From last thread:
If they can even handle snow properly, they can handle rain properly. It's basically the same idea, except with rain you don't get it accumulating all across the surfaces like snow, but rather a possible wet-looking effect covering surfaces. I sure hope a wet-looking surface for rain is the case.
I can see you have an understanding of the the snow shader in that, yes, they could make a rain shader via a similar method, but what nobody seems to be understanding, including you, no matter how many times I go in depth about the topic, is that we still haven't received actual information regarding HOW the snow falls, just what it looks like on the ground. There is a complete disconnect between the two unless you use particle simulations.
Specifically, the question you were answering, was that rain
falling through roofs would no longer be a problem. We can't possibly know this! Just because GI has taken some artistic license in describing a pixel shader, everybody on here has envisioned a world full of snow particles, where you can watch each one land and fall, and stick, and they all continue collecting as long as it's snowing.
To state it as plainly as possible: The system that dictates the way snow
appears in the sky and the system that dictates how snow
appears on the ground are
completely separate. To combine the two you would need an advanced physical model and a supercomputer for the physics simulation.
So, no, we have no idea if they've come up with a better precipitation system. I assume they have, but for all we know they could be reusing the rain/snow "particle" system from Oblivion in Skyrim, which was an abomination. And like I stated in the last post, they could have NEVER fixed the rain/snow problems in Oblivion because the rain/snow wasn't even in world space. Their system was like having a group of people constantly drop confetti around you as you moved, but not only that, each particle would stay with you as if it was predicting your movement.
I've probably already linked you to my in-depth post on the snow shader stuff, but here you go anyway:
http://www.gamesas.com/index.php?/topic/1158033-amazing-snow-and-enviroments/page__st__20__p__16971345#entry16971345
Again, as long as they move the actual snow particles into world space, they'll be able to physically interact in a very primitive manner at best. Each particle isn't going to stick around for eternity, they won't even collide with the terrain in any way. In world space, if everything is above the Y-position "0", for example, the snow particles will continue through *everything* they "touch" until that point and then terminate. The only way to fix overhangs and such is to have a collision plane/mesh/box that approximates the area underneath well enough to fake collisions, but it will really just terminate the snow particles in that area.