Dual Textures are two textures combined to make a new looking texture. It is done by making a transparent-native texture combine over a solid-native texture, thus letting the solid show through the transparent parts of the transparent texture.

It's a real neat trick Grendel must show you, so you too can make it in your creations. Simple it be, yes, but Grendel must explain anyhow (grrr, Hastur makes Grendel angry).

Step I. The side that this method will cover is the one being pointed at with the green arrow here. This side will be refered to as "The Wall".

You don't need to prepare anything in this technique, the only thing you really need is to have the room constructed before you make the dual texture on a wall or walls.

Step II. Draw one or two lines that will create a polygon that boarders the wall you wish to put the dual texture on.

Why only one or two? Because anymore would be a waste of your time, for they get removed at the end of this method.

Step III. Fill in the polygon. Do not adjust this polygon's height in draw mode at all. Well for that matter, don't adjust anything else on it in draw mode either. This polygon will be temporary and will not be left after the method is done.

Now go to visual mode for the next steps.

Step IV. The new polygon should have white walls and defaulted textures for the floor and ceiling, like this one shown.

There is no need to change any of the textures or lights on the surfaces A, B, C and D. Leave them alone, don't mess with them because it will be a waste of time if you do.

Step V. Using capslock, pull down the ceiling marked A, ONE TICK. That is all you need, nothing more.

Pulling it down further might make the texture harder to align later.

Step VI. Now texture the two areas labeled A and B. Area A is the front side exposed after pulling down the ceiling. This is what the behind texture will be. Area B is the transparent texture on that side.

To place a transparent texture, you use the shift key and click where the side is, sometimes moving up to it to place the texture is needed.

Step VII. Go back to draw mode and now delete all the lines you created for the temporary polygon.

By deleting the lines, it will delete out the polygon also. This is wanted. Just make sure not to delete the polygon of the actual room, or delete the side that you just made this texture on.

Step VIII. Back into visual mode, make sure that what you did is correct, and make any texture alignments as you see fit.

In order to align the transparent texture, you have to do it BEFORE you delete the polygon that created it. You can align the backing texture anytime after you do this method, so you do not have to worry about the backing texture.