Ok first of all for people who dont really know what a rendering engin is. It is a piece of software not unlike the one used in Maya to render our small animated movie clips. However rendering engins at thier core are mostly proprietary software developed by and for the gaming industry. Good example of these are the "unreal" engin and the "crytech" engin used to make some of the most visually stunning games to date such as unreal tornament and crisis ( the benchmark for most gamers in graphics. )
another thing you may not have known is these engins dont simply render how the model will look underlighting but also how it will be effected by the environment around it. This is becuase these particular rendering engins also have other programs that run within it. One of these pragrams is refered to as a PHYSICS ENGIN ( this is what the rest of the post will be about ).
Physics engins deal with partical and object based animations. They are able to simulate gravitational values for exmaple you can set your animated world to be a heavy gravity world in which light object move as if they are heavy or vice versa. They also deal in vector collisions which is an object traveling at speed and then hitting another object. A perfect example of this is rain.
For the most part physics engins are math ( A FREAKIN LOT OF IT ) and programming. However they have an imense impact in animation as they can be used to recreate environmental effects with such accuracy they are almost indistinguishable from the real thing. FOr the most part though physics engins wernt perfect. Their power is limited to that of the machiene they are used on also they generally have a set amount of objects they can control ( E.g smoke is made up of millions of particals each one seperate from the other, to hand animated lifelike smoke is almsot imposible) Also the limit on the objects means there is a limit on how realistic it can look reguarless of the artists abiolities.
If i have learned anything about technology its this "given unlimited time and funds, eventually you will end up with ever more complex and intuitive inventions" in others words we only go forward never backward. to that end an new physics engin has been created ( currently without a name ) which has completly blown my mind! insane partical numbers and realistics interactive physics means you can create some of the most realistic material simulations to date.
why is this relavant to me? ( you he he) Well if you watch the video below you will quickly see how amazing something like this can be in your back pocket. I stumbled on this while trying to find a way to acuratly animate water without neededing to actually animate it. ( get the software to do it for me ).