Plasma bumping [grabs and how to perform them]

Is there a trick to it? I can do it maybe 25% of the time. It's very important on maps like SSl2.

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The term is generally used by deathmatchers for what the rest of us call grabs. That's because in DM (and coop), it occurs in Doom2 map01 (most popular DM map) as a quick way to get the plasma gun. It has nothing to do with plasma really.

What exe are you using? Some make grabs much harder than others. But assuming you are using vanilla or a port that doesn't change this aspect of game mechanics, the main thing is just to slam yourself into the wall with as much speed as possible (straferunning helps, as can wallrunning, a thing glide or a rocket boost), and as close as possible to the item that you want to grab.

Some grabs work a little differently though. For instance, on e4m1, the red key can be grabbed through the bars by kind of rubbing up against them. And the BFG grab in e4m2 seems to need to be done straight on (not straferunning). Some grabs appear to be just on the limit of what is possible distance-wise, and require very accurate positioning and work in a way somewhat akin to a glide, where the grab occurs only when you are exactly in the right place from a "micro-unit" viewpoint.

I'm not sure if anyone has researched this in much detail. Another interesting case is the one I found on ks map19.

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Ah, yes, that clipping error that lets you pick up keys that the authors thought they could dangle just out of your reach. THIS'LL SHOW YOU!

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Angle of player, SR-40, SR-50, Direction(north/south/east/west), and sometimes a tiny turn after bumping can grab it.

For SSL2, I use lift to pillar (D2M1) and usually SR-50 speed bump with twitch.

Its all practice and watching demos. D2M1 demos have some similar bumps as SSL2.

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On the note of grabs, does anybody know how to get the blue key-card on map 09 of Equinox? I've only found it possible to reach it using a grab.

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Doomhuntress said:

On the note of grabs, does anybody know how to get the blue key-card on map 09 of Equinox? I've only found it possible to reach it using a grab.


That's the idea. The area behind the blue door is a secret anyway so it's reasonable that it should require a special trick to reach it.

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I see. I ran into the blue key once by accident, so I assumed that was how you got it.

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i made an example demo for the map01 plasma bump. it's a solo player deathmatch, so you might need advanced console commands for anything else than the latest prboom+. i'm not a finn or chewy, so my bumps aren't 100% perfect, but i guess even that has its value, highlighting what's harder or whatever. the ssl2 bump should become trivial after watching/practicing this. :p
http://www.doomworld.com/vb/showthread.php?s=&postid=953692#post953692

short explanation:
- the western one (from the elevator) is trivial, just run straight at the pillar. don't strafe, use the full distance.
- the northern one (from the hallway) is still fairly easy, it's your typical sr-whatever bump. doing it backwards risks missing the pillar. :)
- the eastern one is rather tricky, because you need strafing and some distance. humping it at the NE corner helps.
- the southern one is the master bump, you can only perform it from the spawn position. different players will explain it in different ways. i start running forward, then turn a bit and strafe left with sr40, but it's still voodoo for me.

edit: typo

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Good explanation there.

I also find the spawn-bump to be quite difficult. Currently, if I'm paying attention when spawning (which is actually pretty hard in itself), I can bump it maybe 1 out of every 5 or 6 times. If someone knows a good method on this one, I'd love to hear it. The only one I can get 100% of the time is the lift bump.

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blarg, i quoted instead of editing. i don't get the southern grab reliably either, but it definitely gets above 50% after i practice and focus. dopefish (a cz player) once told me it gets easier when you use turn right key instead of mouse turn, but my personal setup makes this unpractical, so i wouldn't know.

i should also mention here that this grab (and the others) gets easier on north american servers running the pseudo-oldschool zddl dmflags dubbed as "kist-physics" sometimes. :) skulltag grabs also seem easier, because afaik they were done through a hotfix after much of alexmax bitching, but not really tested by map01 freaks like with oce for zdaemon.

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Wow, so there's more to plasma bumping than I ever knew.

The bump from the south side is interesting. It's almost as if you're more likely to get the rifle if you're moving slower - which actually makes some sense if you consider the quirks of northward movement. As I understand it, if the player is moving north (or east) at a rate faster than 30 units/tic, then his movement in each tic is split in half and each half is calculated separately. So, I don't know how collision detection with items works, but it may be that you're more likely to perform that bump successfully when moving at, say, 20 units/tic than when moving at 32/tic, because in the latter case the game will consider a distance of 16 units twice, which essentially wouldn't reach as far.

I don't know, I'm just guessing.

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That would also account for how the BFG grab on E4M2 works, in which the player is running east, and the red-key grab in ks19, where he is running north. In both cases straferunning appears to fail.

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