What the Shader Model?!? You aint in Kansas anymore...

[jujubee]

I do not comprehend shader models. I've struggled with the concept for quite some time in ignorant bliss but just went about my day and hit render. Perhaps it's just the language programmers ues to suppress the masses.

I think I know the basic concept- newer models equals better performance and graphics. I think they are used in real-time graphics and some allow for new effects (such as better? displacement.) But it's all like the wizard behind the curtain in the Wizard of Oz. Does it effect all Max users or is it primarily animators or game developers?

Different instructions? 96 levels? Multipass? Ack.

Vertex Shader.
Pixel Shader.
Misnomer?

I think of shadows on a pixel or a vertex and I think to myself- how the hell can you see shadows on a pixel/vertex? Max only zooms in so far. You gotta be really near-sighted or have an electron microscope handy to perceive this effect...

Please- real-world explanation please.

[mike.edel]

shading models differ from vertex/pixel shaders afaik

vertex/pixel shaders (currently) are for realtime stuff only

vertex shaders are some some kind of procedural description (shader) to describe how vertices of a realtime model should be tranlated in space (possibly over time)
for example, current games do their facial animation using a vertex shader that moves the facial features according to an input animation sequence
the huge advantage of vertex shaders is that they can be executed in graphics hardware - making the animation of possibly complex models way faster (some years ago - before vertex shaders - there was virtually no vertex animation in games, just transformations of the seperate body parts)
you could easily do the same computation in cpu (software), but that's slower

pixel shaders change the color value of a rendered pixel
for example you could have the shader blend the pixel value of a head up display over the realtime scene to simulate looking through the HUD.
Or you could change the color of an object depending on the angle of its face normals (this is done in toon shading - areas with normals facing 90° towards the screen are the borders of the object and are painted black - resulting in an outline)
pixel shaders are quite close to max's materials, they allow you to blend several colors coming from different sources into one and apply this to a rendered pixel. they are (more or less always have to) be executed in graphics hardware.

shader models are different mathematical approaches to render materials in software. they are usually optimized towards a special type or group of materials.
flat shading is one of the simplest models - there only is one color per (tri)face of the objects
gouraud shading interpolates the face color between its surrounding colors (using the normals of the triangles vertices) - lets hope i got this right, but thats the way i remember it. gouraud shading is also called smooth shading.
both smooth and flat shading originally dont render highlights - they only take into account diffuse and ambient components of the light.
the next model is the phong shading- it calculates the shading for every point of a face by interpolating the surrounding normals like smooth shading and then calculating the point's relation to the light source to add a highlight
blinn and cook shading are variations of this idea
those models usually only deal with the light that hits objects and gets reflected from them, thats why they are called bidirectional reflectance distribution function (BRDF).

there are other models:
for calculating sub-surface-scattering (rendering skin/milk/marble)
http://graphics.stanford.edu/~henrik/papers/bssrdf/
this model also takes into account the light that gets scattered (broken up) inside the model - hence the term bidirectional surface scattering distribution function
(BSSRDF).
Figure 1 in this paper is quite clear in illustrating what's the difference between both models i think. (not that I understand any of the math behind it...)

other shading models would give you Anisotropic highlights (brushed metal) or different ways to influence the shading calculation

most of the time i tend to stick to the blinn model, as it gives me a lot of control...
bssrdf would be nice for sss effects, it already has been implemented at ILM and Weta digital (probably using renderman shaders)

Hope that was at least half correct and didnt confuse you even more...

cya,

Mike