Originally, I was intending to create a simple still image of a miniature tree in a glass case on a desk. Then I thought it would be more interesting to show the tree in autumn, with the leaves falling onto the desk. I used Cinema 4D's Thinking Particles to grow the leaves and then have them fall in a slight turbulent breeze, and it looked pretty cool in the still, so then I decided to animate the entire growth/change color/fall sequence. Of course, once I had Spring, Summer and Fall, I had to finish up with Winter, so I added a brief snowstorm.
At this point, the original environment no longer seemed to fit, so I changed it to something a bit more "Mysty", featuring a rough stone pot on a stone table within a dim stone chamber. To add a bit of motion to the whole thing, I then rotated the camera once around the tree as the seasons passed, 1 degree per frame. The end result (after a whole lot of fiddling with the textures, lights and timing) is an entire year passing in 24 seconds (360 frames at 15 frames per second).
Everything was created, textured and rendered in Cinema 4D 9.1, with the exception of the tree itself, which was built with Xfrog. The complete animation took just over 14 hours to render.
This is the result. The picture here shows 4 frames from the animation (using a stationary camera rather than the rotating one in order to show the same angle each time). You can see the full animation here (you may have to right-click and "Save as"):
http://www.imaginerie.com/c4d/Images/Seasons.avi is a 35.5 Mb AVI, DiVX 5 encoded, complete with a theme-appropriate soundtrack; see if you can correctly identify it ;-)
http://www.imaginerie.com/c4d/Images/Seasons12.avi is a 3.07 Mb AVI, DiVX 5 encoded. It's the same animation, but without the soundtrack, for those of you on dial-up.