Q:

Antialiasing in 3D

Is it possible? Is it platform specific? Does it rely on the graphics hardware? Why does the antialiasing slider under Preferences > Appearance > Graphics do nothing? I remember seeing some post-plotting solutions years before in MathGroup, but could not find it.
Edit
System is: HP EliteBook 8440p, integrated Intel HD Graphics, running Windows 7, 64bit

A:

This needs specific support from your graphics card.  My own graphics card is very old, and does not support it, so the slider does nothing on my machine.

But the good news is that there are workarounds, and I even made an antialiasing palette (code at the end of the post -- evaluate it, pop out the palette, and if you prefer, save it using Palettes -> Install Palette...).
This is the core antialiasing function I use:
antialias[g_, n_: 3] := 
  ImageResize[Rasterize[g, "Image", ImageResolution -> n 72], Scaled[1/n]]

It simply renders a large image, and it downscales it.  The results can be better than with a better graphics card's built-in antialiasing, so it's worth a look even if you have a good graphics card.
Problems with this method:

Fonts can be blurrier than what you'd like
With a high scaling factor, it may expose bugs in your graphics driver, and show some unusual results (I had problems with opacity in more complex graphics)
Tick marks don't scale properly (I think this is a bug), so they are barely visible on the antialiased version.

This is the palette code.  Usage: select a 3D graphic and press the button.  It'll insert an antialiased image below.
Begin["AA`"];

PaletteNotebook[DynamicModule[
  {n = 3},
  Column[{
    SetterBar[
     Dynamic[n], {2 -> "2\[Times]", 3 -> "3\[Times]", 
      4 -> "4\[Times]", 6 -> "6\[Times]"}, Appearance -> "Palette"],
    Tooltip[
     Button["Antialias", antialiasSelection[SelectedNotebook[], n], 
      Appearance -> "Palette"], 
     "Antialias selected graphics using the chosen scaling factor.\nA single 2D or 3D graphics box must be selected."]
    }],
  Initialization :> (
    antialias[g_, n_Integer: 3] := 
     ImageResize[Rasterize[g, "Image", ImageResolution -> n 72], 
      Scaled[1/n]];

    antialiasSelection[doc_, n_] := Module[{selection, result},
      selection = NotebookRead[doc];
      If[MatchQ[selection, _GraphicsBox | _Graphics3DBox],
       result = 
        ToBoxes@Image[antialias[ToExpression[selection], n], 
          Magnification -> 1];
       SelectionMove[doc, After, Cell];
       NotebookWrite[doc, result],

       Beep[]
       ]
      ]
    )
  ],
 TooltipBoxOptions -> {TooltipDelay -> Automatic}, 
 WindowTitle -> "Antialiasing"
 ]

End[];

Demonstration:
 

A:

If you're running Mathematica in Linux, 3D antialiasing can be a bit tricky. Asking Wolfram support for a workaround, I got the following as an answer:

Unfortunately, anti-aliasing is not officially supported in the Mathematica front-end on Linux at this time. However, you may be able to enable it by setting the MATHEMATICA_GL_FBO environment variable to 1. Here is how to do
  this in bash:
export MATHEMATICA_GL_FBO=1
This should work on most late-model NVIDIA GPUs, assuming that you are using the proprietary NVIDIA drivers.

Note that the support also told me this is an experimental feature, but I have never experienced any problems with it, and am now using it for almost a year. I think worst case is it isn't supported by your graphics card and the workaround does nothing.
If you want to execute this command automatically when starting Mathematica, open /usr/local/bin/mathematica (or wherever you installed your executable to) and add the line at the very top. This is what my file looks like:
#!/bin/sh

# Linux antialiasing workaround, suggested by Wolfram support:
export MATHEMATICA_GL_FBO=1

#  Mathematica 8.0 Front End command file
#  Copyright 1988-2010 Wolfram Research, Inc.
#  Make certain that ${PATH} includes /usr/bin and /bin
PATH="/usr/bin:/bin:${PATH}"

...

A:

If moving the slider doesn't have any visible effect on the graphic inside the preferences dialog, then 3D antialiasing is probably not supported on your computer.  The level of support depends mainly on the graphics card and operating system.  If you tell us more details, we might be able to say more.
I also know of situations where antialiasing works for opaque scenes, but turns off when there's transparency, but that doesn't sound like that's the case here.

