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• ### Similar Content

• By abarnes
Hello All!
I am currently pursuing a degree in video game programming, so far I have completed an intro to programming course and object oriented programming course. Both were taught using C++ as the programming langauge which I know is very popular for game development, but in these classes we do not actually do any game development. I would like to start to build my skills with C++ for game development as that is a common required thing for a job and am looking for ways to do this. Any recommendations such as books to read or youtube videos to watch will be greatly appreciated!
• By Orella
I'm having problems rotating GameObjects in my engine. I'm trying to rotate in 2 ways.
I'm using MathGeoLib to calculate maths in the engine.
First way: Rotates correctly around axis but if I want to rotate back, if I don't do it following the inverse order then rotation doesn't work properly.
e.g:
Rotate X axis 50 degrees, Rotate Y axis 30 degrees -> Rotate Y axis -50 degrees, Rotate X axis -30 degrees. Works.
Rotate X axis 50 degrees, Rotate Y axis 30 degrees -> Rotate X axis -50 degrees, Rotate Y axis -30 degrees. Doesn't.

Code:
void ComponentTransform::SetRotation(float3 euler_rotation) { float3 diff = euler_rotation - editor_rotation; editor_rotation = euler_rotation; math::Quat mod = math::Quat::FromEulerXYZ(diff.x * DEGTORAD, diff.y * DEGTORAD, diff.z * DEGTORAD); quat_rotation = quat_rotation * mod; UpdateMatrix();  } Second way: Starts rotating good around axis but after rotating some times, then it stops to rotate correctly around axis, but if I rotate it back regardless of the rotation order it works, not like the first way.

Code:
void ComponentTransform::SetRotation(float3 euler_rotation) { editor_rotation = euler_rotation; quat_rotation = math::Quat::FromEulerXYZ(euler_rotation.x * DEGTORAD, euler_rotation.y * DEGTORAD, euler_rotation.z * DEGTORAD); UpdateMatrix();  }
Rest of code:
#define DEGTORAD 0.0174532925199432957f void ComponentTransform::UpdateMatrix() { if (!this->GetGameObject()->IsParent()) { //Get parent transform component ComponentTransform* parent_transform = (ComponentTransform*)this->GetGameObject()->GetParent()->GetComponent(Component::CompTransform); //Create matrix from position, rotation(quaternion) and scale transform_matrix = math::float4x4::FromTRS(position, quat_rotation, scale); //Multiply the object transform by parent transform transform_matrix = parent_transform->transform_matrix * transform_matrix; //If object have childs, call this function in childs objects for (std::list<GameObject*>::iterator it = this->GetGameObject()->childs.begin(); it != this->GetGameObject()->childs.end(); it++) { ComponentTransform* child_transform = (ComponentTransform*)(*it)->GetComponent(Component::CompTransform); child_transform->UpdateMatrix(); } } else { //Create matrix from position, rotation(quaternion) and scale transform_matrix = math::float4x4::FromTRS(position, quat_rotation, scale); //If object have childs, call this function in childs objects for (std::list<GameObject*>::iterator it = this->GetGameObject()->childs.begin(); it != this->GetGameObject()->childs.end(); it++) { ComponentTransform* child_transform = (ComponentTransform*)(*it)->GetComponent(Component::CompTransform); child_transform->UpdateMatrix(); } } } MathGeoLib: Quat MUST_USE_RESULT Quat::FromEulerXYZ(float x, float y, float z) { return (Quat::RotateX(x) * Quat::RotateY(y) * Quat::RotateZ(z)).Normalized(); } Quat MUST_USE_RESULT Quat::RotateX(float angle) { return Quat(float3(1,0,0), angle); } Quat MUST_USE_RESULT Quat::RotateY(float angle) { return Quat(float3(0,1,0), angle); } Quat MUST_USE_RESULT Quat::RotateZ(float angle) { return Quat(float3(0,0,1), angle); } Quat(const float3 &rotationAxis, float rotationAngleRadians) { SetFromAxisAngle(rotationAxis, rotationAngleRadians); } void Quat::SetFromAxisAngle(const float3 &axis, float angle) { assume1(axis.IsNormalized(), axis); assume1(MATH_NS::IsFinite(angle), angle); float sinz, cosz; SinCos(angle*0.5f, sinz, cosz); x = axis.x * sinz; y = axis.y * sinz; z = axis.z * sinz; w = cosz; } Any help?
Thanks.
• By owenjr
Hi there!
I am trying to implement a basic AI for a Turrets game in SFML and C++ and I have some problems.
This AI follows some waypoints stablished in a Bezier Courve.
In first place, this path was followed only by one enemy. For this purpose, the enemy has to calculate his distance between his actual position
to the next waypoint he has to pick.
If the distance is less than a specific value we stablish, then, we get to the next point. This will repeat until the final destination is reached. (in the submitting code, forget about the var m_go)

Okay, our problem gets when we spawn several enemies and all have to follow the same path, because it produces a bad visual effect (everyone gets upside another).
In order to solve this visual problem, we have decided to use a repulsion vector. The calculus gets like this:

As you can see, we calculate the repulsion vector with the inverse of the distance between the enemy and his nearest neighbor.
Then, we get it applying this to the "theorical" direction, by adding it, and we get a resultant, which is the direction that
our enemy has to follow to not "collide" with it's neighbors. But, our issue comes here:

The enemys get sepparated in the middle of the curve and, as we spawn more enemys, the speed of all of them increases dramatically (including the enemies that don't calculate the repuslion vector).
1 - Is it usual that this sepparation occours in the middle of the trajectory?
2 - Is it there a way to control this direction without the speed getting affected?
3 - Is it there any alternative to this theory?

I submit the code below (There is a variable in Spanish [resultante] which it means resultant in English):

if (!m_pathCompleted) { if (m_currentWP == 14 && m_cambio == true) { m_currentWP = 0; m_path = m_pathA; m_cambio = false; } if (m_neighbors.size() > 1) { for (int i = 0; i < m_neighbors.size(); i++) { if (m_enemyId != m_neighbors[i]->GetId()) { float l_nvx = m_neighbors[i]->GetSprite().getPosition().x - m_enemySprite.getPosition().x; float l_nvy = m_neighbors[i]->GetSprite().getPosition().y - m_enemySprite.getPosition().y; float distance = std::sqrt(l_nvx * l_nvx + l_nvy * l_nvy); if (distance < MINIMUM_NEIGHBOR_DISTANCE) { l_nvx *= -1; l_nvy *= -1; float l_vx = m_path[m_currentWP].x - m_enemySprite.getPosition().x; float l_vy = m_path[m_currentWP].y - m_enemySprite.getPosition().y; float l_resultanteX = l_nvx + l_vx; float l_resultanteY = l_nvy + l_vy; float l_waypointDistance = std::sqrt(l_resultanteX * l_resultanteX + l_resultanteY * l_resultanteY); if (l_waypointDistance < MINIMUM_WAYPOINT_DISTANCE) { if (m_currentWP == m_path.size() - 1) { std::cout << "\n"; std::cout << "[GAME OVER]" << std::endl; m_go = false; m_pathCompleted = true; } else { m_currentWP++; } } if (l_waypointDistance > MINIMUM_WAYPOINT_DISTANCE) { l_resultanteX = l_resultanteX / l_waypointDistance; l_resultanteY = l_resultanteY / l_waypointDistance; m_enemySprite.move(ENEMY_SPEED * l_resultanteX * dt, ENEMY_SPEED * l_resultanteY * dt); } } else { float vx = m_path[m_currentWP].x - m_enemySprite.getPosition().x; float vy = m_path[m_currentWP].y - m_enemySprite.getPosition().y; float len = std::sqrt(vx * vx + vy * vy); if (len < MINIMUM_WAYPOINT_DISTANCE) { if (m_currentWP == m_path.size() - 1) { std::cout << "\n"; std::cout << "[GAME OVER]" << std::endl; m_go = false; m_pathCompleted = true; } else { m_currentWP++; } } if (len > MINIMUM_WAYPOINT_DISTANCE) { vx = vx / len; vy = vy / len; m_enemySprite.move(ENEMY_SPEED * vx * dt, ENEMY_SPEED * vy * dt); } } } } } else { float vx = m_path[m_currentWP].x - m_enemySprite.getPosition().x; float vy = m_path[m_currentWP].y - m_enemySprite.getPosition().y; float len = std::sqrt(vx * vx + vy * vy); if (len < MINIMUM_WAYPOINT_DISTANCE) { if (m_currentWP == m_path.size() - 1) { std::cout << "\n"; std::cout << "[GAME OVER]" << std::endl; m_go = false; m_pathCompleted = true; } else { m_currentWP++; } } if (len > MINIMUM_WAYPOINT_DISTANCE) { vx = vx / len; vy = vy / len; m_enemySprite.move(ENEMY_SPEED * vx * dt, ENEMY_SPEED * vy * dt); } } }
¡¡Thank you very much in advance!!

• Overview
Welcome to the 2D UFO game guide using the Orx Portable Game Engine. My aim for this tutorial is to take you through all the steps to build a UFO game from scratch.
The aim of our game is to allow the player to control a UFO by applying physical forces to move it around. The player must collect pickups to increase their score to win.
I should openly acknowledge that this series is cheekily inspired by the 2D UFO tutorial written for Unity.
It makes an excellent comparison of the approaches between Orx and Unity. It is also a perfect way to highlight one of the major parts that makes Orx unique among other game engines, its Data Driven Configuration System.
You'll get very familiar with this system very soon. It's at the very heart of just about every game written using Orx.
If you are very new to game development, don't worry. We'll take it nice and slow and try to explain everything in very simple terms. The only knowledge you will need is some simple C++.
I'd like say a huge thank you to FullyBugged for providing the graphics for this series of articles.

What are we making?
Visit the video below to see the look and gameplay of the final game:
Getting Orx
The latest up to date version of Orx can be cloned from github and set up with:
git clone https://github.com/orx/orx.git After cloning, an $ORX environment variable will be created automatically for your system which will help with making game projects much easier. It will also create several IDE projects for your operating system: Visual Studio, Codelite, Code::Blocks, and gmake. These Orx projects will allow you to compile the Orx library for use in your own projects. And the$ORX environment variable means that your projects will know where to find the Orx library.
For more details on this step, visit http://orx-project.org/wiki/en/tutorials/cloning_orx_from_github at the Orx learning wiki.
Setting up a 2D UFO Project
Now the you have the Orx libraries cloned and compiled, you will need a blank project for your game. Supported options are: Visual Studio, CodeLite, Code::Blocks, XCode or gmake, depending on your operating system.
Once you have a game project, you can use it to work through the steps in this tutorial.
Orx provides a very nice system for auto creating game projects for you. In the root of the Orx repo, you will find either the init.bat (for Windows) or init.sh (Mac/Linux) command.
Create a project for our 2D game from the command line in the Orx folder and running:
init c:\temp\ufo or
init.sh ~/ufo Orx will create a project for each IDE supported by your OS at the specified location. You can copy this folder anywhere, and your project will always compile and link due to the \$ORX environment variable. It knows where the libraries and includes are for Orx.
Open your project using your favourite IDE from within the ufo/build folder.
When the blank template loads, there are two main folders to note in your solution:
config src Firstly, the src folder contains a single source file, ufo.cpp. This is where we will add the c++ code for the game. The config folder contains configuration files for our game.
What is config?
Orx is a data driven 2D game engine. Many of the elements in your game, like objects, spawners, music etc, do not need to be defined in code. They can be defined (or configured) using config files.
You can make a range of complex multi-part objects with special behaviours and effects in Orx, and bring them into your game with a single line of code. You'll see this in the following chapters of this guide.
There are three ufo config files in the config folder but for this guide, only one will actually be used in our game. This is:
ufo.ini All our game configuration will be done there.
Over in the Orx library repo folder under orx/code/bin, there are two other config files:
CreationTemplate.ini SettingsTemplate.ini These are example configs and they list all the properties and values that are available to you. We will mainly concentrate on referring to the CreationTemplate.ini, which is for objects, sounds, etc. It's good idea to include these two files into your project for easy reference.
Alternatively you can view these online at https://github.com/orx/orx/blob/master/code/bin/CreationTemplate.ini and here: https://github.com/orx/orx/blob/master/code/bin/SettingsTemplate.ini

The code template
Now to take a look at the basic ufo.cpp and see what is contained there.
The first function is the Init() function.
This function will execute when the game starts up. Here you can create objects have been defined in the config, or perform other set up tasks like handlers. We'll do both of these soon.
The Run() function is executed every main clock cycle. This is a good place to continually perform a task. Though there are better alternatives for this, and we will cover those later. This is mainly used to check for the quit key.
The Exit() function is where memory is cleaned up when your game quits. Orx cleans up nicely after itself. We won't use this function as part of this guide.
The Bootstrap() function is an optional function to use. This is used to tell Orx where to find the first config file for use in our game (ufo.ini). There is another way to do this, but for now, we'll use this function to inform Orx of the config.
Then of course, the main() function. We do not need to use this function in this guide.
Now that we have everything we need to get start, you should be able to compile successfully. Run the program and an Orx logo will appear slowly rotating.

Great. So now you have everything you need to start building the UFO game.

Setting up the game assets
Our game will have a background, a UFO which the player will control, and some pickups that the player can collect.
The UFO will be controlled by the player using the cursor keys.
First you'll need the assets to make the game. You can download the file  assets-for-orx-ufo-game.zip which contains:
The background file (background.png):

The UFO and Pickup sprite images (ufo.png and pickup.png):

And a pickup sound effect (pickup.ogg):
pickup.ogg
Copy the .png files into your data/texture folder
Copy the .ogg file into your data/sound folder.
Now these files can be accessed by your project and included in the game.

Setting up the Playfield
We will start by setting up the background object. This is done using config.
Open the ufo.ini config file in your editor and add the following:

[BackgroundGraphic] Texture = background.png Pivot = center
The BackgroundGraphic defined here is called a Graphic Section. It has two properties defined. The first is Texture which has been set as background.png.
The Orx library knows where to find this image, due to the properties set in the Resource section:

[Resource] Texture = ../../data/texture
So any texture files that are required (just like in our BackgroundGraphic section) will be located in the ../../data/texture folder.
The second parameter is Pivot. A pivot is the handle (or sometimes “hotspot” in other frameworks). This is set to be center. The position is 0,0 by default, just like the camera. The effect is to ensure the background sits in the center of our game window.
There are other values available for Pivot. To see the list of values, open the CreationTemplate.ini file in your editor. Scroll to the GraphicTemplate section and find Pivot in the list. There you can see all the possible values that could be used.
top left is also a typical value.
We need to define an object that will make use of this graphic. This will be the actual entity that is used in the game:

[BackgroundObject] Graphic = BackgroundGraphic Position = (0, 0, 0)
The Graphic property is the section BackgroundGraphic that we defined earlier. Our object will use that graphic.
The second property is the Position. In our world, this object will be created at (0, 0, 0). In Orx, the coordinates are (x, y, z). It may seem strange that Orx, being a 2D game engine has a Z axis. Actually Orx is 2.5D. It respects the Z axis for objects, and can use this for layering above or below other objects in the game.
To make the object appear in our game, we will add a line of code in our source file to create it.
In the Init() function of ufo.cpp, remove the default line:
orxObject_CreateFromConfig("Object"); and replace it with:
orxObject_CreateFromConfig("BackgroundObject"); Compile and run.
The old spinning logo is now replaced with a nice tiled background object.

Next, the ufo object is required. This is what the player will control. This will be covered in Part 2.
• By yyam

Hey there! I released my game, Hedgehogs Can Fly, on GameJolt today! It's a cute, 2D physics-platformer where you try to fling a hedgehog through tricky levels to get to the finish line. I wrote it from scratch in C++ with SFML. There are multiple types of terrain each with different properties and effects making for some interesting level design. The physics/level code also allows for free-form terrain that isn't constrained to a tile grid. The levels are loaded from color-coded image files, I have an entry in the devlog on the GameJolt page explaining how it all works!
If these screenshots look cool, visit the GameJolt page here (With Trailer Video!)
Screenshots incoming...

Have a nice day

# C++ Object-oriented vs loop-based programming?

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Hi!

I've been doing games as a hobby in c++ for many years, but have little formal programming education. As a result i might have adopted a rather arcane way of structuring my games. I typically have:

1. A master-class called "world" that is huuge. Keeps track of game state as well as lists for units, buildings, projectiles etc. Some things are the same in many games, but i have a unique world class in every game.
2. Typically: cPlayer player[10]; where player[0] is the player itself in a single-player game and the rest is ai/opponents.
3. A main loop where i do stuff like

if(world.running){
if(world.editorOn)
runEditor();
else
runWorld();
}
else
runLobby();

4. Typically entities like "units" have their own functions like unit::update, unit::move etc, but all of this is held together by the "world"-class.

I guess my thinking is very "loop-based" ei sequencial. Is this problematic? I don't think it's a very modern way of coding.

Thankful for any feedback!
Erik

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If you have a class that is too large, split it up. Ideally each class has only one responsibility. That is something to aspire towards, even if meeting that criteria exactly is unrealistic. I'd recommend that you don't try and plan this all out, but instead get used to improving code as you go along. If you see that a class has several functions that are related to each other, but not related much to the other functions, move them out to a new class. And just keep doing that whenever applicable.

Get into the habit of naming things accurately. e.g. Don't make instances of cPlayer when you're creating an opponent. Think of a better name, such as 'Character' or 'Actor' or 'GameEntity' or whatever most closely resembles the content of that class. And again, if it then turns out that your class is doing 2 things - e.g. player-related things and npc-related things - that's a good candidate for refactoring into more than one class.

Don't use 'magic numbers' to mean things. In this case, that means don't use the zero index to tell the difference between a player and an enemy. What if you ever want to make a 2 player game? Instead, use some property of the object to tell you whether it's a player or not. Or maybe consider having 2 classes, one for players, one for other characters.

Main loops are fine. Everyone has something like one. However you might not want to hard-code your game states (editor/world/lobby) like that. A simple state machine using a switch/case statement is a better alternative. A more advanced alternative might have different objects for each state.

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So,

In order for a program to run for any real duration there must be a loop of some kind, so it's not so much an argument between having many loops or using good OO practice as it is about using good OO practice while having loops.

Most game engines have a relatively simple main loop, that calls a handful of member methods that do some very complex things, in a set order. For example the small game I'm working on at the moment calls a physics step every 10 milliseconds (often not exactly, due to the time it takes the draw frames to complete) but calls a logic and draw step every frame computed.

Within these loops it's common to see something like a std::set<std::shared_ptr<Entity>> of current game entities being looped over and having their 'update()', 'draw()', or 'onCollision()' methods being called, and here is where the good OO practice comes in. Entity is a base class that almost every other entity derives from, be that characters, projectiles, pickups etc.

Because I store pointers to the base class, I can store any derived class within that set and access the virtual methods within the base class. This means I don't need many collections within the world for every different class type.

tl;dl : Looping over collections of OO objects is perfectly fine.

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Well that's another issue: I rarely ever use inheritance. I have specific classes for each game, typically stuff like unit, projectile, map, player, building. I don't find common properties that would benefit from inheritance.

I guess that might be because I'm used to thinking this way i guess.

But what do you gain by inheriting from "entity"? Update and draw function for each one of these must look totally different anyway?

Edited by suliman

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There are usually lots of commonalities across game entities when you think about it. For example, in Unreal, pretty much everything in the world is derived from AActor - so that contains information such as where it is located in the world, where it's facing, where it's moving, etc. Players might be derived from that object; but so could projectiles, or non-player characters, because they all have positions in the world and can potentially move.

You don't necessarily need to use inheritance. Many games use composition to express the fact that entities are roughly interchangeable but with some differing properties. For example, 2 entities could contain different SpriteComponents which dictates how each of them gets drawn. The most important thing about improving your coding is to spot when you can replace special-case solutions with generic and extensible solutions, reducing the amount of code necessary and therefore reducing bugs. That can include replacing explicit if-statements with a state machine, or making the difference between players and non-players explicit rather than dependent on their position within an array, etc. (And this isn't necessarily modernising, because these principles are 40 years old.)

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I have some suggestions:

1:  The most  importent is finish your work  as soon as simple coder.

2:  Not use Complex skills

3:  ''code complete'' read this book,and Reading and Writing code .

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First of all, if your general code structure is working for you, I wouldn't go out of my way to change it, although there are alternatives you could experiment with.

One class with massive state, of which there is a single instance that everyone has a reference or pointer to is indistinguishable from a large collection of global variables, and has exactly the same problems (e.g., it's hard to determine correctness because any part of the code could be changing the global state).

If you don't use inheritance much, I consider that a good sign. There are places where inheritance could make your life easier, but it's easy to overdo, and then the resulting code is very confusing and hard to follow.

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I use composition a lot too and most of my classes are made up of a few interfaces.

Lets look at it this way, consider this: you have many objects that need to be drawn to the screen via a 'draw()' method. You also want to update them every frame to compute their collisions, etc.

We will call the classes Car, Boat, Plane, Man, Box.

Now, without composition or inheritance you would need to have the following arrays:


std::set<Car*> mCars;
std::set<Boat*> mBoats;
std::set<Plane*> mPlanes;
std::set<Man*> mMen;
std::set<Box*> mBoxes;

// Then to update and draw...
for (auto c : mCars)
{
c->update();
c->draw();
}
for (auto c : mBoats)
{
c->update();
c->draw();
}

// Etc.. etc...

This is really messy and breaks the DRY principle of 'Don't Repeat Yourself'.

Lets look at this problem another way.

Although cars and boats and men etc. may have different members and different methods, they all share two common methods, draw() and update(). Each class will implement draw and update differently - for example the car might calculate it's fuel remaining in update() and draw a picture of a car on screen in draw(). Whereas a person might calculate their age in update() and draw a picture of a person in draw();

Because all the classes share these same methods, we can implement an interface that declares these methods, but allows each class to implement it differently.

consider this code (I'll just use Car and Man to save space):

class iGameEntity
{

virtual void draw() = 0;
virtual void update() = 0;
};

class Car : public iGameEntity
{
virtual void draw() override { mRenderWindowPtr->draw("PictureOfCar.png"); }
virtual void update() override { mFuelRemaining -= 1; }
};

class Man : public iGameEntity
{
virtual void draw() override { mRenderWindowPtr->draw("PictureOfMan.png"); }
virtual void update() override { mAge += 1; }
};

// Then we can store all our entities like this
std::set<iGameEntity*> mAllEntities;

// Add some cars and men
mAllEntities.insert(new Car());
mAllEntities.insert(new Car());
mAllEntities.insert(new Man());
mAllEntities.insert(new Man());
mAllEntities.insert(new Man());

// Then to call the methods we simply do this
for (auto e : mAllEntities)
{
e->update();
e->draw();
}

Now, we only need one container, and we only need to loop over it once to call the draw() and update() methods of every game object.

But the real beauty is that every subClass of iGameEntity does something different when draw() or update() is called.

Hope this helps get your head around OO coding.

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Cool, that was a good and clear example

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