Thank you very much Preach for this long and informative answer. I was under a wrong assumption all the time - but your info closed all the gaps and cleared things up for me!
And thanks again Metslime! 

I know you want to avoid using a mod but just in case: in progs_dump 2.0.0 you can use any model for a key and customize it's name and a bunch of other goodies. 

Thank you @dumptruck_ds I have had a look already. It offers a lot of great things I have been dreaming about. 

Let's say I'm making a little "episode" of several levels. Would I be able to rig up a "Congratulations" screen of text like the normal ending of Quake?

I tried searching through end.map and wasn't sure where to look. Tried searching this forum, but I failed to produce search terms that narrowed it down. 

The end txt 9is captured in the boss_gate function. When captured four runes and defeat the old one with the messier object entering the transporter thing simultaneously, you'll get to the end screen. From there it is altering the progs.dat txt file with your message.

You need a setup with each episode a rune. Then make an end map in which you encapsulate the defeat of the oldone, or one of your own end bosses.

It can be easier to use the freeware version and use the killing if Cthong as your end level. That way you can look at the original files to compare with yours. 

the text for the intermission screen is in quakec, not in the map itself. So to change it you would need to make a mod. 

How engine-agnostic are transparent textures (or is the correct term "fence textures"?) I remember seeing them for the first time in the Rubicon Rumble Pack, but now, as I'm slowly getting back to Quake after a bit of a hiatus, it seems maps that *don't* have them are almost in the minority. I'm talking about things like vines, foliage and grating, as well as various little 2d details that almost look like sprites (I assume those all rely the same basic technique).

Has this become such a standard feature that most/all modern engines support it, kind of like skyboxes? And what happens otherwise? Are the transparent parts displayed as a solid colour, or would the map just not run at all? 

Out of recent Quake sourceports, I've only used Fitzquake Mark V and Quakespasm (and QuakeSpasmSpiked). They both support these just fine. Despite Mark V having some useful features and the 'proper' underwater warping, I would recommend QuakeSpasmSpiked.

If the engine for some reason does not support these type of textures, then it should look something like this:

http://gila.deathmask.net/various/mvwq_fence.png

It's a screenshot from Alkaline start map using Mark V WinQuake version. As you can see the fence textured brushes aren't transparent and instead rendered with solid colors. Also, these blue sloped windows on the right should be translucent. 

Thanks very much for the screenshot and the info regarding QS and Mark V.

Which engine are you running in that screenshot, though? It'd be good to know which one do *not* support transparent textures.

As for the recommendation to use QSS, I was actually asking more from a mapper's than a player's perspective. I'm aware that QSS will run just about anything you throw at it; I'm more concerned about creating something that will only be playable in a limited number of engines. For that reason I'd rather not use QSS as my (sole) testing engine. ;) 

It's a screenshot from Alkaline start map using Mark V WinQuake version.

Don't know how I read over that. D'oh! 

That screenshot is from MarkV WINQUAKE variant which renders like old software-mode WinQuake (or original DOS Quake) did - in 256 colors and no support for advanced things that came later. I made it just to demonstrate how these things might look.

The regular variant of Mark V uses DirectX 9 and renders these transparent textures just fine. It has some useful built-in tools for mappers, as shown in this video from 2:50 - https://www.youtube.com/watch?v=dMOF3l2MtlI

I also quickly tried DarkPlaces, it supports transparency, and DirectQ - it does also, but not in all the cases, I don't know the details.

And these days I'm not sure there are any other frequently used sourceports, for single player at least. Well, there's vkQuake but it does everything QuakeSpasm does, because it was based on it. 

Thank you for that very elaborate response, gila. I really appreciate it.

Only after I posted my initial response did I notice that you had already specified which engine you used in the screenshot. Sorry about that! 

Hi, I am new to mapping and id like to make doors, that open after activating 4 buttons. How to do it? I know ho to do it with one button, but not with four. 

All 4 buttons should target a trigger_counter with a “count” of 4, then the trigger_counter targets the door 

i am using trenchbroom version 2020.2. trenchbroom is telling me that i have a hidden group and i am having a very hard time trying to find whatever group trenchbroom is saying is hidden. the only layer i have is the default layer. i have ungrouped just about every grouping that i had. i am thinking it is time to just call this quits and start anew with another map.

another issue is that i want to basically open two copies of trenchbroom or 2 maps at the same time where i can transfer objects from one map to another map. i have drump truck ds's videos. he stated in one of them that a person could pre create objects and then transfer them to a map they are working on by operating 2 trenchbrooms at the same time. i have not been able to do this as trenchbroom regulates to the map currently being worked on. i did place trenchbroom in 2 different directories and it did allow me to open two at a time but one of them crashed.

EARP 

I think the very first thing you should try is use the newer 2021.1 release instead. I don't know for sure if it will fix your issues, but it should be a better starting point for getting things figured out. 

@Joel B

i updated the version of trenchbroom and i believe i may have found the hidden group but i am still unable to transfer objects between maps as was stated in one of dump truck ds videos. i just started over from scratch (took down the specs of the objects i had created). one can spend a lot of hours wasting time looking for a way out of a problem when they can just start over like me. :) 

does anyone know how to create the glass look in quake or making a ladder that allows the player to climb it ?

i have not found an answer to the glass and i have witnessed a ladder, i do not remember the map names but i am looking for the one that has the glass in it (it was see through and i am not sure if it was breakable or not. 

For glass, just set the entity “alpha” to a value less than 1. (Requires engine support but almost all popular engines support it)

Ladders: requires a mod, the exact implementation depends on a mod. Some mods include rubicon 2, rubicon rumble pack, alkaline, arcane dimensions, quoth, and I think progs_dump.

Without a mod, you can make ladders as an extremely steep staircase where each rung/step is 16 units tall and one unit deep.