The Juicy Stuff: Advanced Physics Exploitation
Okay, here is where we get into the really,
really juicy stuff - the things that make onlookers' jaws drop, and gives you the edge in a 1-on-1. Before I launch
into these moves I'll mention firstly that with a dial-up ping most of them become exponentially difficult, and
some adaptation will be needed in order to use them over the internet.
Strafejumping
Strafejumping gives a significant boost to a single jump, and is performed by holding down either strafe key while
jumping forward. During the jump, it is important that the forward key and the strafe key are held down for the
entire jump. You will need to turn a little in the opposite direction you are strafing in order to jump in a straight
line. Strafejumping is most often used to reach places where normally one would have been required to take an alternate
route. For example, in q2dm1 a strafejump can be used to jump to the two 25-health boxes in the Central area from
the walkway running out of the megahealth room (see Fig. 7).
Things like this may seem irrelevant - you only save about a second doing this particular example - however as any top-rung Quake II player will tell you, in a pursuit one second can be the difference between life or death.
Another useful place strafejumping helps is the previously mentioned jump to the megahealth in q2dm1 by first doublejumping onto the backpack blocks, then to the light, then to the megahealth. With practice, a strafejump can be used to jump from the top of the backpack blocks directly to the megahealth, erasing the need for the light. For the skilled strafejumper, the next step is to jump back from the megahealth onto the top of the backpack blocks - useless, you may think; until you then strafejump to the yellow armour (a difficult, but possible, jump that requires very precise positioning and timing). See Fig. 8 for a visual explanation of this maneuver.
Bunnyhopping
An unusual phenomenon occurs if one performs a series of strafejumps one after another with no break in between
- the player will actually gain horizontal velocity with each jump, and while there is a hard limit as to how much
velocity can be gained the resulting speed is quite dramatic. The important thing about this trick is that you
must make sure you do a full strafejump each time, which means if you're going on a straight line you may need
to alternate left and right strafe, or just keep turning with the mouse if you're going around a bend. The other
vital part to this is the fact that there must be no delay between each jump - this can be ensured by releasing
the jump button after each jump, then pressing it and holding it before you hit the ground. This will make you
jump automatically the instant you hit the ground.
Bunnyhopping has a limitless array of uses - once one becomes proficient at bunnyhopping you should be using it all the time as a general way to go faster (unless, of course, you need to remain silent for ambush purposes). Also, there are a few places on the dm levels where bunnyhopping can allow one to reach places normally requiring a rocketjump, for example. The best example is - once again - q2dm1, and the upper rocket launcher. If one bunnyhops along the passage leading to it, and times it so the last strafejump is performed on the edge of the platform; correct placement will make one sail right over to the opposite side of the room, landing them on the ledge containing the health, rockets and armour shards. If this trick can be performed a good percentage of the time it becomes an excellent way of gaining 10 rockets.
One characteristic of bunnyhopping is the fact that if a large drop is made somewhere throughout the series of jumps, providing the player keeps strafing and moving forward and jumps immediately upon impact with the ground; they will continue along at the same velocity. This can lead to an odd cannon effect, as if the player is eventually falling almost straight down it can appear very much like they have been shot out of nowhere as their horizontal velocity is not affected by the fall. This in itself has uses - one, which is quite difficult to do but can be useful; is on the walkway in q2dm1 just under the upper rocket launcher (yes, you are right in saying that this area contains an abundance of trick spots :). One can perform a strafejump off the ledge at an angle of about 45 degrees, and land on the staircase below and immediately execute another strafejump - hence bunnyhopping. If timed right, with a bit of luck you'll be shot out onto the ledge over the other side of the room. Refer to Fig. 9 for positioning.
Circlejumping
Circlejumping is a relatively new style of jump, having only recently been discovered by the trick-jumping community.
Its exact reasoning is unknown, however it can exceed a strafejump in terms of distance jumped. However, it is
considerably more difficult to pull off than the strafejump. It involves running perpendicular to a ledge, then
arcing around by slowly turning the mouse to the direction of the intended jump, and jumping when you're facing
a little before the target. Then, turning is sped up a bit and the forward key always held down. The most important
aspect is that you must be turning throughout the entire jump.
Fig. 10 shows how circlejumping
can enable one to reach the same ledge as mentioned above in q2dm1 with a single jump from the walkway (thanks
to RD|Julios for the demo).
Circlejumping in reality is not all that useful unless you can execute it consistently.
It is, as I said, a very difficult jump so don't be too bothered if you can't pull it off at all.
Cratejumping
Cratejumping is a bug in Quake II that has been known for a while, but has only very recently (the day this article
was written, as a matter of fact) been explained. Anthony Bailey - of Quake done Quick fame - has been hard at
work with Nolan Pflug, other members of the QdQ team and myself (and I'm sure others I've forgotten) to try and
explain the phenomenon.
What cratejumping does is allow one to jump onto crates that usually can't be reached. In his conclusions, Anthony presented a very detailed and complex report that I will summarize here.
There are three aspects of Quake II's physics that all combine together to allow the phenomenon that is cratejumping. The first - known as bouncing, or bounceback - involves an odd feature that allows one to gain more height by jumping twice. What happens in Quake II will add approximately one hundredth of one's downward velocity to their next jump, provided the next jump occurs immediately after the landing of the first fall. This means that if you are falling at a velocity of 270, you will jump 2.7 velocity units faster for the next jump. With a normal jump followed by another jump this yields about one extra unit of height. Next, 'frame quantization' occurs when a player jumps and in order for them to make it a certain height the peak of their jump must occur within a very short amount of time. If a player's computer is achieving only a low framerate there is the chance that the player may miss the peak of their jump, hence not making the required height. For most purposes, a framerate above 30 fps will prevent frame quantization from having a noticeable effect.
The final 'feature' - that which has the most effect - is rounding. Quake II, for each frame, will round off the player's current location to one eighth of a unit - but it will round it towards zero every time. For example, if the player's z-coordinate is 34.92 it will be rounded down to 34.875. Because this is done for each individual frame, it can have an effect on jumping height - especially if the computer is yielding a high framerate. However, what happens if the player's position is below the z-axis? Their z-coordinate will be a negative, and hence the rounding will round up. This means that if you are in what's known as negative z-space - that is, below the z-axis - you will jump higher than if you were in positive z-space.
Also, if you have a high framerate you will hence jump even higher in negative z-space, but even lower in positive z-space. Confused yet? =). With a framerate of 70 fps, one should expect to jump roughly 3 units higher in negative z-space.
Now here comes the point of all this - if you combine the 3 units from a negative
z-space, with one unit from a bounce, and have a high framerate to ensure frame quantization doesn't come into
effect... you can bounce onto a block of 64 units high, which normally could never be done. Unfortunately, there
exist only a very small number of places where one is actually ever in negative z-space. One spot, however, is
most of q2dm8.
Currently, only one area in the q2dm# deathmatch level series has been found to contain crates existing in negative
z-space - that is the majority of the crates in q2dm8. The QdQ team is hard at work trying to find similar crates
in the single-player levels to aid their run time, and it appears that some others do exist.
About the only real practical use of cratejumping is if you have a killer system you can grab the rocket launcher in q2dm8 quickly by two or three cratejumps. See Fig. 11 for a visual guide to one of the methods that can be used for this shortcut.