Monster projectile activating W1 linedef...?

Up until Doom 1.2 or so, all projectiles could trigger Wx lines.

After 1.2 this was changed in the source code by adding a list of exemptions to the relevant code, that made certain mobj types unable to trigger them, namely Doom1's projectiles.

EDIT: No longer sure about the below as I've just tested in Doom2.exe 1.9 and found the Mancubus projectiles don't trigger the line.

Unfortunetly, this list was never updated for Doom2's projectiles so even in 1.9, they can trigger Wx lines.

Most source ports add Doom2's projectiles to this list.

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Cool. Whoever invented that made me waste a truckload of my already limited time on earth. Urgh.

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I used similar thing in map18 of hell revealed TAS, with revball triggering W1 teleport near the exit. Stumbled upon it randomly, then RjY explained what happened in this post.

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So what are the rules? Can W1-open-door-once be triggered by _some_ projectiles? Does ZDoom follow the same rules? Can such trickery be used for rare secrets in Doom?

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From what I gathered in the older thread, it doesn't trigger them, but it cancels them.

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id was stupid when 'fixing' this. Instead of using a whitelist of actors allowed to trigger these lines they just added a blacklist - that was incomplete. All Doom-2-added projectiles are not on the blacklist.

In ZDoom most of this has been fixed by implementing sane semantics for what allows to trigger a walkover action. This means, a projectile is classified as such not by being of a specific type on the blacklist but by actually checking for the MF_MISSILE flag - just what id should have been doing all along when checking this.

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interesting, on cl9 the manc shots close the door, but nothing happens on cl2

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In Vanilla Doom, Doom 2 projectiles use up, but don't activate single use trigger types.

Doomsday deliberetely restored this behaviour in Doom, in 1.9.

But in Boom, Doom 2 projectiles use up and activate single use triggers?

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Vermil said:

EDIT: No longer sure about the below as I've just tested in Doom2 and found the Mancubus projectiles don't trigger the line.


IIRC, the Mancubus fireball was present in the first Doom.

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Eris Falling said:

IIRC, the Mancubus fireball was present in the first Doom.



It was added in 1.666. We are talking about 1.2 code here.

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Vermil said:

In Vanilla Doom, Doom 2 projectiles use up, but don't activate single use trigger types.

All of them? Doesn't that mean that one-time permanent effects (such as floors lowering to reveal new areas) can break the game if hit by anything such as highly spread Mancubus or Arachnotron shots?

It has never happened to be stuck because of this, though, so I doubt it applies for all of them.

EDIT: sorry, I read the thread now and it only happens on the monster activateable, which are teleporters, repeatable lifts (no harm) and (!!!) W1 - door open wait close. You can practically make an encounter random or a secret ultra-rare by exploiting this (did Doom 2 projectiles pass here? YOU FAIL, no SOULSPHERE FOR YOU)

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