you mean makes it look amazing and clean? instead of blocky strips of shadowing.
Setting iShadowMaskQuarter to 0 messes up interior lighting/shadows. I have pretty nice and clean shadows now with that set to 4. I'm experimenting with other values, but 4 looks pretty good to me. Seems like using the launcher to start the game resets that value to 4 anyway (as well as some other values... use tesv.exe instead).
iShadowMaskQuarter=0
iShadowMaskQuarter=4
Here's my shadow settings atm (SkyrimPrefs.ini):
iBlurDeferredShadowMask=4 (blurs edges of shadows)
fInteriorShadowDistance=3000.0000
fShadowDistance=3000.0000 (lower number = less blocky shadows, but also = less draw distance)
iShadowMapResolution=4096
iShadowMapResolutionSecondary=4096
iShadowMapResolutionPrimary=4096 (also in Skyrim.ini)
iShadowSplitCount=2
fShadowBiasScale=0.1500
iShadowMaskQuarter=4 (still experimenting with other values)
iShadowMode=4
iShadowFilter=4
bTreesReceiveShadows=1
bDrawLandShadows=1
bShadowMaskZPrepass=0
The settings below (put in Skyrim.ini) have helped the game run a lot smoother, and also increase distant detail. Anyone familiar with tweaking other Bethesda games will recognise them...
[General]
uInterior Cell Buffer=32
uExterior Cell Buffer=128
uGridsToLoad=7
iPreloadSizeLimit=209715200 (careful messing with this one)
Note about uGridsToLoad... it seems that once you set it to a number changing it to a lower number after saving can cause stability issues. I've had crashes, and so have many other people. I'm not totally sure if it's this setting causing it, but it could very well be. Right now I have it set to 7 and have not had any problems. If you find 7 causes too much lag (which it doesn't for me) and you've already saved your game you may have to either live with it or set it lower and restart your game.