Mordeth Map07 (while under construction) This transparent door (here used as a forcefield) can be lowered and raised without causing HOM with the right nodes builder (bsp, warm, dmapedit). Simple fixed transparent 'doors' are often used as shot-blocking windows.

SECTORS 1 : ceiling/floor x/x; 2 : ceiling/floor 128/0; 3 : ceiling/floor 1/1, different light level

LINEDEFS a: all textures removed, front middle texture transparent texture (Y=128, Y offset=+128) b : this linedefs has a reference NOT to sector 3, but to sector 2.

Using DMapEdit's internal nodesbuilder it is pretty straight-forward to create a transparent door, as shown above. The trick is to have the tracks of the door reference back to sector 2 instead of sector 3. Note that the transparent door texture is painted on the middle wall here, with an Y-offset equal to its height.

SECTORS 1 : ceiling/floor x/x; 2 : ceiling/floor 128/0; 3 : ceiling/floor 1/1 4 : ceiling/floor 127/0, tagged 900 or above 5 : ceiling/floor 1/1

LINEDEFS a: all textures removed, front middle texture transparent texture (Y=128) with an Y offset=+128, back side has a reference to sector 5 b : reference back to sector 4, these linedefs also have the lowest number compared to linedefs 'a'

It's a bit more complicated when using BSP. The same principle applies here, with some important differences. Firstly, create the situation you see above. Set all ceiling and floor heights correctly, and strip linedefs 'a' off all textures. Apply a transparent texture to the (front) middle wall of 'a' (height texture=128) with an offsett equal to its height (Y=128). Linedefs 'b' reference back to sector '4', and give this sector '4' a tag between 900 and 998... without that tag it won't work! Some editors and/or nodesbuilders remove any tags that do not have any triggers... to prevent this from happening you could assign a dummy trigger to one of the linedefs of sector '4' (eg. "lights off") and tag it to sector '4' (and make that tag a number between 900 and 998!). The back (!) side of linedefs 'a' must reference back to sector 5. Now that all sides of the door have been tagged to dummy sectors, sector 3 ceases to exist. Then make sure that linedefs 'b' have the lowest line number when compared to linedefs 'a'... if one of the linedefs 'a' has a lower number the whole effect is ruined! If you discover that this is the case, don't panic: break up linedefs 'b' by inserting two vertices, then break up linedefs 'a' by inserting two vertices. Join the inner two vertices of linedefs 'b' with the outer ones; do the same for linedefs 'a'. By doing this, you have renumbered the linedefs and 'b' should have the lowest number. Your door is now transparent.

BSP comes with an example wad that shows this effect. Note: some level editors renumber linedefs when saving, like DCK... this may well ruin your effect. Always check this!

If you made a mistake while creating this door the error probably won't be visible right away... often you'll only notice when lowering or raising the door causes a HOM to appear. Some people "solve" this by making the door ultra-fast, but if you stick to the above example you will end up with a transparent door that will not display any HOM during lowering/raising.