Cg (programming language)

Cg (short for Central Graphics) is a high-level shading language developed by Nvidia in close collaboration with Microsoft for programming vertex and pixel shaders. Cg is based on the C programming language and although they share the same syntax, some features of C were modified and new data types were added to make Cg more suitable for programming graphics processing units. This language is only suitable for GPU programming and is not a general programming language. The Cg compiler outputs DirectX or OpenGL shader programs. Since 2012, Cg was deprecated, with no additional development or support available.

Due to technical advances in graphics hardware, some areas of 3D graphics programming have become quite complex. To simplify the process, new features were added to graphics cards, including the ability to modify their rendering pipelines using vertex and pixel shaders.

In the beginning, vertex and pixel shaders were programmed at a very low level with only the assembly language of the graphics processing unit. Although using the assembly language gave the programmer complete control over code and flexibility, it was fairly hard to use. A portable, higher level language for programming the GPU was needed, so Cg was created to overcome these problems and make shader development easier.

Some of the benefits of using Cg over assembly are:

Cg has six basic data types. Some of them are the same as in C, while others are especially added for GPU programming. These types are:

Cg also features vector and matrix data types that are based on the basic data types, such as float3 and float4x4. Such data types are quite common when dealing with 3D graphics programming. Cg also has struct and array data types, which work in a similar way to their C equivalents.

Cg supports a wide range of operators, including the common arithmetic operators from C, the equivalent arithmetic operators for vector and matrix data types, and the common logical operators.

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