Background info: I'm assuming you know how to make textures for thief already. If you do not know how to make textures then this demo may be beyond you. Please do not email me about how to use graphic programs. You will be ignored.
A large cube that is far away represents the sky texture. It has corners and sides like any other brush. If you don't believe me then change Sky rendering mode to texture. Then type "load_sky blah" into the command box in Dromed. Make a room with lots of sky and enter it. The Jorge texture is all revealing.
The only thing different about the sky brush from a regular brush is that the sky brush looks to be the same distance away from you no matter where you are. Each one of those 6 sides can have a texture placed on it. The bottom side is usually not seen so it can be safely ignored.
Most people will not see anything below the half-mark on the n,s,e,w texture. This is because good level designs have walls that stop you from seeing all but the upper parts of those textures. Also, looking down into a sky is abnormal. Concentrate all your creative juices on the top texture and the upper part of the n,s,e,w textures.
Procedure: 1. Install this demo using thieflaoder then open miss18.mis in Dromed.
2. Note that the sky looks messed up in the Dromed 3d view. This is because it uses a different palette than regular thief textures. The palette used for sky textures is mostly blacks, grays, and whites (with a little dab of colour).
3. Go into game mode. Notice how the sky colors are corrected and the sky looks a lot better than in the 3d view. The sky's northern lights were placed a little before the top of that side's texture. Make a mental note of where this approximately is and how far down you can see if you look straight out from where you are standing.
4. Head out into any direction to the edge of the mission. Don't worry, you will not fall off the edge of the world. Look down. Note that you can see texture all the way down. This is because I texture mapped the bottom of the sky. Mapping the bottom of the sky is not necessary and can be left out but I did it anyway.
5. Back into Dromed. type "load_sky blah" in the command box. Go back into game mode. The Jorge texture allows you to see how much of each texture map you can see. Notice that the sky is a square. Think about this. You want a nice circular sky texture. You have to use square textures to make it. The centre of all the square textures will be at the right spot but the edges of the textures are going to appear compressed around the edges. This may be hard to visualize for the dimensionally impaired. The following experiment may help you if you cannot see what I mean.
Experiment: Place something round (e.g. a can) in the centre of a square box (4 books arranged in a square will also work. Visualize the player looking out from the centre of the can. The player looks at the centre of one of the sides. Mark that point on the box with a pencil. Now have the player turn 12.5 degrees to the right (12.5 degrees is 1/4 of a 90 degree turn). Make a mark on the box where he is looking now. Now have the player turn an additional 12.5 degrees to the right (he should be looking at the edge of the box now. Measure the distance from the first mark to the second mark you made. Measure the second mark to the edge of the box. The measurements are not the same even though you turned the same amount both times. Everything between the first and second marks takes the same amount of screen room as the second mark to the edge. This means the edges of the textures will be compressed when the player views them. Now think of what this means in 3d. Not only are the left-right edges compressed, but the top and bottom ones are too. It boggles the mind...
6. Ok. Here comes the part where I tell you how to put your sky textures into Dromed. Open one of the files in fam\skyhw\ in your graphics program. THE SKY USES A DIFFERENT PALETTE FOR TEXTURES THAN THE REST OF THIEF. Full.pcx holds just the palette for sky textures so don't open it unless you want to. Using the palette from the file you open make your 5 or 6 textures that you will use for the sky. They must be saved as either the dsky series (dskyn, dskys, dskye, dskyw, dskyt, dskyb) or the nsky series (similar to dsky) in the fam\skyhw folder. The texture family name is important! The last letter of the file name indicates what direction to look to see it (t=top, b=bottom, n=north, s=south, etc.). You cannot save it as some new series because Dromed only registers dsky and nsky as series.
7. Go into Editors>>Mission Parameters>>Sky rendering mode. Set it to textures.
8. In the command box type "load_sky dsky" or "load_sky nsky" depending on which series you picked earlier.
9. Place sky in your level as usual. Caution: I tried to change some textures in my level after I did this but they didn't show up until after I portalized. Dromed did not indicate that I needed to portalize. I recommend you change the sky of your level as the last thing you do.
by Zail, copied from Dromed Central DB