The Snowfall tool
It’s just a very simple gadget aimed at simulating realistically a nice Christmas snowfall, those that happen way more often in the fairy tales books than in real life. But who cares? Dreaming, though frowned upon by serious people as little productive, is still permitted by the law.
Back to the point: this Snowfall Tool is a HUGE object, larger than the average landscape pic and more than trice as high, composed of 6 vertical layers, partially transparent, adequately spaced along with the depth (or the z-axis, as you prefer). The layer's width increases along the x-axis to ensure that the sides are properly covered even at a distance; nonetheless, a proper UV mapping keeps the density of snowflakes constant along the whole 3D field like in a real snowfall.
In this way, as the Snowfall Tool gets slowly lowered the nearest flakes look larger and move faster, and the farthest ones look smaller and slower, thus achieving an impressive degree of realism. And yes, the height of the tool grants a pretty good duration of animation (over 60 sec.).
Of course, decent camera positioning helps a lot to get the best results.
It’s a good idea to get started by looking at the scene from the top (the layers will be still clearly visible as they are sort of ‘crumpled’ in order to achieve better randomness. Place the camera before the smallest layer but not outside the ‘layer triangle’ (have a look at fig. 1) lest the left and right margins aren’t covered well enough.
![](https://www.thefantasiesattic.net/attic/tp-images/dlmanager/additional/fig1.jpg)
Now switch to ‘camera view’ and get closer with the camera (or play with the focal length) until the nearest flakes look visibly larger.
Done: you can now add a 3D scene - or just a background, according to your taste - and start planning your animation. If you consider moving the point of view during the animation you should parent the Snowfall Tool to the camera so that it keeps snowing on the whole visible scene no matter where you look; of course then in order for the snow to fall, you’ll better remember to lower the tool with respect to the camera (and not the whole set camera-tool ).
There’s an auxiliary object in the tool, START, to help you trim its initial vertical position: even if you aren’t planning to use the whole height of the tool you’ll find it useful to raise the Snowfall until START shows in front of the camera and then lower it until all the lower edges of the planes disappear down the bottom of the screen: this way you know you start with your scene fully covered and still you have the whole height of the tool to work with.
Once you’re done with START it should never show up in the field of view again (still making it invisible is an option).
A few things to remember:
• Real snow seldom (if ever) falls exactly vertically: a slight horizontal movement (maybe 1/10 or 1/20 of the vertical one) will add to your animation a nice touch of realism.
• The more keyframes you add, the smoother and more regular your snowfall will be. The critical points are the beginning and the end, where the automatic interpolation between keyframes adds a smooth unwelcome acceleration. If that is a problem consider making the clip some 20-40 frames longer and then cutting the head and the tail.
• Depending on the depth of your scene, playing with the tool’s Z-scale and Z-position allows you to modulate the size distribution of the snowflakes: too deep will get you large flakes in the foreground and only dots elsewhere, too flat will make the flakes fall all together at the same speed thus spoiling the effect. But somewhere in between, it will look excruciatingly nice.
• If possible let the hardware do the job: rendering in OpenGL or in anything working close enough to the video-card hardware may take half an hour rather than overnight. It may pay off to render this way the snowfall alone (small format, output in .png transparency) and then to superimpose (in Photoshop, using an action) each frame onto your snowless scene rendered separately in high detail: snowflakes don’t need to be sharp and detailed, quite the opposite.
Rendering directly in any video format would take a considerable part of eternity.
• If you want to make your animation cyclic you’ll need a bit of patience: the snowflakes spatial distribution is as random as it can be – the way Mother Nature makes them - thus you’ll have to look for two contiguous frames looking alike enough, take the first one and all the frames in between, and discard the rest.
Read the enclosed read-me for more info.
You may use this tool for personal and/or commercial purposes, modify it, swallow it whole without even having to credit me.
Chiron
![](https://www.thefantasiesattic.net/attic/tp-images/dlmanager/additional/snowfalltool2.gif)
2.031 Mb | Views: 81 | Downloads: 18
Last accessed May 16, 2024, 04:59:51 PM |
DarkAngel