Because this is my first foray in the field (myfirst.vfx, as it were), and because I'm attacking problems that have largely been solved already, most of my peices have started out from tutorials. As I do hope to gain a solid understanding of the techniques, I'm hoping to expand and customize them.
The first one I've done is a tornado, based on Pete Draper's "Assisted Twister" http://www.computerarts.co.uk/tutorials/premium_content/3d__and__animation/assisted_twister
The original version of the background photo is by Matthew Hull, and used under a Morguefiles license ( http://www.morguefile.com/archive/?display=98566 )
I have ajdusted the background in Photoshop, tweaked the twister materials, and added a wave effect, to make the tornado less static. I suspect it could still use some work-- I'm thinking about scaling the radius of the funnel and vortex, and perhaps toning down the wave.
My second effort was a modification of Arxwyn's 3d Studio Max Rain Tutorial http://www.tutorialized.com/view/tutorial/Rain-Tutorial-for-3D-Studio-Max-PFlow/22408
Using a cleaned up version of a background photo produced by the National Oceanic and Atmospheric Administration (and thus in the public domain : http://www.photolib.noaa.gov/htmls/wea02159.htm)
I added variability, motion blur and depth effects to the rain. Arxwyn's tutorial didn't specify materials, so most of my work went into getting those right-- a more experienced artist would have done proper ripple animations baked onto a texture. I settled for low opacity medium-spec images on the rain and the impact droplets. I was disappointed because I wanted both the spec and a very light subtractive transparency on the droplets themselves, but the two effects appear to be incompatible. The small puddles use a particle age map for their specularity levels, with the starting state being white, end state being black, and the mid-state being a greyscale radial gradiant ramp that looks similar to a ripple impact.
For my snow scene, I started from rpadc2002's "Making a Winter Scene" tutorial: http://www.enjoycg.com/forums/enjoycg-tutorials/2764-making-winter-scene-tutorial.html -- that said, it was hardly necessary. I was intimidated at first because it uses the non-pflow particle setups, but the blizzard primative really does just what it says, so it was mostly a non-issue. I added some post process effects (depth of field), but there wasn't a lot to add in a technical sense. That meant I was free to do a little expressive art here, playing with adding secondary emitters and space warps, to give it more of a "snowstorm" effect rather than a mere snowfall.
The base image is a modified version of "White Shit" by Uncle Ariel, released under an attribution license: http://www.flickr.com/photos/afgeneral/390892712/sizes/o/
For the Lightning I referred to Arxwn's tutorial on the subject as a starting place.
http://www.phoenixbit.com/site/tutorials.asp?view=R3JhcGhpY3MvM0QgU3R1ZGlvIE1heC9zdG9ybQ I then rejiggered all the parameters and tossed it into video post. While the basic approach seems solid, the big flaw with what Arxwn was doing is that the lightning bolts remained the same size at all points-- where real lightning appears to have a thicker trunk and tapering branches. I suspect an actually elegant solution to this issue requires slightly more scripting than I now posess; however, I was able to obtain satisfactory results by applying a scale operator in the main part of the pflow loop, such that each particle grew to 105% in each pass. This creates a "growing" bolt as a side-effect, but I'm not displeased with that.
What I *am* displeased with is that this approach is highly difficult to scale for larger sizes. Because each particle is spherical, if I scale it much larger than it is at present, the particle shape becomes evident. Thus, some relatively hair-thin lightning:
Next: FIRE (part one).
[EDIT: Ripping out the mediafire links and replacing them with YouTube ones, now that the compression issues are resolved.]