Different Shader Models Explained

Shaders: Past, Present and Future

by Yaroslav Lyssenko

[ 07/27/2005 | 09:02 AM ]

Bit-tech.net has issued an article about different shader models used in graphics cards. The author explains the difference between early Shader Model 1.1 and the latest Shader Model 3.0. The editorial also contains information about possible mid-term future evolution of pixel and vertex shader models, particularly about the unified shader language of the Windows Graphics Foundation 2.0 API, which will be used in the upcoming new operating system from Microsoft, dubbed WindowsVista.

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“So when are the different shader models used, and what difference do they make? The main differences between them can be summed up fairly easily. Each revision has allowed for the length of a shader - the number of separate instructions that can be executed - to be increased, allowing for increasingly complex and sophisticated effects to be created. The ways in which the programmers can be written has also improved - the 1.1 specification provides just for straight code, whilst the 2.x revisions allow for some looping to take please to repeat lines of code. The 3.0 model allows for dynamic branching along the lines of if/then statements in code. Increasingly smooth techniques for cutting the length of code have been made, allowing for speed improvements. Possibly the biggest single change between the 2.x and 3.0 specification is the addition of Vertex texture lookups in 3.0, which allows for displacement mapping to take place,” explains bit-tech.net.

• Bit-tech.net: A Bluffer’s Guide to Shader Models.