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deeplinks

1% damage bug

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I think I found a bug. When player in Doom receive exactly 1% damage, the screen will not flash red at all, and face on status bar will not change. I checked, and bug is present in vanilla Doom 1.9, ZDoom 2.7.1 and PrBoom+ 2.5.1.3. Is this bug known?

It can easily be demonstrated: start E1M1 on "I'm Too Young To Die" and go to courtyard, then pick blue armor and stand in the nuclear waste pool (it will deal 1% damage to player).

The bug happens because damage is added to varirable "damagecount" (it becomes 1), but then it decreases by 1 and set to 0 the same frame before drawing screen (if (player->damagecount) player->damagecount--;), so both screen palette and status bar face will not react (damagecount is 0 already when screen is drawn).

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I noticed this one years ago, I think it's been documented. I assume it hasn't been changed in source ports because it's such a negligible oddity, even more so than the 'ouch face'.

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Is this documented on the wiki? I couldn't find anything.

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Doomguy is so tough that 1% damage doesn't even register in his senses. That's how boss he is.

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Maes said:

Doomguy is so tough that 1% damage doesn't even register in his senses. That's how boss he is.

Is he? Or did the UAC splice some of his genes with that a frog during his supersoldier development phase?

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Maes said:

Doomguy is so tough that 1% damage doesn't even register in his senses. That's how boss he is.

He does grunt in pain, though.

bradharding said:

Very nice find! Just implemented a quick fix in DOOM RETRO here.

I think better fix would be this:

player->damagecount += damage;	// add damage after armor / invuln

// Next two lines added
if ((damage > 0) && (player->damagecount < 2))
player->damagecount = 2;
because you can receive 1% damage multiple times during one frame.

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deeplinks said:

I think better fix would be this:
....
because you can receive 1% damage multiple times during one frame.


Yes, that seems better to me too!

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deeplinks said:

He does grunt in pain, though.

Only because of id trying to economise on resources. The player pain grunt, in this case, is being used as a "hmmph, is that all you got?" sound. ;)

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Has anyone ever taken damage yet didn't at the same time? That happened to me in one of my demos. In my Hell Revealed Skill 1 run, I shot a rocket at a group of monsters. It was close enough that I heard the pain sound, yet my health didn't go down.

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Do you remember where approximately that happened? Sorry, I don't feel like watching a 2 hour and a half demo. :)

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Revved said:

Has anyone ever taken damage yet didn't at the same time? That happened to me in one of my demos. In my Hell Revealed Skill 1 run, I shot a rocket at a group of monsters. It was close enough that I heard the pain sound, yet my health didn't go down.

Yeah, that can happen only on Skill 1: each damage you receive got divided by two, so when you receive exactly 1 damage from rocket splash damage, it got reduced to 0 damage, but game doesn't check that and play pain sound anyway.

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deeplinks said:

Yeah, that can happen only on Skill 1: each damage you receive got divided by two, so when you receive exactly 1 damage from rocket splash damage, it got reduced to 0 damage, but game doesn't check that and play pain sound anyway.


OH NOES THE CURSE OF REGEN HEALTH HAS CREEPED INTO DOOM FROM THE WEAKEST LINK!!!

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deeplinks said:

Yeah, that can happen only on Skill 1: each damage you receive got divided by two, so when you receive exactly 1 damage from rocket splash damage, it got reduced to 0 damage, but game doesn't check that and play pain sound anyway.

I never noticed this one, two great finds in one thread.

Has someone added this stuff to the wiki? I thought it was there but I can't find it now.

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