How does partial invisibility work?

[DoomGappy]

I'm working on a map that would have a stealth route, somehow, and I wanted to use the partial invisibility powerup to achieve that, but apparently enemies still wake up when you walk in front of them. How does this little thing work? And why is it not just simply invisibility instead of partial invisibility? 

[RjY]

If you are partially invisible, a random angular deviation is made to the monsters' aim. [1], [2]

That's it. That is its only effect.

[JadingTsunami]

In traditional Doom and most of its derivative ports, the Partial Invisibility sphere adds random spread to enemy attacks. The Doom Wiki has a good breakdown of the behavior.

 

In ZDoom ports, idle enemies also won't alert when the player is in their line-of-sight. They still react to sound, though.

 

"Stealth" sections are possible but rely on the player not bumping into monsters and not making any sounds. The Partial Invisibility powerup doesn't help there. If you want a stealth section with a time-limiting component, you might consider using the Light Amplification Visor instead. In that case, you would make it so the player can only see how to avoid the monsters if they have the visor.

[Matt Eldrydge]

It's less "invisibility" and more "all monsters now have a 33% chance to shoot directly in your direction", which makes chaingunners a laughing stock (play Machete map 03 for a quick example) and arachnotrons one of the most despair-inducing monster to face out in the open. Here's a vid by Ducino which goes into more detail.

 

 

If you want a stealth route, I think you could achieve better result by using monsters set to ambush, sound-blocking linedefs and walk-over triggers as well as self-referencing sectors for walls monsters can't see through.

 

P.S.: I don't know if it's actually a 33% chance or not, but it kinda feels that way. What matters is they'll usually not shoot straight ahead if you have a blursphere active.

[DoomGappy]

12 minutes ago, JadingTsunami said:

In traditional Doom and most of its derivative ports, the Partial Invisibility sphere adds random spread to enemy attacks. The Doom Wiki has a good breakdown of the behavior.

 

In ZDoom ports, idle enemies also won't alert when the player is in their line-of-sight. They still react to sound, though.

 

"Stealth" sections are possible but rely on the player not bumping into monsters and not making any sounds. The Partial Invisibility powerup doesn't help there. If you want a stealth section with a time-limiting component, you might consider using the Light Amplification Visor instead. In that case, you would make it so the player can only see how to avoid the monsters if they have the visor.

I hadn't thought about that, but that's a pretty amazing idea. I kinda want to make a map that is completely beatable in pacifist mode, even though I'm not a big pacifist myself when it comes to Doom. At the same time, the player can take a guns blazing approach and beat the map without caring much about being undetected. This has given me some ideas on how to proceed. 

Now I'm more curious as to why the guys at ID did not make the player completely invisible with this powerup. Missed oportunity, I guess. 

Edited February 16 by DoomGappy

[Maximum Matt]

It's predator mode.  More valuable in multiplayer

[maxmanium]

1 hour ago, JadingTsunami said:

In ZDoom ports, idle enemies also won't alert when the player is in their line-of-sight. They still react to sound, though.

 

I swear that they sometimes still wake up randomly sometimes when walking in front of them despite this feature. Is there anything else to it?

[DoomGappy]

23 minutes ago, maxmanium said:

 

I swear that they sometimes still wake up randomly sometimes when walking in front of them despite this feature. Is there anything else to it?

It happened to me as I was testing it too. That's exactly why I created the thread, in fact. I thought they reacted to the sound of me picking up a key, but it seems more like it's a random thing, like the leaky radiation suit.

Edited February 16 by DoomGappy

[Shepardus]

1 hour ago, maxmanium said:

 

I swear that they sometimes still wake up randomly sometimes when walking in front of them despite this feature. Is there anything else to it?

I think it's more like Heretic's shadowsphere, which reduces the likelihood of enemies noticing you but doesn't eliminate it entirely. Haven't looked at the code, though.

 

Edit: Okay I got curious and checked, the default ZDoom partial invisibility behavior is in fact the same as Heretic's shadowsphere (not including the part where some attacks go through you), but I actually had no idea how the shadowsphere worked. You escape detection by a monster if you're a certain distance away from it (128 units) and are not traveling over a certain speed (5 units/tic). Even if you don't fulfill these conditions there's still a 7/8 chance (per A_Look call) you don't get detected anyway.

 

I never liked how ZDoom makes this the default behavior. For all that people bicker about texture filtering, I think this is worse, as it straight up changes a powerup's function and people don't even realize it until they ask on Doomworld. Even the "Doom" compatibility preset leaves it like this (at least the "Doom (strict)" preset does set the appropriate flag).

Edited February 16 by Shepardus

[DNSKILL5]

It works as a camouflage in deathmatch 

[ReaperAA]

4 hours ago, DoomGappy said:

I'm working on a map that would have a stealth route, somehow, and I wanted to use the partial invisibility powerup to achieve that, but apparently enemies still wake up when you walk in front of them. How does this little thing work? And why is it not just simply invisibility instead of partial invisibility? 

 

If you are looking for some examples of Stealth in Doom maps, I recommend looking at some maps like Map32 of 1000 Lines 2, Map26 (The "Silence" challenge segment) of Eviternity II or some maps of Doom Zero (don't remember the map numbers, but the wad definitely had some stealth maps).

[DoomGappy]

10 hours ago, Shepardus said:

I think it's more like Heretic's shadowsphere, which reduces the likelihood of enemies noticing you but doesn't eliminate it entirely. Haven't looked at the code, though.

 

Edit: Okay I got curious and checked, the default ZDoom partial invisibility behavior is in fact the same as Heretic's shadowsphere (not including the part where some attacks go through you), but I actually had no idea how the shadowsphere worked. You escape detection by a monster if you're a certain distance away from it (128 units) and are not traveling over a certain speed (5 units/tic). Even if you don't fulfill these conditions there's still a 7/8 chance (per A_Look call) you don't get detected anyway.

 

I never liked how ZDoom makes this the default behavior. For all that people bicker about texture filtering, I think this is worse, as it straight up changes a powerup's function and people don't even realize it until they ask on Doomworld. Even the "Doom" compatibility preset leaves it like this (at least the "Doom (strict)" preset does set the appropriate flag).

That's interesting. Just for curiosity's sake, is the powerup behaviour something that could be changed through dehacked? I feel like having a total invisibility sphere would be a cool powerup to have for sections like these. 

[Matt Eldrydge]

My experience with dehacked is pretty limited, but I don't think you can make this change through it. Dehacked is more like copy/pasting, if something isn't present in the game data then you can't replace or mess with it. You can edit everything in the WAD, but you can't add new functions beyond what is already there if that makes sense.

 

Then again, Doom mappers repeatedly show impossible things aren't actually impossible, just rather tricky to achieve.

[Tompig]

How does it work? 

 

That's the secret champ, it doesn't.