Speedshots

Speedshots, What are they and how do they work?

So we all know what a speedshot is, it's merely when a rocket hits the ground exactly when the player that fired the rocket also hits the ground.
Great that's solved but what's so special about them?

The SPEED!
The fun, useful part of speedshots is the massive, compounding horizontal velocity and distance you gain.

An important thing to note is that when a player normally rocket jumps and then just stops when they hit the ground they don't stop instantly.
There is 1 tick in which the player's vertical velocity gets set to 0 while the horizontal velocities don't.

Data:

Just landing:
xloc		yloc		zloc		xvel		yvel		zvel
886.652099	295.968750	144.799224	636.895507	0.000000	-653.608825
896.205505	295.968750	134.905090	636.895507	0.000000	-665.608825
905.758911	295.968750	128.031250	636.895507	0.000000	0.000000
909.358886	295.968750	128.031250	240.000000	0.000000	0.000000
912.742858	295.968750	128.031250	225.600006	0.000000	0.000000

Speedshot:
xloc		yloc		zloc		xvel		yvel		zvel
895.636901	172.343704	144.545059	750.914855	56.947010	-559.742309
906.903076	173.176376	136.058929	751.078674	55.511615	-571.742309
918.169250	174.009048	128.031250	836.966918	184.652313	624.239807
930.784973	176.242309	137.304840	841.048400	148.884429	612.239807
943.461914	177.939056	146.398437	845.129882	113.116546	600.239807

So as you can see, looking at the just landing data you see that on the third tick the zvel (vertical) becomes 0 while on the fourth tick weirdly the horizontal velocity gets set to the class' max velocity. (and the reason yvel is 0 is because I was rubbing against the wall when recording the jump)

And when you look at the speedshot data all velocities increase on the thrid tick when the speedshot happens. The zloc during the speedshot is 128.031250 and we can through out the .031250 so 128 is the height of the speedshot platform.
So that's great we know that speedshots happen right when you hit the ground. Except that sometimes they don't.

While testing I got other speedshot recordings that looked like this one:
xloc		yloc		zloc		xvel		yvel		zvel
900.410766	218.700271	146.973480	772.022705	-127.079971	-563.458435
911.991088	216.794067	138.431610	772.022705	-127.079971	-575.458435
923.571411	214.887863	129.709732	984.727050	-51.392929	584.091979
938.294677	213.579071	138.381103	981.551879	-87.252624	572.091979
952.988281	211.911743	146.872482	979.574157	-111.154708	560.091979

Now we know that 128 is the height of the speedshot platform and yet when I got the speedshot I was at 129.709732, a whole 1.709732 units above the ground. What does that mean?

Well, weirdly, it means that I actually got a 'lucky' bounce. Now this is mostly about speedshots but when this happens we don't speedshot on the ground but we do speedshot on the "ground" (the quotes are important).

In TF2 (and all source games), the "ground" is defined as 0-2 units above the actual ground. And for the forward thinking this is how bounces work too.


So I've covered what they are the basics of how they work, but why do they work?
I'll cover the bounce and "ground" stuff later in another one of these posts.

But for now, I bring up one very crucial source for all this nonsense.

THE SOURCE CODE!!!
https://github.com/ValveSoftware/source-sdk-2013

Specifically this one function in this one file:
https://github.com/ValveSoftware/source-sdk-2013/blob/55ed12f8d1eb6887d348be03aee5573d44177ffb/sp/src/game/server/physics_main.cpp#L1840

What that one function basically does is control the friction generated from the platform you land on, and adjust speed accordingly.
That is the whole backbone of not only speedshots but also bunnyhopping and edgebugs.


Now again the astute of you may think that some textures have lower friction than others, so would that make speedshots any easier on say glass or ice?
Well you'd be correct about the friction thing, but sadly no speedshots are no easier on low friction textures. The horizontal velocities get set to the class's max velocity too fast.

Data:
xloc		yloc		zloc		xvel		yvel		zvel
955.318298	-38.236213	-348.044342	510.637817	148.685989	-615.414489
962.977844	-36.005924	-357.365570	510.637817	148.685989	-627.414489
970.637390	-33.775634	-366.866790	510.637817	148.685989	0.000000
974.093872	-32.769195	-367.968750	230.430297	67.096008	0.000000
977.420715	-31.800497	-367.968750	221.789154	64.579902	0.000000



But that's not really that important. And yes if you could make a texture with 0 friction in theory you could speedshot at any time
BUT frictions are based on the "$surfaceprop" value in the VMT and there are only so many that Valve has made available, and I don't know of any that have friction of 0.

From https://github.com/ValveSoftware/source-sdk-2013/blob/55ed12f8d1eb6887d348be03aee5573d44177ffb/sp/game/mod_episodic/scripts/surfaceproperties_ep2.txt

"friction: this is the physical friction (0 - 1.0, 0.01 is slick, 1.0 is totally rough)"



All data sourced from jump_rebound_v3 and jump_hexahedron using Jrecord, or the github repo linked above.