Things about Doom you just found out

[Gez]

The inverse-grayscale colormap used for invulnerability is bugged!

Okay, that one is very subtle and really unnoticeable. There's a typo in dcolors.c, the utility that Id Software wrote to generate the palettes and colormaps for Doom.

Here is the bug:

	for (c=0;c<256;c++)
	{
		red = *palsrc++ / 256.0;
		green = *palsrc++ / 256.0;
		blue = *palsrc++ / 256.0;

		gray = red*0.299 + green*0.587 + blue*0.144;
		gray = 1.0 - gray;
		lightpalette[GRAYCOLORMAP][c] = BestColor(gray*255,gray*255,gray*255,palette,0,255);
	}

The people around here who know a bit about color and video might recognize the values used to weight the red, green, and blue values to generate the grayscale value: they are the traditional Y luminance values used in stuff like this. But there's a typo. It should be 0.114, not 0.144, for the last weight.
Because of that, the sum of the three weights is greater than 1.0. So the colors are found slightly more luminous than they actually are, and since it's inversed next, they end up slightly darker than they should. Most of the difference is eaten by palettization afterwards anyway; but it can nonetheless be seen if you pay attention.
Here is the colormap, with the inverse gray map vertically stretched to help make it more noticeable. The grays on top are from the IWAD; the grays on the bottom are what the same algorithm would have given without the typo.

(If you don't see it, click to zoom and it might be easier to notice.)

[printz]

All this colorimetry and analog TV stuff makes me lol.

[K3K]

Scypek2 said:

There's a sprite of a gray version of stalagmite without spikes that is not used in the game.

Yeah I was messing around with Doom2.wad in XWE and I saw that too :P

[tempun]

Maes said:

It was interesting to see that for "orbiting" to happen, the player doesn't stricly need to near the center of a circular orbit, but can also be near one of the two foci of an ellipse, at least an ellipse with an ε<1.0 (more squished from the x axis, but with the main axis still being x, not y).

I think the orbits are always circular, never elliptic.

[LigH]

If homing rockets have a limited turning angle and a constant velocity per tick, it is quite logical that they can be lured into a spiral and finally an orbit. But it is funny to watch, nevertheless.

You may remember the "Circle of Death" (strafe right + turn left), it has a similar appearance.

[StoneFrog]

LigH said:

If homing rockets have a limited turning angle and a constant velocity per tick, it is quite logical that they can be lured into a spiral and finally an orbit.

Never seen it attempted in Doom, but it's been done in Rise of the Triad.

[Maes]

tempun said:

I think the orbits are always circular, never elliptic.

From that video, maybe due to incorrect automap aspect ratio, the orbit appeared elliptic with sub-unity eccentricity, and doomguy was closer to the edge of the "ellipse" than to its center. But I guess you could blame that on the ham-fisted precision of Doom's arithmetic, too.

[Koko Ricky]

I've seen revenant rocket orbits several times. A real WTF moment the first time it happened.

[aldiboronti]

Video of a revenant rocket orbiting Doomguy in Doom II.

http://www.youtube.com/watch?v=6ZUkRKf7tpU

[Xane_MM]

StoneFrog said:
Never seen it attempted in Doom, but it's been done in Rise of the Triad.

It's cool how in RotT, the rocet maes a huge circle, yet in Doom II, it is so small! What makes the orbit so big in RotT?

[Gez]

Xane123 said:

It's cool how in RotT, the rocet maes a huge circle, yet in Doom II, it is so small! What makes the orbit so big in RotT?

Apparently, it's just this level. The rocket in question is a heatseeking missile, and there are jets of flames that go off periodically. So the missile regularly switches its target and that syncs well enough to give a perfect orbit. The description to the video says you have to destroy all torches except one, go to a specific point, and shoot in a specific direction to achieve that.

So it is quite different from the revenant's homing rockets.

Other than that, orbit radius is also a function of speed and maneuverability. The higher the speed, and the lower the maneuverability, the wider the orbit.

[Lizardcommando]

I JUST found out how to get that plasmagun in Doom 2's MAP05 thanks to this thread.

[LigH]

One of the most important factors in the efficiency of BFG shots is their slow speed. Right next to the visibility of their impact to both the player and the victim.

If you increase the speed of BFG projectiles, their effect becomes more unreliable. I had situations where I could not kill a Chaingunner by shooting a row of BFG projectiles right next to him or below him (using a "super weapon mod" which makes the BFG9000 shoot like the plasma gun); he died not before a direct hit.

Furthermore, shots may pass thin walls if the player is pressed against them while firing. This may circumvent e.g. simulated safety glass.

[StoneFrog]

Not a "just found out" and not related to Doom per se, but has anybody else somehow never found their way out of Heretic E1M6 by means of the regular exit? I always end up on the secret map somehow...

[DuckReconMajor]

Same here. I searched for hours and found the regular exit once, but soon after forgot where it was :P

[Scypek2]

I had no idea that it is intended to rocket jump anywhere in original Doom, but it seems to be an official way to enter the E2 E3 secret level.

[DuckReconMajor]

You mean E3?

[printz]

Scypek2 said:

I had no idea that it is intended to rocket jump anywhere in original Doom, but it seems to be an official way to enter the E2 secret level.

Heh. I was simply rubbing the outside of the blue wall in search of a secret platform, and I just triggered the exit :P And it was Ultimate Doom, not a buggier version more prone to this.

[Scypek2]

That's actually weird, shouldn't switches be triggerable from the front side only?

[DuckReconMajor]

It gets triggered from the side.

[LigH]

Well, the normal exit in Heretic E1M6 is "too obvious to be recognized" - a big plate to step on, rather unusual as such. But its activation sequence seems to be more complex than the release of the secret exit...

[40oz]

I was playing Reverie today, and I was fighting a Pain Elemental high up in the air. After I killed it, the outburst of lost souls that appear after it is killed were killed instantly by the surrounding walls, one of which managed to get squished and stuck the upper wall by what appears to be nothing at all. There's no doors or crushing ceilings or anything around it. It was just an exploding lost soul, and then it was a puddle of blood. I've never seen this happen before.

[Archy]

40oz, what engine were you using? That's very interesting.

[Scypek2]

I just found out that fast crusher turns barrels into puddles of blood :/

[Maes]

40oz said:

It was just an exploding lost soul, and then it was a puddle of blood. I've never seen this happen before.

Doom's crusher code can be very weird, especially with "crushing floors": while it's not really possible to explicitly define one, the "crushing floor" behavior is coded-in, but it might trigger in unexpected circumstances.

[40oz]

Archy said:

40oz, what engine were you using? That's very interesting.

I was playing in Odamex. inb4 "that's why"

[DuckReconMajor]

I think the fact you're playing with no HUD is more likely than anything.

And do you really use Odamex for single player all the time? How well does this work?

[40oz]

It's got joystick compatibility which is what I'm after, without going overboard with various newschool features.

[Snakes]

Scypek2 said:

I just found out that fast crusher turns barrels into puddles of blood :/

Although there is the floor-crusher that seems to avoid this at an increased rate (I've used this technique only once and it worked properly every time). If anyone could explain to me just why this happens, that'd be pretty awesome.

[TwinBeast]

I just found out that the BFG explosion flashes are very similar to the Teleport flashes.. so is it like a Telefrag gun then? Something that teleports parts (the atoms, etc) of the target into random places inside the target or nearby area and ultimately turns the target into some kind of red jelly.