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Portability

Portability refers to the ability to render a scene, including all its hardware shaders, on a wide range of graphics hardware. This is not easy since graphics hardware from two different vendors, or even successive hardware generations from the same vendor, can vary drastically. This can be easily solved by either supporting a common subset of all hardware variants, or by requiring a different shader implementation for each variant. Neither is desirable, although it must remain possible to tailor a shader for a specific hardware or application.

mental ray is designed to separate hardware-dependencies from scene modeling as much as possible.

There are six architecture levels:

The hardware declaration describes the capabilities of the installed board. Much of this can be read directly from the board; OpenGL provides various information about which features are supported by the board, and hardware limits such as the size of shaders, size of texture memory, or the number of uniform variables. Some items remain under user control through the hardware declaration, such as symbolic register mappings and directories to search for shader declaration files.

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