Is it possible to scroll ceiling textures a set amount?

[Guest]

Basically the title, all I've found is ways to scroll the floor or ceiling textures indefinitely. I just need to scroll them for a certain amount, like 128 units.

The reason for this is that I saw a map that had a sliding hatch over a elevator that raised from under the floor. The "hatch" was just a large texture with half of it transparent (over a non-solid 3d floor I think) that he made scroll to look like it was opening. So, that's the effect I'm trying to replicate.

BUT, I only had a video of it, and the author's description of how he did it at the time, and I forgot where I originally got it from, so I'm trying to find it again, or at least figure out exactly how it was done.

[Guest]

You can do it with the action special 224: Scroll Ceiling and by using a dummy sector to control the scroll. The ZDoom wiki isn't very clear of this:

https://zdoom.org/w/index.php?title=Scroll_Ceiling
https://zdoom.org/w/index.php?title=Scroll_Floor

Draw a dummy sector outside the map area so that one of it's linedefs is parallel to the direction where the ceiling texture should scroll. For this line give it the special and arguments:

Action: 224 Scroll Ceiling.
Sector Tag: to the targeted ceiling.
Options: 1 Displacement *and* 4 Scroll by dx/dy.
Scroll: texture only
Horizontal: don't scroll
Vertical: don't scroll

Now the targeted ceiling will scroll when the dummy sector floor or ceiling moves up or down. It'll scroll in one direction when the floor goes down, the opposite when the floor goes up. The speed of the raise/lower will control the speed of the scrolling. The scrolling distance in map units is calculated from:

(1/32) x (the length of the 224 action line) x (the lower/raise movement of the dummy sector ceil/floor)

To scroll 128 units set the action line length to 32 and lower the dummy sector floor by 128.

[Razumen]

Thanks! Works like a charm, and much better than the hacky way I was going to try it with delays.