object, called PickupObjects which will hold eight copies of the pickup object as child objects.
      That way, wherever the parent is moved, the children move with it.
      Add that now:
       
      [PickupObjects] ChildList = PickupObject1 # PickupObject2 # PickupObject3 # PickupObject4 # PickupObject5 # PickupObject6 # PickupObject7 # PickupObject8 Position = (-400, -300, -0.1)  
      This object will have no graphic. That's ok. It can still act like any other object.
      Notice the position. It is being positioned in the top left hand corner of the screen. All of the child objects PickupObject1 to PickupObject8 will be positioned relative to the parent in the top left corner.
      Now to create the actual children. We'll use the inheritance trick again, and just use PickupObject as a template:
       
      [PickupObject1@PickupObject] Position = (370, 70, -0.1) [PickupObject2@PickupObject] Position = (210, 140, -0.1) [PickupObject3@PickupObject] Position = (115, 295, -0.1) [PickupObject4@PickupObject] Position = (215, 445, -0.1) [PickupObject5@PickupObject] Position = (400, 510, -0.1) [PickupObject6@PickupObject] Position = (550, 420, -0.1) [PickupObject7@PickupObject] Position = (660, 290, -0.1) [PickupObject8@PickupObject] Position = (550, 150, -0.1)  
      Each of the PickupObject* objects uses the properties defined in PickupObject. And the only difference between them are their Position properties.
      The last thing to do is to create an instance of PickupObjects in code in the Init() function:
       
      orxObject_CreateFromConfig("PickupObjects");  
      Compile and Run.
      Eight pickup objects should appear on screen. Looking good.

      It would look good if the pickups rotated slowly on screen, just to make them more interesting. This is very easy to achieve in Orx using FX.
      FX can also be defined in config.
      FX allows you to affect an object's position, colour, rotation, scaling, etc, even sound can be affected by FX.
      Change the PickupObject by adding a FXList property:
       
      [PickupObject] Graphic = PickupGraphic FXList = SlowRotateFX  
      Clearly being an FXList you can have many types of FX placed on an object at the same time. We will only have one.
      An FX is a collection of FX Slots. FX Slots are the actual effects themselves. Confused? Let's work through it. First, the FX:
       
      [SlowRotateFX] SlotList = SlowRotateFXSlot Loop = true  
      This simply means, use some effect called SlowRotateFXSlot, and when it is done, do it again in a loop.
      Next the slot (or effect):
       
      [SlowRotateFXSlot] Type = rotation StartTime = 0 EndTime = 10 Curve = linear StartValue = 0 EndValue = 360  
      That's a few properties. First, the Type, which is a rotation FX.
      The total time for the FX is 10 seconds, which comes from the StartTime and EndTime properties.
      The Curve type is linear so that the values changes are done so in a strict and even manner.
      And the values which the curve uses over the 10 second period starts from 0 and climbs to 360.
      Re-run and notice the pickups now turning slowly for 10 seconds and then repeating.
       
      Picking up the collectable objects
      Time to make the ufo collide with the pickups. In order for this to work (just like for the walls) the pickups need a body.
      And the body needs to be set to collide with a ufo and vice versa.
      First a body for the pickup template:
       
      [PickupObject] Graphic = PickupGraphic FXList = SlowRotateFX Body = PickupBody  
      Then the body section itself:
       
      [PickupBody] Dynamic = false PartList = PickupPart  
      Just like the wall, the pickups are not dynamic. We don't want them bouncing and traveling around as a result of being hit by the ufo. They are static and need to stay in place if they are hit.
      Next to define the PickupPart:
       
      [PickupPart] Type = sphere Solid = false SelfFlags = pickup CheckMask = ufo  
      The pickup is sort of roundish, so we're going with a spherical type.
      It is not solid. We want the ufo to able to pass through it when it collides. It should not influence the ufo's travel at all.
      The pickup is given a label of pickup and will only collide with an object with a label of ufo.
      The ufo must reciprocate this arrangement (just like a good date) by adding pickup to its list of bodypart check masks:
       
      [UfoBodyPart] Type = sphere Solid = true SelfFlags = ufo Friction = 1.2 CheckMask = wall # pickup  
      This is a static bodypart, and we have specified collision actions to occur if the ufo collides with a pickup. But it's a little difficult to test this right now. However you can turn on the debug again to check the body parts:
       
      [Physics] Gravity = (0, 0, 0) ShowDebug = true  
      Re-run to see the body parts.

      Switch off again:
       
      [Physics] Gravity = (0, 0, 0) ShowDebug = false  
      To cause a code event to occur when the ufo hits a pickup, we need something new: a physics hander. The hander will run a function of our choosing whenever two objects collide.
      We can test for these two objects to see if they are the ones we are interested in, and run some code if they are.
      First, add the physics hander to the end of the Init() function:
       
      orxClock_Register(orxClock_FindFirst(orx2F(-1.0f), orxCLOCK_TYPE_CORE), Update, orxNULL, orxMODULE_ID_MAIN, orxCLOCK_PRIORITY_NORMAL); orxEvent_AddHandler(orxEVENT_TYPE_PHYSICS, PhysicsEventHandler);  
      This will create a physics handler, and should any physics event occur, (like two objects colliding) then a function called PhysicsEventHandler will be executed.
      Our new function will start as:
       
      orxSTATUS orxFASTCALL PhysicsEventHandler(const orxEVENT *_pstEvent) { if (_pstEvent->eID == orxPHYSICS_EVENT_CONTACT_ADD) { orxOBJECT *pstRecipientObject, *pstSenderObject; /* Gets colliding objects */ pstRecipientObject = orxOBJECT(_pstEvent->hRecipient); pstSenderObject = orxOBJECT(_pstEvent->hSender); const orxSTRING recipientName = orxObject_GetName(pstRecipientObject); const orxSTRING senderName = orxObject_GetName(pstSenderObject); orxLOG("Object %s has collided with %s", senderName, recipientName); return orxSTATUS_SUCCESS; } }  
      Every handler function passes an orxEVENT object in. This structure contains a lot of information about the event.
      The eID is tested to ensure that the type of physics event that has occurred is a orxPHYSICS_EVENT_CONTACT_ADD which indicates when objects collide.
      If true, then two orxOBJECT variables are declared, then set from the orxEVENT structure. They are passed in as the hSender and hRecipient objects.
      Next, two orxSTRINGs are declared and are set by getting the names of the objects using the orxObject_GetName function. The name that is returned is the section name from the config.
      Potential candidates are: UfoObject, BackgroundObject, and PickupObject1 to PickupObject8.
      The names are then sent to the console.
      Finally, the function returns orxSTATUS_SUCCESS which is required by an event function.
      Compile and run.
      If you drive the ufo into a pickup or the edge of the playfield, a message will display on the console. So we know that all is working.

      Next is to add code to remove a pickup from the playfield if the ufo collides with it. Usually we could compare the name of one object to another and perform the action.
      In this case, however, the pickups are named different things: PickupObject1, PickupObject2, PickupObject3… up to PickupObject8.
      So we will need to actually just check if the name contains “PickupObject” which will match well for any of them.
      In fact, we don't need to test for the “other” object in the pair of colliding objects. Ufo is a dynamic object and everything else on screen is static. So if anything collides with PickupObject*, it has to be the ufo. Therefore, we won't need to test for that.
      First, remove the orxLOG line. We don't need that anymore.
      Change the function to become:
       
      orxSTATUS orxFASTCALL PhysicsEventHandler(const orxEVENT *_pstEvent) { if (_pstEvent->eID == orxPHYSICS_EVENT_CONTACT_ADD) { orxOBJECT *pstRecipientObject, *pstSenderObject; /* Gets colliding objects */ pstRecipientObject = orxOBJECT(_pstEvent->hRecipient); pstSenderObject = orxOBJECT(_pstEvent->hSender); const orxSTRING recipientName = orxObject_GetName(pstRecipientObject); const orxSTRING senderName = orxObject_GetName(pstSenderObject); if (orxString_SearchString(recipientName, "PickupObject") != orxNULL) { orxObject_SetLifeTime(pstRecipientObject, 0); } if (orxString_SearchString(senderName, "PickupObject") != orxNULL) { orxObject_SetLifeTime(pstSenderObject, 0); } } return orxSTATUS_SUCCESS; }  
      You can see the new code additions after the object names.
      If an object name contains the word “PickupObject”, then the ufo must have collided with it. Therefore, we need to kill it off. The safest way to do this is by setting the object's lifetime to 0.
      This will ensure the object is removed instantly and deleted by Orx in a safe manner.
      Notice that the test is performed twice. Once, if the pickup object is the sender, and again if the object is the recipient.
      Therefore we need to check and handle both.
      Compile and run.
      Move the ufo over the pickups and they should disappear nicely.

      We'll leave it there for the moment. In the final, Part 5, we'll cover adding sounds, a score, and winning the game.
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