🌱 seeds

Deterministic vector-based RNG seeding for procedural generation.

seeds is a tiny Nim module that lets you turn 2D coordinates into stable random seeds.
Use it to place objects, enemies, trees, loot, structures, and more in infinite worlds without pre-baked maps or global RNG state.

✨ Why Use Vector-Based Seeds?

Many procedural games rely on noise maps (Perlin/Simplex/etc.) to generate terrain.
But terrain noise doesn’t magically decide:

• where plants should grow,
• where enemies spawn,
• what loot a tile drops,
• what weather a region has,
• or how rare structures should appear.

Developers often resort to pre-baked world data, limiting world size and preventing worlds from expanding as the player explores.

seeds solves that by generating deterministic RNG from world coordinates, letting you:

✔️ Save only player-made changes
✔️ Generate everything else on demand
✔️ Expand the game world forever

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📦 Install

nimble install https://github.com/RattleyCooper/seeds

🧬 Usage Example

import vmath
import seeds

# Set the world seed (only do this once)
seeds.seed = 9

let v = ivec2(10, 15)

# Get a unique hash for the vector
echo v.hash()

# Get a consistent value between 0.0 and 1.0 for this location
echo v.saturation

# Create a deterministic RNG for this position
var r = v.initRand()

# Roll deterministic random values
echo r.rand(1.0)

🌲 Use Cases

You can use vector-seeded RNG to procedurally decide:

• Tree type determined by local saturation threshold
• Animal/Enemy spawns determined by seeded range rolls
• Weather events determined by time + tile seed
• Loot rarity determined by compound RNG rolls
• Structure placement determined by seeded checks with sparse outcomes

Combine this with noise maps to create complex worlds without storing anything.

🎯 Collision Testing

This library uses 64-bit multiplication combined with bit-shifting and XOR. It’s not a “perfect hash”, but it performs exceptionally well.

Real test results:

• 178,000,000 vector hashes tested

• Symmetry swaps checked (x,y) vs (y,x)

• 0 collisions found

• Stopped only due to system RAM exhaustion and results being more than good enough to continue testing 😅

This is far beyond what most game worlds will ever require.

In other words: more than safe enough for procedural games.

️⚠️ Limitations

• Hash collisions are mathematically possible (just extremely unlikely).