Brycetech: Rain in Bryce Part 2

To add to the illusion of rain, if you duplicate objects that would have rain fall on them directly you can make the shiny appearance of a wet material.
For instance in this image, I duplicated the planes and other objects that would have rain falling on them and raised them .01 Bryce units from the original position. Then I applied a glass material to the duplicate. This gave the shiny appearance to the road, trash cans, and sidewalk.
To add to the illusion of rain, give the glass material you apply to the shiny duplicates a bump map.
I personally like to use a sand basis for the bump, but use whatever you like here. Just hold down the Shift key while clicking the material button.
A visual menu will appear which will make it easier to choose a material to use for the bump map.
If the material lacks the bump channel, open up the Deep Texture Editor and add a bump channel.
Change the frequency of the glass bump to add to the appearance rain. Giving your texture higher frequencies will add to the drop effect. Reminder: Change frequency of a material by selecting the control indicated to the right.

To give some added detail to your rain, you may want to apply a 2D pict in the distance to give the feel of a distant rain or give a personalized hazy/fog effect. Thanks to Planet 3D for sharing the technique and grayscale used in one of the images on his site. Check it out!
The method you use to apply this effect is up to you. However, I made the 2D pict transparent and used it to add the feel of rain haze in the distance.
Notice in the picture below the white haze to the top right of the image. This was produced using the 2D pict above in the background.

What if you have already created a scene that you want to see it rain in? Easy to make that happen. If you are rendering through the dolly camera, then you are ready to go. If not, then you need to select the Camera to Director command. This will put the Dolly Camera in the exact position and rotation as the Director Camera.
Now view the scene from the top by selecting top view.
Notice that you can see the camera so you can use it as a guide. This gives you a reference to accurately place your rain cube. Here I placed the cube so that it encompassed the camera. The cube in this image was 1500 x 1500 x 1500 Bryce units in size.
Remember that you can use more than one cube for variety. These pictures show the camera centered to one of the cubes axis, but remember that you can offset the cubes to give a different effect. Experiment with placement, size, and frequencies to get your own effect! Here I created two cubes to give some variety in the rain.

Animating Rain is just a matter of creating several rain cubes (one on top of the other).
Then group the cubes and animate the cube from top to bottom.
Another way to animate the rain is just to think about how Bryce works. Remember that Bryce will treat each rendered image differently, so if you just create a normal animation each volumetric rain material will be rendered differently and the "shimmer" it produces can simulate the animation of the rain. If you move the camera, just be sure that the camera stays inside the cube, perhaps by linking it.