Cube maps
How to create a cube map (also called environmental map) of your environment using the envshot command in Doom3
Create your room
Create the room you want to have your pseudo-reflective water in. Add all the large parts, but you can leave small details (and of course the AI) out. Your room might for example look like this:
Create your images
Set the screen resolution of Doom3 to 640 x 480. If you don't do that, part of your images might be cut of and they will not fit together any more. You might have to close and reopen Doom3 for the changes to take place.
Make sure you are on full screen before you take your images. (If you don't, you can see windows task bar and it doesn't look that good ingame.) If you are in windowed mode, you can change to full screen by pressing Alt + Enter.
Open your map in Doom3 and get to the position of your water. In the console, type
envshot [prefix] [size]
[prefix] is how the images are going to be named. The size should be in powers of two. For example, your command could look like this:
envshot water_pool 512
Press enter, and you will see some flickering on the sreen while your images are created, and a message in the console will appear saying
Wrote env/water_pool_nz.tga,etc
(You might want to make a few more envshots at slightly different positions, so that you don't have to repaet the whole procedure if your images are not appropriate.)
You should now find six new images in your /env folder:
water_pool_nx.tga water_pool_ny.tga water_pool_nz.tga water_pool_px.tga water_pool_py.tga water_pool_pz.tga
looking like this: