Unity (C/C++ Scripting)

What it is

Unity is a cross-platform game engine that allows developers to create 2D, 3D, VR, and AR games. While Unity primarily uses C#, low-level plugins and performance-critical components can be developed using C or C++ for integration via Unity's Native Plugin Interface.

Unity allows you to write C# scripts for game logic, while C/C++ can be used for native plugins that are called from Unity scripts. These plugins provide performance-critical functions, access to platform APIs, or custom rendering/physics systems.

Installation

Download and install Unity Hub from https://unity.com/

Getting started

The smallest useful thing you can do with it, and what each part means.

Creating a simple C plugin

c

123456// myplugin.c
#include <stdio.h>

extern "C" void HelloPlugin() {
    printf("Hello from C plugin!\n");
}

Defines a simple C function that prints a message. The `extern "C"` is needed to avoid name mangling for C++ compilers.

Calling C plugin from Unity C#

c

1234567891011using System.Runtime.InteropServices;
using UnityEngine;

public class PluginTest : MonoBehaviour {
    [DllImport("myplugin")]
    private static extern void HelloPlugin();

    void Start() {
        HelloPlugin();
    }
}

Shows how to import and call a C function from Unity using DllImport in a C# script.

Advanced usage

Where the library earns its place over a simpler alternative.

Passing data to C plugin

c

1234// myplugin.c
extern "C" void AddNumbers(int a, int b, int* result) {
    *result = a + b;
}

Demonstrates passing values and pointers between Unity C# and a C plugin.

Using C++ for complex logic

c

12345// myplugin.cpp
#include <cmath>
extern "C" float ComputeDistance(float x1, float y1, float x2, float y2) {
    return sqrtf((x2 - x1)*(x2 - x1) + (y2 - y1)*(y2 - y1));
}

Shows a C++ plugin function performing calculations callable from Unity.

Integration with Unity physics

c

// Native physics calculations in C/C++ can be exposed as plugin functions
// Then invoked from Unity scripts for performance-critical tasks.

Use C/C++ for heavy physics, AI, or rendering tasks that require native speed.

Errors and fixes

The failures you are most likely to hit, and what actually resolves them.

DllNotFoundException: Ensure the plugin binary is in the correct folder (Assets/Plugins) and named correctly for the platform.
EntryPointNotFoundException: Check the function names in the C/C++ plugin and match them in DllImport attributes.
Segmentation fault / Access violation: Ensure proper memory management and pointer usage in C/C++ code. Avoid invalid dereferencing.

Best practices

Use C/C++ plugins only for performance-critical code.
Keep plugin APIs simple and well-documented for Unity integration.
Manage memory carefully to prevent leaks or crashes.
Ensure platform-specific binaries are compiled for all target platforms (Windows, Mac, iOS, Android).
Use Unity Profiler to identify areas where native plugins provide real performance gains.

Background

Why it exists, and what it was reacting to.

Unity was developed by Unity Technologies in 2005 to provide an accessible yet powerful game engine. For high-performance needs, developers use C/C++ plugins to interact with Unity, enabling optimized physics, graphics, AI, or platform-specific integrations.

Related libraries

Others in UI & Graphics for C.

Xlib

SDL2

GTK

libpng

libjpeg-turbo

OpenAL