What are Shaders?

I've heard the term "Shader" many times and I havent put too many attention to it. But on the latest Steam Update, Valve mentions the capacity for us to create our own shaders. So if anyone can answer me, What are Shaders?

AHHHRRRGG!! I wrote a realy good and long reply to this post!!! AND
THEN SOURCE SDK UPDATED, LOST GAMEINFO.TXT AND OPENED A HELP PAGE HERE
ABOUT IT AND MY REPLY WHERE LOST!!!!!!! GHAAAARRRRR!!!!!!!!

<div style="text-align: right;">ha.a.ahah.hah

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brett, you are not being helpful.. most of us have had this happen a few times, and it loses its uniqueness after the first 1/2 dozen or so.

Shaders are unique ways of representing textures?

So proper cellshade can be done?

Take a look at it this way: you put textures on your brushes, but
want to add an effect. The floor has to reflect certain things, or it
has to look wet and slippery ... that's where shaders come in. They add
certain effects to textures.

<div class="quote"><div class="quotetitle">

quote:</div><div class="quotetext"> A procedural plug-in, loaded into the mental ray
rendering software in the form of a shader library, that defines the
surfaces of objects in a certain way. Originally, shaders computed only
surface shading, but the term stuck as new types of shaders were
invented that had nothing to do with shading. Shaders are grouped as
the following types: contour, displacement, environment, lens, light,
light photon, output, photon, shadow, surface, texture, volume, and
volume photon.</div></div>


<div class="quote"><div class="quotetitle">? quote:</div><div class="quotetext"> A shader defines the final surface properties of an
object. For example, a shader can define the color, reflectivity, and
transluscency of a surface.

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oooh evamod will have a field day with that = p propper cell shaders wow ^_^ ! sounds like fun !

are they still working on it?

I get it. It's like when you have a texture for clear glass and one for darkened glass, both are trnaslucent but the dark glass reflects more than the clear one. In the past, on the Quake engine they used to simulate the effect of water, sludge and lava using movement on the texture.

Thanks for the info Forceflow.

Source SDK FAQ says shaders define the equations used to work out the colour of each pixel. So, this is a coding thing... but that allows for some cool modding capabilities, like cel shading, and... other cool stuff i cant think of at the moment.