Transform and lighting

Transform, clipping, and lighting (T&L or sometimes TCL) is a term used in computer graphics.

Transformation is the task of producing a two-dimensional view of a three-dimensional scene. Clipping means only drawing the parts of the scene that will be present in the picture after rendering is completed. Lighting is the task of altering the colour of the various surfaces of the scene on the basis of lighting information.

Hardware T&L had been used by arcade game system boards since 1993, and by home video game consoles since the Nintendo 64's Reality Coprocessor GPU in 1996.Personal computers implemented T&L in software until 1999, as it was believed faster CPUs would be able to keep pace with demands for ever more realistic rendering. However, 3D computer games of the time were producing increasingly complex scenes and detailed lighting effects much faster than the increase of CPU processing power.

Nvidia's GeForce 256 was released in late 1999 and introduced hardware support for T&L to the consumer PC graphics card market. It had faster vertex processing not only due to the T&L hardware, but also because of a cache that avoided having to process the same vertex twice in certain situations. While DirectX 7.0 (particularly Direct3D 7) was the first release of that API to support hardware T&L, OpenGL had supported it much longer and was typically the purview of older professionally oriented 3D accelerators which were designed for computer-aided design (CAD) instead of games.

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