OpenGL and DirectX are two graphics APIs primarily used in game development. They are developed to act as a bridge between the graphics hardware and software. Both of them provide standardized methods to display 2D and 3D graphics on-screen and are fundamental to game development. However, beyond games, only OpenGL targets the professional graphics market. This OpenGL vs. DirectX comparison should give you an idea of which of these two tools is best for you.
OpenGL vs. DirectX: Side-By-Side Comparison
The table below compares the main specs and features between DirectX and OpenGL:
| Specification | OpenGL | DirectX |
|---|---|---|
| Developer | Khronos | Microsoft |
| Operating systems | Windows, Linux, macOS, | Windows, Dreamcast, Xbox |
| API scope | 2D and 3D graphics | Graphics, audio, networking, etc. |
| Supported file format | .obj, .3ds | .c4d, .max, .3ds, .3dm, .obj, .fbx, .ma, etc. |
| Engine compatibility | Unity, Unreal | Unity, Unreal |
| Updates | Yearly | Yearly |
OpenGL vs. DirectX: What’s the Difference
Today’s web and mobile gamers expect a seamless experience that combines great content with responsiveness. There is much debate between developers regarding which API between DirectX and OpenGL is smoother and more efficient, with most opinions leaning towards the latter for the simple reason that it’s cross-platform. However, the only way to find out which is actually best is through testing each API’s performance, resource management, and ease of use.
Performance
OpenGL and DirectX have similar capabilities and rely on the same graphics pipelines to build complex graphics primitives. These pipelines, called vertices, store coordinates and other important information, but the way each API uses these vertices to develop 2D and 3D graphics is different.
They also use different vertex libraries, meaning that each API also responds differently to the developer’s commands. For instance, OpenGL’s cache geometry consists of display lists, whereas DirectX’s consists of vertex buffers. OpenGL can produce system emulations without present hardware, while DirectX lets the app determine whether hardware presence is necessary.
This leads to differences in performance. Developers typically use Unity Platformer and Unity Carting to test the performance of these two APIs, thanks to their compatibility with Unity.
Unity Platformer is a free 2D microgame template that allows developers to create simple Boulder Dash-style games. In a simple player-and-enemy setup, DirectX can generate an average frame rate of about 770 fps. Meanwhile, OpenGL’s average frame rate is around 515 fps. Both results are playable, but the difference is dramatic and in favor of DirectX.
The same seems to be true when testing the 3D performance. This can be achieved with Unity Carting, another free microgame template that allows users to build a simple racing game. As expected, the performance drops compared to 2D for both APIs, but DirectX can still outperform OpenGL with around 365 fps – OpenGL only generates about 280 fps.
So, even if people claim OpenGL is best, DirectX might be better – especially for developers creating games for Xbox and Windows platforms. Sure, since DirectX isn’t a cross-platform API, OpenGL is the obvious choice for all other operating systems.
Hardware Management
Another major difference between OpenGL and DirectX is the way each API manages its hardware resources. That’s because DirectX was not designed to allocate hardware resources initially. Microsoft only included this possibility in DirectX 7 and above, mainly to provide hardware acceleration support and improve responsiveness for more elaborate games.
However, this API still allows developers to disable automatic hardware resource management. In this way, you can allocate resources as you need them, improving efficiency when developing simple graphics.
With OpenGL, developers don’t have to worry about hardware resource management. The API optimizes resources automatically to ensure the ultimate gaming experience. However, resource allocation can’t be micromanaged if necessary. This automatic process can also make tasks much harder for developers initially. Yet, the process often becomes smoother once you’re familiar with the interface.
Ease of Use
API ease of use used to be a crucial factor when deciding on one over the other. Today, however, most APIs run behind engines like Unreal or Unity. Since both engines are compatible with OpenGL and DirectX alike, all it takes is a click of a button to swap from one API to another.
Things change if you’re developing a game from scratch and don’t want to use an engine. In this case, OpenGL is somewhat easier to use. Alongside hardware resource management, this API only handles graphics, a factor that makes it simpler by nature. OpenGL also allows cross-platform functionality, which is another point in its favor.
Whether or not you decide to use an engine, both DirectX and OpenGL come with detailed documentation that can make development much easier. In addition to regularly updated documentation and guides, both APIs have helpful developer communities that can smooth down the learning curve.
Purpose
The actual functions and effects that you can achieve with these APIs also differ. OpenGL enables developers to use two-sided lighting, define parametric curves and surfaces, add volume textures and stereo rendering, and more. DirectX can’t perform any of these functions through Direct3D, but other APIs in the suite – such as DirectSound, DirectPlay, or DirectDraw – can take care of them.
The fact that DirectX is actually an API suite rather than a standalone program is the first clue that Microsoft’s brainchild is more than just a graphics API. In fact, it also supports sound, music, networking, multimedia, and input. This is a major difference between DirectX and OpenGL, which is strictly a graphics API.
Platform Compatibility
Another major difference is that DirectX is developed specifically for Windows, Dreamcast, and Xbox, which are all Microsoft products. However, OpenGL is a cross-platform API that works on various operating systems and that can pair with various hardware types, such as Nvidia or AMD graphics cards.
OpenGL vs. DirectX: 6 Must-Know Facts
- DirectX is an API suite developed for Microsoft operating systems and gaming consoles (Windows, Dreamcast, and Xbox). OpenGL is a cross-platform API suitable for Windows, Linux, macOS, other operating systems, and various consoles.
- Both DirectX and OpenGL are compatible with engines like Unity and Unreal.
- OpenGL featured a hardware accelerator and provided hardware resource management from the start. This option only became available on DirectX 7 and above.
- DirectX suite addresses game performance directly. OpenGL is targeted at graphics professionals first and game developers after.
- OpenGL is often believed to be the fastest of the two, but game development tests showed that DirectX outperforms the former.
- OpenGL can only be used to create 2D or 3D graphics. DirectX includes functionalities that give supported features for sounds, music, input from joysticks or keyboards, and more.
OpenGL vs. DirectX: Which One Is Better? Which One Should You Use?
DirectX and OpenGL are similar APIs used by game developers to create fast and responsive applications. They both use vertices but were initially created for different purposes. Due to this reason, DirectX is usually the best choice for developers creating games for Windows or Xbox consoles.
The DirectX suite includes a variety of APIs you can use to develop 2D and 3D graphics, then link those graphics to sounds, music, joystick, keyboard, mouse movements, and more. This API is compatible with Unity and Unreal and generates fast and responsive games.
OpenGL, however, is the best choice if you’re a graphics professional only interested in developing 2D or 3D graphics, regardless of the platform. It is also the obvious choice for those who want to develop games for any platform other than Windows or Xbox. OpenGL is compatible with a variety of operating systems and GPU types, and it can also be integrated within Unity or Unreal for effortless game development.
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