▷ Opengl: what is it and what is it for

Have you ever heard of OpenGL ? It quickly became the industry's leading real-time graphics API as it was basically the only one available on multiple platforms. Today we bring you this article in which we explain what OpenGL is and what it is for.

Index of contents

History

In the 80s developing software that was compatible with a wide range of hardware related to the graphic world was a real challenge for developers. You had to deal with very different interfaces and write specific drivers for each type of hardware, being very expensive, therefore, teams of programmers were outsourced to speed up development. Since each team worked separately on their interfaces, a lot of redundant code was produced. In 1992 SGI led the creation of the OpenGL Architecture Review Board (OpenGL ARB), a group of companies that would maintain and extend the specification in subsequent years. OpenGL evolved from IRIS GL, overcoming its hardware dependency problem by offering software emulation for those unsupported features. Thus, applications could use advanced graphics on relatively weak systems.

To understand what OpenGL is we first have to know what an API is.

Understanding OpenGL, what is an API?

An API or Application Programming Interface is a set of codes that can be used for various applications to communicate with each other. It is something that performs a task similar to the user interface in promoting interaction between person and program, only, applied only and exclusively within the software environment. It is used to connect codes or functions between different platforms, so that you can take advantage of the services of one website on another.

What is OpenGL?

It is mainly considered as an API that provides us with a great set of functions that we can use to manipulate 3D and 2D graphics and images. However, by itself it is not simply an API, but a specification, developed and maintained by the Khronos Group. It is also used for video game development, where it competes with Direct3D on the Microsoft platform.

Specifies exactly what the output of each function should be and how it should work. Since the OpenGL specification does not provide implementation details, the actual developed versions may have different implementations, as long as their results comply with the specification (and therefore are the same for the user).

Developers of OpenGL libraries are usually the manufacturers of graphics cards. Each GPU supports specific versions of this API, which are the OpenGL versions developed specifically for that graphics card. For example, when using a system from a company like Apple, they maintain the OpenGL library and, under Linux, there is a combination of graphics provider versions and adaptations for these libraries. This may mean that whenever OpenGL displays strange behavior that it shouldn't, it is very likely the fault of the graphics card manufacturers. Whenever there is an error in the implementation, it is usually resolved by updating the graphics card drivers. Those drivers include the latest versions that your GPU supports. For this reason it is always recommended to update the drivers.

OpenGL goals

The main objectives are:

• Reduce the complexity of the interface with the different graphics cards , presenting the programmer with a unique and uniform API. Hide the different capabilities of various hardware platforms , requiring that all implementations support the full set of OpenGL features (using software emulation if necessary).

OpenGL's basic operation is to accept primitive actions such as points, lines, and polygons, and convert them to pixels. This process is performed by a graphical pipeline known as the OpenGL State Machine. Most OpenGL commands issue primitive operations to graph segmentation. Until the release of version 2.0, each stage of the segmentation was executed in an established function, resulting in little configurability. As of this version, several stages are fully programmable using GLSL.

Extensions

A very interesting great feature is its extension support. Whenever a company of GPUs introduces a new technology or a new way of optimization to render 3D images , it is in an extension implemented in the drivers. If the hardware on which an application is running supports this extension, the developer can use the functionality provided by the extension to obtain more advanced or efficient graphics. In this way, a video game developer can use these new rendering techniques without having to wait for OpenGL to include the functionality in future versions, simply by checking if the graphics card supports the extension. Often, when an extension is popular or very useful, it eventually becomes part of future versions of OpenGL.

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OpenGL evolution

In March 2015, the Vulkan API was introduced as the successor to OpenGL at the Game Developers Conference. Initially known as "Next Generation OpenGL" or "glNext", the programming interface is open source and cross-platform. The difference with OpenGL is that more attention is paid to hardware during programming, which significantly increases power. Some PC games already support Vulkan, but most use DirectX. Vulkan is also developed by the Khronos Group.

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So far our article on OpenGL, hopefully you have understood what it consists of and more. Anyway, you can leave any questions in the comments.