Some things Veloren does differently

Veloren, a voxel game, sets itself apart from other MMOs by utilizing an Entity Component System (ECS) instead of a traditional object-oriented class hierarchy. This choice allows Veloren to scale better, with the ability to handle over 500 players connected on a 48-thread server while consuming only 50% of core utilization. Unlike most MMOs that either reduce gameplay scope or shard players across different world spaces to achieve such numbers, Veloren benefits from a more efficient architecture.

One unexpected consequence of using ECS is the flexibility it provides in handling polymorphism. In a traditional game engine, different entities are separated by compile-time bifurcation at the type level, with polymorphism being an optional feature. However, in Veloren's ECS, polymorphism is the default, leading to some interesting side effects.

For instance, a bug once allowed players to pick up other players when nearby due to an error in implementing loot. Additionally, when implementing mounts, faulty cycle detection and control passthrough logic resulted in players creating enormous towers of entities riding each other or even creating mount cycles, resulting in amusing chaos in the game world.

Veloren's approach to player characters and NPCs is unique as well. Both are modeled in the same way, interacting with the physics engine similarly and having the same movement control options. While NPCs cannot teleport or phase through blocks, they are governed by the same movement controller code as players. Furthermore, both share the same skill tree and experience system, even having the same sound effects for NPCs leveling up.

In terms of world generation, Veloren takes a different approach compared to many other voxel games. Instead of generating the world on-the-fly as players explore, Veloren pre-generates the entire world at a lower resolution during startup and then refines it using interpolation and noise-based techniques as players get closer. This up-front generation step enables Veloren to support complex features like flowing rivers that always follow a downhill path, which would be difficult to implement with local constraint solving only.

By performing simulations before the game starts, Veloren can create more interesting and consistent world features.