Stairway to Heaven

How to make a ladder and use CLIP brushes

Ladder in the Stables

First encounter in original map village3 - Stables

At the time I discovered Hexen II, I was immediately struck by its ladders. Being able to go magically straight up or down was such a cool (and realistic) way of exploring and such a nice change after the usual ramps and even more classic stairs and moving platforms known for as long as Doom itself! It may sound strange that I praise it so much because maybe you think it's just silly static architecture with absolutely nothing spectacular. But it's not how I see it and you're on my website, so let me explain how you can make your own ladders to exploit a real 3D architecture and give the player more variety to experience it.

For a long time I believed the brush scaffolding was encompassed inside trigger_push or trigger_whatever (something they actually did in Quoth for Quake maps with their aptly named trigger_ladder). But not at all! It's actually far more simple. It's... well... a trick! I had a hard time figuring out when I first wanted to solve the mystery because no trigger_whatever was visible in the map once it was decompiled with Bsp2mph2. Contrary to how I work usually, I turned TrenchBroom into 2D view in the hope that it would help, and that's how I unveiled the ladder's secret.

Ladder in the Stables unveiled

What a mess! No wonder the obvious didn't immediately jump out at me!

The trick is right in front of your eyes. Can you see it? Okay no more suspense: the ladder is nothing more that a super steep staircase! It looks absolutely vertical but is not: each step is offset by one unit from the one below. If you carefully pay attention, on top of the ladder you'll see the small gap between the step and banister front faces which doesn't exist at the bottom (that clue could actually be removed by making the banister accordingly steep instead of vertical; it would still look vertical to the player).

And now everything is explained: why you can go so easily up or down, or even stop halfway (you rarely experience that because ladders are usually never high enough).

So now let's go a bit further...

A broken ladder in Wheel Of Karma

This ladder appears somewhere in Wheel Of Karma: A Tulku Odyssey. It is not pretending to be vertical at all, which is pretty common with ladders seen in custom maps: here for aesthetic reasons, but more often than not because the false vertical ladder trick above is unknown to many mappers so they cannot do otherwise. What makes things worse is that the visible brushes of such steep ladders are usually the only ones they're made of. In other words, going from one step to the next means jumping to it, and the player has to do some silly hopping climbing.

Time to go for a second trick for the price of one! Here is how this ladder is designed in TrenchBroom:

A broken ladder in Wheel Of Karma

What the player actually climbs is a staircase made out of brushes with the invisible special CLIP texture. The staircase evenly goes up so that the move is fluid and never obstructed by anything (notably not the the rungs broken for decorative purposes). The player is not embarrassed in his comfort of movement by a poorly designed architecture. Actually the banisters are even func_illusionary entities, just to be sure they cannot be a nuisance.
Note that the grid on the screenshot is 4 units, so each step is 12 units high. This is not the maximum. Each step may be up to 18 units. Above that value, the player cannot just walk over seamlessly anymore and has to jump. On the other hand, no matter whether the rise looks vertical or sloping to the player's eyes, the actual steps must be absolutely vertical, otherwise the player will get frustatingly stopped in their move, even with very low steps. If the slope makes an uneasy or varying angle, play with the steps' height or depth instead (like I did, look above) but always keep them strictly vertical.

I use CLIP brushes for a similar purpose to facilitate rock climbing: if what looks to the player like a steep slope or a messy rock pile is actually a staircase, obviously the ascent won't be such a problem! So remember the trick where jumping from a platform to the next is not where you intend to put the challenge (of course the configuration of the area must be such that the presence of your invisible staircase will not be noticed by the player nor give them the feeling of an improbable levitation!).

Let's finish with a third related trick (wow, it's clearance day!).
Still to ease player movement, use CLIP brushes in horizontal settings as well. Remember players are plunged into a hostile world where danger can arise at any time. In such a situation, what would you do in their place? You would probably hug the walls! Please consider that this is exactly what they do all the time while playing and running everywhere, and imagine how awkward, inappropriate and irritating that would be for them to be continually trapped by columns slightly protruding from the walls, salient angles and other similar stuff.

That's why each time the player sees this kind of setting in-game, they should actually be facing that one:

CLIP brushes in-game CLIP brushes in TrenchBroom

In any situation, the player is so gently pushed by invisible brushes in the right direction that they never or hardly notice. And in case you wonder, yes the small angled beams are func_illusionary entities to avoid banging their head! So everything is smooth.

Want to ask for clarification, report an issue with this trick or propose another one? Drop me an email If you use the trick please credit me and put a link to this website.