- Understanding MiniLibX
- Understanding Textures and Sprites
- Importing and Rendering Textures in MLX
- Collision and Hit Boxes
- Animation
Dino Wars is a game produced by me for my So_Long project at 42, Abu Dhabi. This project is a very small 2D game. Its purpose is to make you work with textures, sprites, and some other very basic gameplay elements.
Gameplay-1.mp4
You can have a look into how the game logic works and also contribute to make it more efficient but leaving sticky notes
Dino Wars Repository, will be the main repo for this games development and updates. This repository is specifically for the project So_long.
Clone the repository, make a bonus, and then run the executable file with the choice of your map in /map folder.
cd so_long
make bonus
./so_long_bonus ./map/map1_bonus.berIn this guide, I will be mainly focusing on creating the game logic, animations and how you can achieve anything using MiniLibX
The best place to start would be MiniLibX Docs, It can be very intimidating at first, but believe me, this tool is a wonder!
Refer to the following sections while going through the MiniLibX Docs
-
Create a new C program and try initializing MLX and a window
-
The part where you create a new image using mlx_new_image() is not necessary, as per my experience you will never be using it. Instead use mlx_pixel_put() to understand how you have control over the MLX window
-
Concepts of colors, little endian, and big-endian were also not used in my project, only initial testing and understanding of MLX involved colors.
-
Your key takeaway from the Getting Started page of MiniLibX would be to successfully understand the initialization of MLX and how you can control the graphics
This project will give you a very simple and easy idea about how you render images onto the MLX Window
The MLX window assigns the position of each pixel using the X and Y positions starting from the top left corner
void render_square(void)
{
int x;
int y;
x = 350;
y = 350;
while (x < 450)
{
while(y < 450)
{
mlx_pixel_put(mlx, win, x, y, color);
y++;
}
y = 350;
x++;
}
}
The above code simply goes through a loop and renders 1 pixel every time with different X and Y positions, resulting in a simple square in your Window
Now that you're aware of how you have access to each and every pixel in your window let's go ahead and see how you can interact with your window
The next section in the MiniLibX Docs about color will not be used, however it's your choice to experiment on that, but I would suggest not spending a lot of time on that section
Loop refers to the infinite loop that goes on infinitely throughout your program. mlx_loop() is the perfect example, it keeps your program running infinitely unless exit() is initiated
Hooks look for the input that you pass through the program, through your mouse or keyboard. MiniLibx has different functions for each input device. However, the best way would be to use mlx_hook() and then assign events as per the prototype. You'll learn about this more in a while.
Events are just the input event that happens, refer to the table below for more information
Integrating inputs are little tricky, there are certain rules you have to go through
The above is a simplified prototype of mlx_hook
-
Mlx and win refer to the pointers
-
Key refers to the input key that you want your program to be looking for (refer to the table below)
-
Mask refers to the key mask (not important, you can learn about this in the end)
-
Function refers to the function you want to call when the key is pressed, your function prototype should match the prototype of the corresponding key (refer to the table below)
-
Parameter is the parameter you will be passing to the Function that is called.
If you notice the prototype column in the table below, the *param is the same parameter that is passed from mlx_hook to the function that is called.
| Key | Event | Prototype |
|---|---|---|
| 2 | Key press | int (*f)(int keycode, void *param) |
| 3 | Key release | int (*f)(int keycode, void *param) |
| 4 | Mouse Click | |
| 5 | Mouse Release | int (*f)(int button, int x, int y, void *param) |
| 6 | Moving Mouse | int (*f)(int x, int y, void *param) |
This table is a mini version of the one you see on MinilibX, these are the ones that are good to start with and then you can progress with more advanced keys depending on your project
This example elaborates on how you can integrate ESC to quit your program
The header defines the keycode that your function will be looking for to quit the game
It's important to use a struct that has all the variables that you use in your program as you can only pass one parameter through your functions
#define ESC = 53 (Defining the keycode of ESC)
typedef struct s_vars{
void *mlx;
void *win;
}t_vars;
The main function starts with initializing mlx and a window, we set the mlx_hook() to look for buttons pressed by passing the key as 2 (refer to the event table) and mask 0 as we won't be needing that
We pass the quit() function as per the prototype (refer event table) with the parameter as vars
It's very important to dynamically allocate memory using malloc and initializing all your variables regardless of memory allocation as you are working with structs and lists, you'll learn about it as we go ahead
int main()
{
t_vars *vars;
vars = NULL;
vars = malloc(sizeof(t_vars));
vars->mlx = mlx_init();
vars->win = mlx_new_window(vars->mlx, 1920 , 1080 , "HELLO");
mlx_hook(vars->win, 2, 0, quit, vars);
mlx_loop(vars->mlx);
}
When any button is pressed quit function initiates, but unless the key is ESC it won't quit
int quit(int keycode, t_vars *vars)
{
if (keycode == ESC)
{
mlx_destroy_window(vars->mlx, vars->win);
free(vars);
exit();
}
}
The above code should stop the program and exit whenever ESC is pressed
Remember how we created a square box using mlx_pixel_put(), lets move the box using the same logic of keys
Let's add some more variables for the position of our square into our struct, and define some more macros for movement buttons
#define ESC 53
#define W 13
#define A 0
#define S 1
#define D 2
typedef struct s_vars{
void *mlx;
void *win;
int box_x;
int box_y;
}t_vars;
Let's use the render function for square, but this time with x + vars->box_x and y + vars->box_y in x and y for mlx_pixel_put()
int render_square(t_vars *vars)
{
int x;
int y;
x = 350;
y = 350;
while(x < 450)
{
while(y < 450)
{
mlx_pixel_put(vars->mlx, vars->win, x + vars->box_x, y + vars->box_y, 0xFFDDFF);
y++;
}
y = 350;
x++;
}
return(1);
}
Let's change our quit function to a keys function and add movement keys to it too, every time you press any movement keys, it changes its position by 10 pixels
int keys(int keycode, t_vars *vars)
{
if (keycode == ESC)
{
mlx_destroy_window(vars->mlx, vars->win);
free(vars);
exit();
}
if (keycode == W)
vars->box_y -= 10;
if (keycode == A)
vars->box_x -= 10;
if (keycode == S)
vars->box_y += 10;
if (keycode == D)
vars->box_x += 10;
}
We'll add mlx_loop_hook() for our render function, it will infinitely call our render function, while at the same time keeping in account the position of our box using box_x and box_y
int main()
{
t_vars *vars;
vars = NULL;
vars = malloc(sizeof(t_vars));
vars->box_x = 0;
vars->box_y = 0;
vars->mlx = mlx_init();
vars->win = mlx_new_window(vars->mlx, 1920 , 1080 , "HELLO");
mlx_loop_hook(vars->mlx, render_square, vars);
mlx_hook(vars->win, 2, 0, keys, vars);
mlx_loop(vars->mlx);
}
Now when you run your program you should be able to move the box, but you'll see a very weird result where the box leaves a trail, and it looks like you're just painting your screen
In fact what we want this
To fix the trial effect, we simply use these two functions which literally do what they say
mlx_clear_window(): Clears the window back to nothing, just a black screen.
mlx_do_sync(): Syncs all the new rendered pixels that are put after rendering, like a refresh button
Just adding mlx_clear_window() before we start to render the pixels and then mlx_do_sync() after we finish the render should fix it for us
int render_square(d_vars *vars)
{
int x;
int y;
x = 350;
y = 350;
mlx_clear_window(vars->mlx, vars->win);
while(x < 450)
{
while(y < 450)
{
mlx_pixel_put(vars->mlx, vars->win, x + vars->x, y + vars->y, 0xFFDDFF);
y++;
}
y = 350;
x++;
}
mlx_do_sync(vars->mlx);
return(1);
}
Congratulations, you successfully have a functional mini-game. Just with these concepts, you can create a full-fledged game like Dino Wars.
Furthermore, in this guide, I will be going through how to work with your own textures and then how you can master animation
Some key points to remember from this exercise
-
It is important to work with structures when it comes to MLX or Game as it gives you too much flexibility
-
Keep track of each and every memory, and initialize every variable in your structures, further on in this guide you will see how we will be connecting different structs and linked lists to each other, in this case, its really important to start the habit of this concept from the base itself
A key feature of a dope game is graphics, it's really important to understand how graphics work and how you can use it to your advantage creatively and make GAME OF THE YEAR!!!!!
Textures are basically images that you use for your game, Sprites are a set of textures that together when sequentially displayed look like a video or animation
| Texture | Sprite (set of textures) |
|---|---|
 |
 |
You can find textures online from websites such as itch.io, you can download textures that you like and then use softwares such as Photoshop or Photopea (Free and Online alternative for Photoshop) to edit your textures
Ideally, we would be going for creating PNGs so that we can convert them to XPM later on and use them in our game
| Right | Wrong |
|---|---|
 |
 |
It's important to make sure that your texture size does not have extra white spaces as it will mess around with the hitbox/collision boundary of your object
When creating sprites it is important that each of your textures is aligned and organized properly with numbering starting from 0
I personally organize it as /player_idle_r/0.png
This might look intimidating and time-consuming but it is very important, better to do it the right way or not do it at all
MLX takes in PNG as well as XPM as input format for texture input. However, using PNG is unstable in MiniLibX, so we convert out textures from PNG to XPM. Use ImageMagick for this, it is a opensource and perfect tool for this project
Now that you have prepared your texture in XPM format for MLX, let's go ahead and import it to your program and then render it in your window
We add another struct and link it to our main struct, you'll see further why we link it to the main struct
void *img: is the pointer to the image that is passed to render on the screen
int w & int h: refers to the width and height of the image that we pass. This is used to calculate the hitbox or collision boundary of your objects
int x & int y: refers to the x and y position of the object that you will be working on width
struct s_obj *next: is a linked list for linking your sprite and animating
#define ESC 53
#define W 13
#define A 0
#define S 1
#define D 2
typedef struct s_obj{
void *img;
int w;
int h;
int x;
int y;
struct s_obj *next;
}t_obj;
typedef struct s_vars{
void *mlx;
void *win;
t_obj *car;
}t_vars;
We allocate memory for our Car and then load the texture to its *img using mlx_xpm_file_to_image()
mlx_xpm_file_to_image() take *mlx, path to your texture, address to store w and h of your image, car->w & car->h in our case
int main()
{
t_vars *vars;
vars = NULL;
vars = malloc(sizeof(t_vars));
vars->car = malloc(sizeof(t_obj));
vars->car->x = 0;
vars->car->y = 0;
vars->car->next = NULL;
vars->car->img = mlx_xpm_file_to_image(vars->mlx, "./texture.xpm", &vars->car->w, &vars->car->h);
vars->mlx = mlx_init();
vars->win = mlx_new_window(vars->mlx, 1920 , 1080 , "HELLO");
mlx_loop_hook(vars->mlx, render_car, vars);
mlx_hook(vars->win, 2, 0, keys, vars);
mlx_loop(vars->mlx);
}
We change our function to render_car and use the *img along with the X and Y position from the object
int render_car(b_vars *vars)
{
int x;
int y;
x = 350;
y = 350;
mlx_clear_window(vars->mlx, vars->win);
while(x < 450)
{
while(y < 450)
{
mlx_put_image_to_window(vars->mlx, vars->win, vars->car->img, vars->car->x, vars->car->y);
}
y++;
}
y = 350;
x++;
}
mlx_do_sync(vars->mlx);
return(1);
}
Now that you are successfully able to put an object inside your game and control it, it is time to understand how you can make it interact with other objects inside your game
The object struct that we created has everything you need to make it interact with other things
Let's assume we have two objects Car and Wall and you don't want the car to move right through the Wall
You have to calculate that the next move is only valid if the Car does not overlap with the Wall
To calculate need to see that the start and the end of the Car i.e car->x and car->x + car->w do not fall under the range of wall->x and wall->x + wall->w.
BUT the above condition should only be valid when car->y and car->y + car->h does not fall in the range of wall->y and wall->y + wall->h
This was a simple way of how just using these 4 variables you can control any collision, event, or automated movements
-
Refer to lim(), wall_bound(), and similar functions in /src to see how you can efficiently with the same pattern handle different types of interactions between objects
-
I have created a separate struct in my game which runs through a function and returns the boundaries that need to be calculated
This is how it looks
typedef struct s_box
{
int m_min; \\ Moving axis of the object || Start point of the Object
int m_max; \\ m_min + (w || h) || End point of the object
int m_bd; \\ Boundry of the collision object (col->w || col->h)
int bd; \\ Inverted bd
int min; \\ Inverted m_min [Constant Min]
int max; \\ Inverted m_max [Constant Max]
}t_box;
The m_ is for the axis that is moving, everything in that will be correlated. If the moving axis is X then we go for the W, similarly if Y we go for H
Inverted is the other axis which will be constant. This is quite a complicated algorithm that I came up with, try coming up with your own efficient way, that way you will be able to have full control over everything
Now comes the part that makes your game look alive, animation is fairly a easy concept but can be very tricky
Let's say your sprite has 4 textures, you load the animation to a linked list which has all the textures on individual nodes linked ending at NULL
Every time you call mlx_put_image_to_window() you just keep returning the next node's image and it keeps the animation happening
You will have to use usleep() in order to give a slight delay in between every animated frame to make the animation visible
Main render function
{
animation node temp = next_node(frame, linkedlist_sprite)
mlx_put_image_to_window(temp->image)
}
next_node function
{
static int i;
sprite temp;
temp = linkedlist_sprite
if(i >= frames)
i = 0
else
i++;
return(helperfunction(i, temp))
}
Helper function
{
while (i < frame)
{
temp = temp->next;
i++;
}
return(temp);
}
Now every time you render this in mlx_loop_hook() it will give you a new and different animation
This guide should get you ready to produce a perfectly fine game, take your time, enjoy the project, and push your creative limits !!!
You can reach out to me if you need any help at zvakil@student.42abudhabi.ae
Thank you for going through the guide, don't forget to give it a star if you liked it! and All the best with your project!