Hammer Unit

Hammer Unit (HU) is the unit of length (or distance) used in games run in Source Engine, which include Counter-Strike: Source and Counter-Strike: Global Offensive. For any props existing in a map, their dimensions and locations are registered in values and coordinates in terms of Hammer Unit.

Usage

As in real life, units of length are used to tell specific lengths and distances, or extended to area, volume, speed and acceleration. By comparing with known standards recorded in these units, we can briefly get the concept about the real sizes of the thing being described.

In a virtual game environment, people involved in it also have to get a concept on these units in order to feel right in a virtual world. For normal players, they are less likely to study these units and data, but for mappers it is a requirement to create reasonable maps.

HU for mappers

One of the key functions of thinking in HU for mappers is to keep a map in the scale. A Gundam figure could have perfect ratios, but its scale is obviously much smaller than what the "real" one is supposed to be. The purpose of highlighting the "the" is to emphasize that a small variance of scale (< 10%) would still give logical error, in the sights of players. Just as one day your bedroom door is suddenly shortened by 9 inches.

There have been many examples that new mappers ignored this factor and ended up creating a figure-like map that no players can fit in, and due to limitations of the mapping software they have to remake the map from scratch. This shows the importance of recognizing length units also in the virtual world.

Another common use of distance measurement for mappers is to expect how long time the players are required to move from a certain place to a destination. This helps constructing hold points, hold times as well as other Zombie Escape elements very much, or even in defusal maps – time for heading to the bomb sites.

HU for players

Players are not required to know anything about Hammer Units. But for those who have thought about the real dimensions of the virtual maps, distances have to be converted, and the sources are all in HU. This may enhance the gaming experience if you are able to convert them, and imagine you are in the map.

Appearances

Data appeared after inputting cl_showpos 1 in console.

As a player, normally the virtual measurements are not displayed. The interface is shut. Actually it can be enabled by typing cl_showpos 1 in the console, which can be opened by pressing ~ by default. After typing, real-time data will be displayed on the top right hand corner of the game interface. They include

• Position – 3-dimensional coordinate of the player's location, measured in HU, namely
  • x- (West due East),

    

    Angles represented by the first datum.

    

    Angles represented by the second datum.

  • y- (South due North) and
  • z- (feet due head) coordinates.

• Angle – Display the angle of point of view (POV) of the player. It is projecting on the surface of an imaginary sphere, which is in 2-dimensional, thus the third angle is not needed. In the game it is always 0.00.
  • First angle: latitude – display the inclined angle between the POV line and any inverted horizontal plane. "Inverted" means it record angles of elevation as negative, but angles of depression as positive. The extrema are ±89°.
  • Second angle: longitude – display the inclined angle between the POV line and the vertical plane linked the North and South pole (side). When it is positive, you are facing closer to the East side, while negative for the West side.

Note: In thirdperson mode, all negative angles will be added by 360 degrees.

• Velocity – Should be "speed" from its scalar appearance. Measure the player's net moving speed (those due to props like vehicles and elevator are not counted) in HU s⁻¹.

HU s⁻¹ is HU per second, or HUps, means the distance in HU the object can move in one second.

There is one more infamous statement about the in-game gravity is 800. In fact its unit is HU s⁻², which means an acceleration which lowers your downwards velocity by 800 HU s⁻¹ every second.

Common values in HU

In servers using normal settings, the following would apply:

• Jumping velocity
  • multiplier = 1.0 – +302.00 HU s⁻¹, z direction
  • multiplier = 1.1* – +332.20 HU s⁻¹, z direction
• Gravity – −800.00 HU s⁻², z direction
• Max (terminal) speed – 3500 HU s⁻¹

The following are moving speed values, which depends on the weapon in use, directly proportional. For example, running with M249 is 220 HU s⁻¹, which is 88% of using pistols or knife. Then it will be 114.4 HU s⁻¹ (88% of 130) for walking.

• Running speed – 250.00 HU s⁻¹
• Walking speed – 130.00 HU s⁻¹
• Crouch-moving speed – 85.00 HU s⁻¹
• Crouch-walking speed – 3.32 HU s⁻¹

Zombie's moving speed has a high variance among most ZE servers, thus not listing here.

Lengths related to players:

• Height
  • Standing – 73 HU
  • Crouched – 37 HU
• Eye level
  • Standing – 64 HU above ground
  • Crouched – 47 HU above ground
  • Difference – 17 HU

Ratios to reality

When we can measure virtual objects in a standardized system, they can be kept in reasonable ratios each to each other basically. However, one more thing is needed. A virtual world is simulating the real world on an extent, in order to make sense to users, they should be able to connect with systems the users generally accept too, which are real-life measurements. A Hammer Unit is equivalent to how many inches, or centimeters?

There is only one ratio applied for the values shown after typing cl_showpos 1, which by far the normal players can read. But firstly we take one step further to overview the ratios used in map development.

Ratios for developers

Depending on map or model types, the ratio will change as:

• Maps, architecture and prop models – 0.75 in HU⁻¹, i.e. 1 foot = 16 HU
• Human character models – 1.00 in HU⁻¹, i.e. 1 foot = 12 HU, 1 inch = 1 HU
• Skyboxes – 12.00 in HU⁻¹, i.e. 1 foot = 1 HU

Ratio for players

When playing in a map, all the models and textures will be resized and use the scale of what human character models' using. For normal players it is doubtful to choose among 12 HU or 16 HU to 1 foot, but we can measure the eye level in the player's client. By comparing the z-coordinates of standing and when look straight to the ground (get into the earth by using cheats), the difference is 64 units. Under the map ratio (16 HU to 1 foot), a human player would have an eye level only 4 feet about ground, which make little sense, in contrary to 5 feet and 4 inches for the human model ratio (1 HU to 1 inch). This is an evidence showing the appropriate HU-to-reality ratio.

According to the 1959 definition of 1 yard = 0.9144 meters, the following is the conversion of Hammer Unit to units in Imperial and Metric systems. Exact conversions are marked bold. Corrected to 4 significant figures if not exact.

HU to reality conversions

1 Hammer Unit (HU) = 1 inch (in) 0.1263, 12500/99 links (li) 0.08333, 1/12 feet (ft) 25.4 millimeters (mm) 2.54 centimeters (cm) 0.0254 meters (m)	1 kilo-Hammer Unit (kHU) = 1000 inches 126.3, 12500/99 links 83.33, 250/3 feet 27.78, 250/9 yards (yd) 5.051, 500/99 rods (rd) 1.263, 125/99 chains (ch) 0.1263, 25/198 furlongs (fur) 0.01578, 25/1584 miles (mi) 25.4 meters 0.0254 kilometers
1 square Hammer Unit (HU2) = 1 square inch (sq in) 645.16 square millimeters (mm2) 6.4516 square centimeters (cm2)	1 square kilo-Hammer Unit (kHU2) = 1M square inches 6944, 62500/9 square feet (sq ft) 771.6, 62500/81 square yards (sq yd) 25.51 square rods (sq rd) 1.594 square chains (sq ch) 0.1594 acres 0.0002491 section (sq mi) 645.16 square meters (m2) 0.064516 hectares (ha) 6.4516 × 10−4 square kilometers (km2)
1 cubic Hammer Unit (HU3) = 1 cubic inch (cu in) 16387.064 cubic millimeters (mm3) 16.387064 cubic centimeters (cm3) 0.016387064 liters (L)	1 cubic kilo-Hammer Unit (kHU3) = 1G cubic inches 578700 cubic feet (cu ft) 21430 cubic yards (cu yd) 13.29 acre-foot (acre ft) 3.931 × 10−6 cubic miles (cu mi) 16387064 liters 16387.064 cubic meters (m3) 16.387064 megaliters (ML) 1.6387064 × 10−5 cubic kilometers (km3)

Reality to HU conversions

Units of length 1 in = 1 HU 1 li = 7.92 HU 1 ft = 12 HU 1 yd = 36 HU 1 rd = 198 HU 1 ch = 792 HU 1 fur = 7.92 kHU 1 mi = 63.36 kHU 1 mm = 0.03937 HU (error ~ 0.0002%) 1 cm = 0.3937 HU 1 m = 39.37 HU 1 km = 39.37 kHU	Units of area 1 sq in = 1 HU2 1 sq ft = 144 HU2 1 sq yd = 1296 HU2 1 sq rd = 39204 HU2 1 sq ch = 627264 HU2 1 acre = 6.27264 kHU2 1 section = 4014.4896 kHU2 1 m2 = 1550 HU2 1 hectare = 15.50 kHU2 1 km2 = 1550 kHU2
Units of volume 1 cu in = 1 HU3 1 cu ft = 1728 HU3 1 cu yd = 46656 HU3 1 acre-foot = 75271680 HU3 (= 0.07527168 kHU3) 1 cu mi = 254358.061056 kHU3 1 L = 61.02 HU3 1 m3 = 61020 HU3 1 ML = 0.06102 kHU3 1 km3 = 61020 kHU3

Notes

• 1 mile = 8 furlongs, 1 furlong = 10 chains, 1 chain = 22 yards, 1 yard = 3 feet, 1 foot = 12 inches.
• Also, 1 furlong = 40 rods; 1 chain = 100 links. For reference, 1 rod = 5.5 yards = 16.5 feet.

• 1 section = 1 square mile.
• 1 acre = 1 chain × 1 furlong = 0.792 kHU × 7920 kHU = 6.27264 kHU².
• 1 acre-foot = (1 chain × 1 furlong) × 1 foot = 6.27264 kHU² × 12 HU = 0.07527168 kHU³.

• There are two systems used in the United States: International System and Survey System, which define a foot as 0.9144 meters and 1000/3937 meters respectively. Above units are derived from both systems, but since their difference are small and insignificant in the measurements of Zombie Escape maps, the Survey-derived units are using also the International definition here.