Ok here we go. 
First thing. The waterfall is nothing more than a sprite movie shader. Like the famous fire shader we’ve all seen before. Drakir’s waterfall is exactly this form of shader. I very strongly suggest that you create a testroom map to make production of this element easier and faster. Ie a 1000 x1000 x 500 high blank box room called testroom would be a good idea. My suggestion only.
Creating the images for your animation waterfall:
:eek2: LOCATION OF IMAGES:
Example:C:\Program Files\Wolfenstein - Enemy Territory\etmain\sprites\ —would be your waterfall animation frames need to reside while in development stage. When your done, you HAVE to have this folder included in your pk3 file compilation. Don’t do it and you’ll get the ugly texture in your map. 
This folder probably won’t originally exist in your etmain directory, so make it.
:eek2: BASIC RULES OF DEVELOPMENT:
Rule 1 : Your images cannot not be bigger 512 x 512 pixels at 72dpi. Targa’s need to be 32bit to play it safe. Jpg’s are fine too. Obey the rules of Quake3 engine here ie 256x256, 128x128 , get it?
Rule 2: You should restrict the length of your animation to not more than 15 frames. Don’t know why this is, but, well, anyways, obey this rule to be safe.
“What is a frame? A frame is a single image that is part of a series of images that suggest movement. Like in filmmaking.
Rule 3: The bigger the frame image size the more likely you should limit the animation length less than 15 frames.
:eek2: THE FRAME IMAGES
Develop your frame images in your favorite Image editing program. Ie Photoshop. Remember that the Quake 3 engine likes images a little on the dark side.
NOTE: Name your images in sequence ie(waterfall001.jpg,waterfall002.jpg) This will avoid the nightmare of figuring out the films proper sequence. In your image editing software it is important to construct in reverse of the anticipated forward movement of the animation to ensure proper looping. Don’t make very large movements between the image making process or the movie will appear choppy.
Save your images directly into the sprites directory to avoid missing a frame later. Just a suggestion.
:eek2: THE SHADER FILE.
Ok, your done making your frames. Now its time to script this baby up.
What is a shader file? It’s a text file that has a .shader extension that defines attributes for a specific texture that you created. It gives the texture guts.
Where should it reside? In your scripts directory. This allows Radiant to “see� this shader during editing. As a note, usually the first frame is good reference for listing the shader file, Or make the name unique from the actual frames themselves.
:banghead: IMPORTANT NOTE: In the script directory your going to see a file called “shaderlist.txt�. The name of your shader file needs to be included in the list. Don’t do it and ,well, you’ll find out.
:eek: THE FILE ITSELF – Example
textures/t_outreach/try3dwaterfall
{
q3map_surfacelight 0
deformVertexes wave 160 sin 0 10 0 .5
cull twosided
nofog
surfaceparm nomarks
surfaceparm nonsolid
surfaceparm water
tesssize 384
waterfogvars ( 0.1 0.1 0.1 ) 128
qer_editorimage sprites/t_outreach/try3dw.jpg
{
animmap 35 sprites/t_outreach/try3dw001.jpg sprites/t_outreach/try3dw002.jpg sprites/t_outreach/try3dw003.jpg sprites/t_outreach/try3dw004.jpg sprites/t_outreach/try3dw005.jpg sprites/t_outreach/try3dw006.jpg sprites/t_outreach/try3dw006.jpg sprites/t_outreach/try3dw007.jpg sprites/t_outreach/try3dw008.jpg
blendFunc add
}
}
The above is squished together and should only be used as a reference.Can A regular experienced forum poster fix this for me?
Notice the listing of the images above? That’s how it should look, except, ofcourse, your nomenclature would be there. Now, how fast it animates is dictated where you see “animap�. The number after that tells the engine how fast to render this sprite movie. Experiment with this number to get the speed you want. Notice how it constantly refers to the same directory for each frame? Make absolutely sure this remains the same, or else it won’t work at all.
This particular waterfall has deformations taking place that makes it look like its wavy (deformVertexes) Delete this line if you don’t want wave movement. Don’t leave a gap between lines if you do this. Otherwise you can adjust this by changing the big number. Be careful, though, this can cause some hilarious results! Experimentation is the order of the day! A more detailed explanation of the other variables can be found in the Radiant reference manual.
For waterfalls its critical that it be recognized as a water element and that it is a nonsolid. Cull two sided means that it can be seen from both sides.
:eek2: DOING IT IN RADIANT:
Load up your test map. Create a simple or deformed mesh. These are great for waterfalls. Design it the way you want it to look. Load up your shader list and find your shader files name. Remember your name being put in the shaderlist text file? If you did it right, it will tell you it loaded up the shaders properly in the command line at the bottom of the radiant editor. Find the texture that you made and assign it to the mesh or brush and walla! You have a waterfall. It will probably appear very dark, ignore this, because it wont after compilation.
Now load up your test map and see the results. Adjust as necessary to get the waterfall you want.
PUTTING IT ALL TOGTHER:
You must have:
1.Sprites folder with ALL the images to complete the animation.
2.Yourshadername.shader file placed in the scripts folder.
These two things MUST be included in your pk3 file!
Do these two things correctly, and your in the movie business baby!
To see what sprite movies can do, check out my humble map Operation Outreach at:
http://home.comcast.net/~imhoptep/
Note: This is my humble attempt to 101 the art of making sprite movies for ET. If I have missed something important, please post it immediately. Please make sure that what you post is correct. Nothing pisses people off more than misleading information. Intentional of Not. People are funny that way.
Thanks! And Happy Mapping!
Try3d
P.S. Special thanks goes to Drakir and other fine mappers that release their source files so that other aspiring mappers can figure this crazy stuff out!
Happy Halloween!