Units are created by particular unit-producing buildings in Rise of Nations. This page describes how long it takes for units to build.
The basic unit of time in Rise of Nations is a frame, typically 1/15 of a second at normal game speed. In unitrules.xml, each unit has a JOB_TIME value. This value, multiplied by 1.2, is that unit's base build time in frames. For every one of that particular unit already created, the base build time is increased by 7.5 frames. On every frame, the current progress increases by 1. If the current progress, subject to any potential multipliers, equals or exceeds the total number of frames needed to build the unit, then on the next frame the unit will be created (assuming it will not exceed the population cap).
For example, Hoplites have a JOB_TIME of 188. Thus, their base build time in frames is 188 * 1.2 = 225.6. If there are already 3 Hoplites created, then a Hoplites unit under production will need a total of 225.6 + 3*7.5 = 248.1 frames to build. This would be exceeded on the 249th frame, and so the unit would be created on the next (250th) frame. Thus, it takes 250 frames, or 16.7 seconds, to build the 4th Hoplites unit. Some sample needed frames for different units are below:
|Unit||Citizen||Slingers||Hoplites||Bowmen||Light Horse||Cataphract||Horse Archer||Catapult|
This value can be decreased by certain nation powers, patriot abilities, rare resources, and Granary/Smelter technologies. For example, the Romans build Heavy Infantry 10% faster. Thus, the current progress is multiplied by 1.1. For the 6th Hoplites unit, the needed progress is 263.1, and with the Roman bonus, this is reached on the 263.1/1.1 = 239.2 or 240th frame. Thus the Romans would need 241 frames to build their 6th Hoplites unit. These modifiers do not actually change the current progress (which is constant at 1 per frame), but modifies it for display purposes and to compare with the required build time. Thus, the current progress can increase or decrease as conditions change, such as if the President Patriot moves in and out of the building's area.
Notes regarding unit build time:
- In general, production bonuses act as a multiplier on the current progress. For example, the Rare resource Cotton, despite being displayed as reducing production times by 25%, actually increase the current progress by 25%. Different multipliers will multiply with each other.
- An exception is the Granary/Smelter lines of technologies (Herbal Lore and Forage), which decrease the base build time by 10% per tier; thus, fully upgraded, a unit only needs 70% of the calculated base build time (which also means 70% of the 7.5 frames per unit already created).
- The required progress is based on the current number of that particular unit already created (so the number of Hoplites or Javelineers or Atl-Atls do not affect the build progress of Slingers). This means that when that particular unit is dying on the battlefield, the progress of units under construction will noticeably quicken as each existing unit dies. Note that the ramping cost of the unit is calculated differently from this.
- Units under construction do not affect each other's build times. However, even if they were simultaneously started, only one unit will be created first, with the second being affected by that unit's creation and hence delayed.
- The maximum build time is 3 times the base build time of the unit, plus 1 for the unit to be created. For a citizen, with a base build time of 60, the maximum build time is thus 3*60 + 1 = 181 frames. Only citizens and scholars are likely to reach the maximum build time.