Using GIMP 2.8.4, the latest. My image is 3000x3000 and prints at 100 dpi.

Quote Originally Posted by Jacktannery View Post
It's easy! Make a new (transparent) layer, FILTER>RENDER>CLOUDS>FOG, change colour to something good like very pale grey, then press ok. Then use a layer mask to remove it from the walls, and change the opacity. The crucial thing with fog is that you need to light and shadow it. To do this, copy the fog layer and apply its layer mask and make this layer invisible. Then make a new 'lighting' layer and with a big fuzzy brush messily draw very pale yellow (eg) overlay highlights over some of your fog. Then add layer mask, and make that mask the copied and applied fog layer. Then do the same for some shadows. Its important to give fog depth otherwise it looks crap.
Okay. I made a fog layer and selected where I wanted the fog and clicked FILTER>RENDER>CLOUDS>FOG. It looked like the floor noise, so I removed the floor noise to avoid confusion.

Then, I duplicated that layer and made the first one invisible by removing the little eye beside it.

Then, on the duplicate, called Fog Light with a mode set to Lighten Only, I scribbled haphazardly not knowing where I should with my mouse using the Paintbrush Tool at 100 px. The color was fffdcc, a very pale yellow. It looked... Well, like I just described. A bunch of yellow lines everywhere.

I didn't bother to do the same with black because obviously, I'm not doing the right thing at all.

Here is the update: http://img6.imageshack.us/img6/7528/shadowyrm8.jpg

Yes, it looks ridiculous, but I wanted to illustrate how little I understand the instructions given.

Also, the default filter needs some help. The fog should be thicker in the low spots. So, I'll have to do something about that. This was just a quick test. The mist is coming from the room with the water (bottom row, very middle).

Further advice would be greatly appreciated, if anyone has the patience of Job to help such a hopeless newbie.