opengl-cge

OpenGL C++ game engine for educational purposes

The goal

I'll use this repository to control and share my progress on my understanding of opengl. I'll test my knowledge by building a engine which will only serve as educational purposes.

Building

I still have to look into that. The project currently uses Visual Studio 2015 and opengl 4.3

Features

Application manager

Easily create a window with the specified title, width and height with a singleton.

Constructor

app(GLuint _width, GLuint _height);

Takes as parameters the window width and the window height

Methods

open method
```
void open(int GL_major, int GL_minor, const char * name);
```
The first two parameters specify the major and minor versions of opengl, the third parameter is the new window's name

Usage example:
```
cge::app app(1250, 900);
app.open(4, 3, "opengl engine");
```
shouldClose method
```
int shouldClose();
```
returns 1 if the current application should close. note: There is another method wrapping shouldClose() that should always be used, that is startLoop()

Usage example:
```
cge::app app(1250, 900);
app.open(4, 3, "opengl engine");

while (!app.shouldClose()) {
  // do something...
}
```
startLoop method
```
int startLoop();
```
prepare the application for the next rendering call. Returns 1 if the current application should close. note: this method return the result from the shouldClose() method

Usage example:
```
cge::app app(1250, 900);
app.open(4, 3, "opengl engine");

while (!app.startLoop()) {
  // do something...
}
```

endLoop method

void endLoop();

Swaps the opengl buffer. Internally check if the escape key was pressed to close the application

Usage example:

cge::app app(1250, 900);
app.open(4, 3, "opengl engine");

while (!app.startLoop()) {
  
  app.endLoop();
}

Properties

keys property
```
bool keys[1024];
```
can be used to check if a key was pressed between the last loop iteration and the new one. the event key poll is made at the beginning of the loop in the startLoop() method.
```
while (!app.startLoop()) {
  if (app.keys[GLFW_KEY_W] == true) {
    std::cout << "W key was pressed\n";
  }

  app.endLoop();
}
```

Camera system

A virtual 2D camera system

Constructor

Camera(GLuint width, GLuint height);

takes as parameters the viewport' width and height.

Methods

updateView method

void updateView();

Usage example:

cge::app app(1250, 900);
app.open(4, 3, "opengl engine");
  
cge::Camera camera(app.width, app.height);

while (!app.startLoop()) {
  camera.updateView();
  	
  app.endLoop();
}

Methods

runFollow method

void runFollow();

make the camera follow the followed vector position stored.

Usage example:

cge::app app(1250, 900);
app.open(4, 3, "opengl engine");
  
cge::Camera camera(app.width, app.height);

while (!app.startLoop()) {
  camera.updateView();
  camera.runFollow();
  	
app.endLoop();
}

Properties

followedPosition property
```
glm::vec2 * followedPosition;
```
Vector pointer to the vector position you want the camera to follow when running the runFollow() method.
anchor property
```
glm::vec2 anchor;
```
It is a 2D vector defining the anchor point for the camera's followed position. With the vector [x, y] when set to [0.5, 0.5] the anchor point is set to the center of the viewport.
- X defines the horizontal position from left to right between 0 and 1.
- Y defines the vertical position from top to bottom between 0 and 1.
followSpeed property
```
GLfloat followSpeed;
```
this value should be set between 0 and 1. And defines the number of steps required for the camera to get to the followedPosition

Spritebatch system

Efficient 2D rendering with the spritebatch class

Constructor

SpriteBatch();

usage Example:

cge::SpriteBatch batch;

Methods

begin method
```
void begin();
```
Set up everything to begin the spritebatch collecting
end method
```
void end();
```
Set up everything for the batch.render() method

render method

void render();

uses all the data collected between the begin and end methods to render to the screen the glyphes

Usage example:

cge::app app(1250, 900);
app.open(4, 3, "opengl engine");
  
cge::Camera camera(app.width, app.height);
cge::SpriteBatch batch;

while (!app.startLoop()) {
  batch.begin();

  // rendering calls

  batch.end();
  batch.rener();

  app.endLoop();
}

Textures

Load 2D textures with ResourceManager

Constructor

Texture2D();

usage Example:

cge::Texture2D texture_circle = cge::ResourceManager::LoadTexture("assets/circle.png", GL_TRUE, "circle");

Methods

No methods that should be manually called

Collision classes

You can use the cge::hitbox class to instanciate the hitbox of a 2D sprite.

Constructor

Hitbox(glm::vec2 customSize, glm::vec2 customPosition);

Methods

intersects method
```
bool Hitbox::intersects(Hitbox * obj, glm::vec2 & obj1_position, glm::vec2 obj2_position)
```
return true if this hitbox and the supplied hitbox intersects. As an hitbox can be linked to many elements in a 1 hitbox to many elements relation. The object 1's hitbox and the object 2's hitbox must be passed in the parameters. The object 1 is the one linked to this hitbox, the object 2 is the one linked to the supplied hitbox pointer. note: this method should not be called manually, it is called internally by the Sprite class in the Sprite::intersects method.
resolve method
```
void Hitbox::resolve(Hitbox * obj, glm::vec2 & obj1_position, glm::vec2 obj2_position)
```
Move the two objects so that they don't intersect anymore. note: this mothoud should not be called manually, it is called internally by the Sprite class in the Sprite::intersects method.

Helper

A singleton that provides many helper methods such as FPS count, delta between frames...

Constructor

helper();

Methods

getDelta method

GLfloat getDelta();

return the value of the delta-time between the current frame and the last one. Useful to get framerate independant velocity, camera movement and all.

Usage example:

cge::app app(1250, 900);
app.open(4, 3, "opengl engine");

cge::helper helper;

GLfloat delta = helper.getDelta();
while (!app.startLoop()) {

  delta = helper.getDelta();

  app.endLoop();

}

coutFramerate() method

void coutFramerate();

std::cout the framerate

Usage example:

cge::app app(1250, 900);
app.open(4, 3, "opengl engine");

cge::helper helper;

GLfloat delta = helper.getDelta();
while (!app.startLoop()) {

  delta = helper.getDelta();
  helper.coutFramerate();

  app.endLoop();

}

Texture rendering

Allows the rendering of 2D fixed textures.

Constructor

Sprite();

Sprite(glm::vec2 pos, glm::vec2 size, cge::Texture2D * _texture);

Methods

drawBatch method

virtual void drawBatch(cge::SpriteBatch & spriteBatch);

Usage example

cge::app app(1250, 900);
app.open(4, 3, "opengl engine");

cge::Camera camera(app.width, app.height);
cge::SpriteBatch batch;

cge::Texture2D texture_tile = cge::ResourceManager::LoadTexture("assets/tile.png", GL_TRUE, "tile");

cge::Hitbox tileBox(glm::vec2(100.0f, 100.0f), glm::vec2(0.0f, 0.0f));

cge::Sprite obstacle(glm::vec2(525.0f, 525.0f), glm::vec2(100.0f, 100.0f), &texture_tile);
obstacle.addBox(&tileBox);

while (!app.startLoop()) {
  batch.begin();

  obstacle.drawBatch(batch);

  batch.end();
  batch.rener();

  app.endLoop();
}

addBox method

void addBox(Hitbox * _box);

set the hitbox

Usage example:

cge::Texture2D texture_tile = cge::ResourceManager::LoadTexture("assets/tile.png", GL_TRUE, "tile");

cge::Hitbox tileBox(glm::vec2(100.0f, 100.0f), glm::vec2(0.0f, 0.0f));

cge::Sprite obstacle(glm::vec2(525.0f, 525.0f), glm::vec2(100.0f, 100.0f), &texture_tile);
  obstacle.addBox(&tileBox);

applyAcceleration method
```
void applyAcceleration(const GLfloat delta);
```
Add the value of this->acceleration to this->velocity, then resets the acceleration value. It should be called before this->applyVelocity().
applyVelocity method
```
void applyVelocity(const GLfloat delta);
```
Add the value of this->velocity to this->position. It should be called just before this->drawBatch()
applyFriction method
```
void applyFriction(const GLfloat factor);
```
multiply the velocity by the factor

Animated texture rendering

Spritesheets support with the cge::SpriteSheet class and the cge::AnimationsUV class

AnimationsUv

The AnimationsUv class serves as a storage for animations based on UV coordinates in a spritesheet. You can declare in the spritesheet multiple animations with custom names, custom lengths and durations.

Constructor

AnimationsUV(int _rows, int _columns);

Methods

setAnimation method

AnimationsUV & setAnimation(std::string & name, int _beginX, int _beginY, int _endX, int _endY, float _timePerCell)

add an animation to the registry

Usage example:

cge::AnimationsUV(3, 9).setAnimation(std::string("default"), 0, 0, 6, 0, 1000)

setCurrentAnimation method
```
bool setCurrentAnimation(std::string & name);
```
this method tries to change to a new animation only if a stored animation exists with the same name as the supplied string.
time method
```
void time(float delta);
```
Adds a tick to the counter, automatically changes the current cell if currentTick >= ticksPerCell

SpriteAnimation

Constructor

SpriteAnimation(glm::vec2 pos, glm::vec2 _size, cge::Texture2D * _texture, AnimationsUV _animationsUV);

Methods

drawBatch method

virtual void drawBatch(cge::SpriteBatch & spriteBatch);

time method
```
void time(float delta);
```

Text rendering

Offers easy text rendering with 2 classes

cge::TextManager
cge::Text

Text rendering should be done by first defining a TextManager instance by passing to the init function the windows width and the windows height.

Text Manager

Constructor

TextManager();

Methods

init method

bool init(GLuint width, GLuint height);

Usage example:

cge::app app(1250, 900);
app.open(4, 3, "opengl app");

cge::TextManager textManager;
textManager.init(app.width, app.height);

newText method

Text newText(char* text, GLfloat x = 0, GLfloat y = 0, GLfloat scale = 1, glm::vec3 color = glm::vec3(1, 1, 1));

Usage example:

cge::app app(1250, 900);
app.open(4, 3, "opengl app");

cge::TextManager textManager;
textManager.init(app.width, app.height);

cge::Text textObject = textManager.newText("Hello world", 150, 150);

Text

Constructor

Text(char* text, TextManager * manager, GLfloat x = 0, GLfloat y = 0, GLfloat scale = 1, glm::vec3 color = glm::vec3(1, 1, 1));

Methods

setString method

void setString(char * text);

Usage example:

cge::Text textObject = textManager.newText("Hello world", 150, 150);

textObject.setString("Custom message");

render method

void render();

Usage example:

cge::Text textObject = textManager.newText("Hello world", 150, 150);

textObject.render();

Dependencies

opengl (use the one provided by your operating system)
glfw
glew
SOIL

Aelto/opengl-cge

opengl-cge

The goal

Building

Features

Application manager

Constructor

Methods

Properties

Camera system

Constructor

Methods

Methods

Properties

Spritebatch system

Constructor

Methods

Textures

Constructor

Methods

Collision classes

Constructor

Methods

Helper

Constructor

Methods

Texture rendering

Constructor

Methods

Animated texture rendering

AnimationsUv

Constructor

Methods

SpriteAnimation

Constructor

Methods

Text rendering

Text Manager

Constructor

Methods

Text

Constructor

Methods

Dependencies