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Sliding Doors In Boom

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This tutorial is specific to the BOOMQTEX resource, but could be adapted to any Boom map.

The basic principles are based on a 1998 map by Nicholai Main, that demostrates sliding doors in Boom format:


We'll start with a simple room with a doorway:

We'll add some definition with a door frame, and we'll model how the door would look fully open by building bits of it into the frame:

Additionally we gradient the lighting a bit to obscure the door's hollow interior:

Now we'll add the real 'physical' door that sits inside the frame:

In BOOMQTEX a medieval door has to be fast to play the correct SFX, and the speed helps to obscure that the door isn't a solid polydoor:

Now we add 2 dummy sectors. The one on the right is joined to the 'real' door sector and will be used to the drive the horizontal motion of the fake sliding mid texture doors later. The left dummy sector has the same floor and ceiling heights as the open door frame, and is used to render the 'real' door invisible.

A quick test confirms that yes, we do have a functional invisble door:

Now we add line actions to the linked dummy sector, that are parallel to the motion of the sliding door. When the real door changes the height of the linked dummy sector, these will scroll the fake mid-texture doors.

Changing to the 1 unit scale, we add the linedefs that the fake doors will use. 2 sets face outwards and will have the door mid-textures we want. 2 sets face inward and use a special door-edge texture to create the illusion of thickness. The right-hand set will be tagged with the upper scrolling linedef's tag in the linked dummy sector, and the left-hand set will be tagged with the lower one:

Now we add the mid-textures. We'll first move the real door into it's open position so we can see what's going on, and align the inside mid-textures first.

The door mid-textures are constructed so that they have a blank space equal (or greater) in width to the height of the door, so when they slide out of the way they leave a empty gap.

Now we repeat the process for the outward facing linedefs using the door mid-texture, and make sure we lower the 'real' door back into it's closed position.

With luck the doors work:

However when I build these doors 3 things tend to go wrong.

(1) I forget to close the 'real' door after aligning the mid-texture doors, resulting in a 'closed' mid-texture door that can be walked through and acts oddly. (Fix: Close the 'real' door.)
(2) I link the wrong wall scrollers to the mid-texture and they slide in the opposite direction. (Fix: swap the linedef tags of the dummy sector.)
(3) The 'real' door and it's linked dummy sector inadvertently become unlinked, resulting in bizarre behaviour. (Fix: Join them together again.)



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Thank you for posting this, I haven't looked at the maps in the editor but I was so dumbfounded when I saw this happening. Pretty remarkable stuff!!

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I was planning to do an interlocked base style door which is also possible using this technique 

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Very well done. I completely forgot that Transfer_Heights could be used to make invisible sectors. In the past when I did transparent-texture doors (both vanilla style and with boom scrollers) I would have to muck around with broken sectors, which is a pain when you actually wanted to find any real broken sectors.


Oh god, I can't believe I even had to worry about broken sectors at all...

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