Snow And Rain
The PC doesn’t know what to do with snow, a weather phenomenon simulated with copied flakes. As the snow is just an optical effect, it doesn’t remain lying on the ground, the levels never rise, and it can never melt. When PC hardware will be able to handle masses of particle snow is anybody’s guess. This effect is going to require considerable calculation by the physics units. The representation of landscapes and icy structures, on the other hand, are very advanced, and snowy tress and rocks look very realistic (and downright chilly).
Rain is also a major problem, as the drops are just an optical effect. If you stand under a bridge in Oblivion, you will still see the rain falling despite the huge masses of stones protecting your head. Stalker has come along a little further. The 3D engine lets you enter houses without reloading, and the roofs are real objects, so the rain only enters through holes. It isn’t really water, of course, so objects do remain dry and fires continue to burn (and you also can’t catch a cold).
Stalker: Clear Sky has achieved the first real improvement here. When set to maximum graphics quality, wet surface textures have a special effect. When rain will be made up of real particles is anybody’s guess. There are great demos out there with water effects, but the current physics units probably don’t have enough computing power for an entire 3D game.
The next stage is to introduce improved rain that makes characters and objects wet, and beads up and drips off them just like it does in the movies. This optical physics effect was announced for Hellgate London, but disappeared back into the pockets of the developers.
It is possible that the fact that PhysX was purchased by Nvidia and Havok by Intel got in the way of things. As Havok is shared with AMD, both graphics manufacturers have their own technology and license, which enables physics effects on the PC. Hopefully it will be possible to quickly agree on a standard before adapted games are released onto the market that are only capable of displaying the full range of effects with either AMD or Nvidia (but not both). According to rumors, Nvidia has now offered PhysX to AMD, which is going to work on driver support.