Material Shaders (matShad; CD7FE87A)
This is not really a spec per se. But more of an idea of their purpose.
Generally speaking, they're just low level commands to the video card and assignments which the TXMT files can call on.
There're a few kinds of material shaders. These shaders can be VS(Vertex Shader), PS(Pixel Shader), just a simple material definition (just like a txmt file), TOC (Table of Contents Tree), and others. For instance, "pixelshaderwalls_PS2WallRendering" actually has definitions about the graphical structure(s) of the "wall" we see in-game. "wall_Shaders for Sims 2 walls" actually has defintions about different sorts of "walls" such as the poolwall surface, wallmask, etc...
TXMT files have lists of properties and type. Those properties and types inherit function(s) from the definitions in Material Shader.
For a particular material type, whether a material type of a txmt file can over-ride the preset values in matShad depends on whether the corresponding definition(s) in matShad has a sign "$" in front of the corresponding parameter(s). That sign is to direct the game engine to take the local value(s) from a particular txmt file.
The scripts were custom-designed by maxis and are often mostly assembly code.
Material Shader Listing
Since it's necessary for readers to read the talk/discussion board before any usage, the following linkage is linking to the talk/discussion pages directly. After reading the notices at the talk/discussion pages, one is ready to use the MatShad pages.