To start a simple game engine from scratch, the core modules include window management, rendering loops, input processing and basic scene structure. The first step is to initialize the window library and create an OpenGL context, and set up the graphics environment using GLFW or SDL2; the second step is to implement basic 2D rendering, write a GLSL shader and submit vertex data using VAO/VBO; the third step is to add input processing, control game behavior through key detection, and introduce time difference calculation for frame rate control; the fourth step is to build a simple scene management system, and use GameObject and component methods to uniformly manage the update and drawing of multiple objects, keeping the code clear and easy to expand.

If you want to use C to build a simple game engine from scratch, you don’t need to pursue complexity from the beginning. The core is to understand several key modules: window management, rendering loops, input processing and basic scene structure. Here are some practical steps and suggestions to help you build the easiest and available game engine.

Window creation and graphics context initialization

Before writing game logic, you must first let the program display a window and prepare the environment for drawing. Usually we use GLFW or SDL2 to create windows and handle OpenGL contexts.

The basic steps are as follows:

• Initialize window library (such as glfwInit() )
• Setting up the OpenGL version (for example, using the 3.3 core configuration file)
• Create a window and bind an OpenGL context
• Load OpenGL function pointers using glad or glew
• Enter the main loop, continuously clear the screen and exchange the buffer area

 while (!glfwWindowShouldClose(window)) {
    glClear(GL_COLOR_BUFFER_BIT);
    // The rendering code can be placed here glfwSwapBuffers(window);
    glfwPollEvents();
}

After this step is completed, you will see a black screen window. Although there is no content yet, it has laid a solid foundation for subsequent development.

Add basic 2D rendering capabilities

Once you have the window, the next step is to let it show something. You can first implement a simple rectangle drawing function, such as "sprite" or "quadrilateral".

Things to do include:

• Write Vertex Shader and Fragment Shader (GLSL)
• Compile link to shader program
• Define vertex data (position, color, texture coordinates, etc.)
• Submit data to GPU using VAO and VBO
• Call the draw command in each frame

For example: A red triangle requires only three vertices and a fragment shader that outputs red. This is the first step to verify that your rendering system is working properly.

Input processing and game loop control

The game engine must respond to the user's actions. You can obtain the keyboard and mouse status through GLFW callback function or polling method.

Common practices:

• Check the key status for each frame (such as glfwGetKey(window, GLFW_KEY_ESCAPE) )
• Map inputs to game behavior, such as pressing space jump, WASD to control movement
• Concentrate input processing into an InputManager class for easy maintenance

You can also add time difference calculations to the main loop to use for frame rate control or physical simulation time step.

The prototype of scene and object management

When you want to display multiple objects at the same time, you need some organizational structure. You don't need to start with the ECS architecture at the beginning, you can start with a simple GameObject Component.

A simple design idea:

• Each GameObject has properties such as position, rotation, and scaling.
• Each object may be attached with a SpriteRenderer or other component
• The main loop traverses all objects and calls their Update() and Render()

This way you can manage different elements together instead of a bunch of global variables.

Basically that's it. Don’t rush to add too many advanced functions. First, run these parts and then gradually expand them. For example, texture loading, collision detection, sound effect support, etc. The key is to keep the code structure clear and not pile up large frameworks from the beginning, as it will easily get stuck.

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