How system data is extracted from the galaxy and system seeds
Famously, Elite's galaxy and system data is generated procedurally, using a set of three 16-bit seed numbers and the Tribonnaci series to generate entire galaxies of systems like this:
Each of these systems has its own set of seeds, which can be calculated using a simple process called "twisting". For details of this process and how it can be used to generate 2048 different sets of seeds for the 256 systems in each of the game's eight galaxies, see the deep dive on twisting the system seeds.
Each set of seeds contains all the data for one specific system. In this article we'll take an overview of everything that's captured in the seeds, and for more detailed analysis you can read the deep dives on generating system data, generating system names and market item prices and availability.
Structure of the system seeds
-----------------------------
The seeds are stored in two places: QQ15 contains the seeds for the currently selected system in the system chart, and QQ21 contains the seeds for system 0 in the current galaxy.
Seeds for each system in the galaxy can be generated from the seeds for system 0 in QQ21 by repeatedly twisting the seeds for system 0 - see the deep dive on twisting the system seeds for details.
The seeds are stored as three little-endian 16-bit numbers, so the low (least significant) byte is first followed by the high (most significant) byte, in the same way that the 6502 stores 16-bit addresses. That means if the seeds are s0, s1 and s2, they are stored like this:
| Seed | Low byte | High byte |
|---|---|---|
| s0 | QQ15 | QQ15+1 |
| s1 | QQ15+2 | QQ15+3 |
| s2 | QQ15+4 | QQ15+5 |
Throughout this documentation, we denote the low byte of s0 as s0_lo and the high byte as s0_hi, and so on for s1_lo, s1_hi, s2_lo and s2_hi.
Given a set of seeds for a specific system, we can extract all the system data from those seeds. Here's a summary of which bits in which seeds are used to generate the various bits of data in the universe. The routine names where these data are generated are shown on the right.
s0_hi s0_lo s1_hi s1_lo s2_hi s2_lo
76543210 76543210 76543210 76543210 76543210 76543210
^------- Species is human TT25
^^^----------- Species adjective 1 TT25
^^^-------------- Species adjective 2 TT25
^^----------------^^--------------------------- Species adjective 3 TT25
^^--------- Species type TT25
^^^^^^^^--------------^^^^--------- Average radius TT25
^^^--------------------- Government type TT24
^^^--------------------------------------------- Prosperity level TT24
^----------------------------------------------- Economy type TT24
^^--------------------------- Tech level TT24
^^^^^^^^--------------------------- Galactic x-coord TT24
^^^^^^^^--------------------------------------------- Galactic y-coord TT24
^-^^^^ Long-range dot size TT22
^ Short-range size TT23
^------------------------------------------ Name length cpl
^^^^^--------- Name token (x4) cpl
^^^--------------------------------------------- Planet distance SOLAR
^^^--------------------------- Sun distance SOLAR
^^--------- Sun x-y offset SOLAR
76543210 76543210 76543210 76543210 76543210 76543210
s0_hi s0_lo s1_hi s1_lo s2_hi s2_lo
An example
----------
Let's take a look at how this works with the starting system of Lave, which has a Data on System screen like this:
at this location on the Long-range Chart (where it's shown as a two-pixel dash):
and this appearance on the Short-range Chart (where it's shown as a medium star):
Lave's seeds are as follows:
s0_hi s0_lo s1_hi s1_lo s2_hi s2_lo
10101101 00111000 00010100 10011100 00010101 00011101
^------- Species is human TT25
^^^----------- Species adjective 1 TT25
^^^-------------- Species adjective 2 TT25
^^----------------^^--------------------------- Species adjective 3 TT25
^^--------- Species type TT25
^^^^^^^^--------------^^^^--------- Average radius TT25
^^^--------------------- Government type TT24
^^^--------------------------------------------- Prosperity level TT24
^----------------------------------------------- Economy type TT24
^^--------------------------- Tech level TT24
^^^^^^^^--------------------------- Galactic x-coord TT24
^^^^^^^^--------------------------------------------- Galactic y-coord TT24
^-^^^^ Long-range dot size TT22
^ Short-range size TT23
^------------------------------------------ Name length cpl
^^^^^--------- Name token (x4) cpl
^^^--------------------------------------------- Planet distance SOLAR
^^^--------------------------- Sun distance SOLAR
^^--------- Sun x-y offset SOLAR
10101101 00111000 00010100 10011100 00010101 00011101
s0_hi s0_lo s1_hi s1_lo s2_hi s2_lo
We interpret these seeds as follows:
| Data | Seed bits | Result |
|---|---|---|
| Species is human | %0 | Human Colonials |
| Average radius | %00010100 %0101 | (%0101 + 11) * 256 + %00010100 = 4116 Shown as 4116 km |
| Government type | %011 | Dictatorship |
| Prosperity level | %101 | Rich |
| Economy type | %1 | Agricultural |
| Tech level | %00 | ~%101 + %00 + ceiling(%011 / 2) = 4 Shown as Tech level 5 |
| Population | - | 4 * 4 + %101 + %011 + 1 = 25 Shown as 2.5 billion |
| Productivity | - | (~%101 + 3) * (%011 + 4) * 25 * 8 = 7000 Shown as 7000 M CR |
| Galactic x-coord | %00010100 | 20 |
| Galactic y-coord | %10101101 | 173 >> 1 = 86 |
| Long-range dot size | %x0x11101 | %x0x11101 OR %01010000 = %01011101 = 93 Shown as a single-height two-pixel dot |
| Short-range size | %1 | %1 + 2 + no carry from cpl = 3 Shown as a medium-sized star |
| Name length | %0 | Generate three pairs of letters for name |
| Name token (x4) | %10101 %10110 %00000 %01100 | 128 + %10101 = 149 ("LA") 128 + %10110 = 150 ("VE") %00000 = 0 = skip Ignore fourth pair |
| Planet distance | %101 | (%101 + 6 + bit 0 of FIST) >> 1 = %1011 >> 1 if bit 0 of FIST was 0 so planet spawns at: x = -(2 0 0) y = -(2 0 0) z = (5 0 0) = %1100 >> 1 if bit 0 of FIST was 1 so planet spawns at: x = (3 0 0) y = (3 0 0) z = (6 0 0) |
| Sun distance | %100 | %101 OR %10000001 = %10000101 = -5 so sun spawns at: z = -(5 0 0) |
| Sun x-y offset | %01 | So sun spawns at: x = (1 0 0) y = (1 0 0) |