The cosmos common contains state that is not tied to any particular entity or component, but is still required by the solvers.
The solvers, however, cannot modify it. It can only ever be altered during the content creation stage, e.g. in editor.

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Overview

There are certain examples of state that is better held common for all game objects.
For example: if there exist 200 entities named “Road”, it makes no sense to store 2 hundred std::strings containing a value of “Road”.
It would be better if those 200 entities could share a single std::string that they could refer to by a simple identifier.

So, for each such entity, we store a flavour identifier inside its entity_solvable_meta, which is a simple integer.
Then we store a map from the type identifier into an entity flavour object (that is a part of the cosmos common significant) that contains the corresponding std::string.

This has several advantages:

  • Less state to be synchronized through the network.
  • Changing the name from “Road” to “EvenBetterRoad” for all road entities involves a single reassignment in the map, instead of iterating through all entities.

Fields

Similarly to cosmos solvable, the cosmos common consists of two parts:

  • Significant

    Represents the part of the cosmos common that is significant. It holds:

    • All logical assets.
    • All entity flavours.
    • Descriptions of spells and their properties (e.g. PE points needed to cast).
    • Numerical settings for some stateless systems (e.g. epsilons for visibility and pathfinding systems).
    • Many more.

  • Inferred

    The storage of all caches that are at any time regenerable from the contents of the significant field.

    • A map of names into corresponding type identificators.

Notes

Implementation note: always ensure that the cosmos solvable is reinferred after reinferring the cosmos common. That is because, if the order of operation was reversed…
…well, actually, nothing bad should happen. That is because physics world caches will have a flag of whether a particular b2Shape belongs to an entity, and thus should be freed on destruction, or if it belongs to the common, and should not touch it at all. However: it might be the case that a b2PolygonShape or so might end up at a completely different address then from before reinference. Better safe then sorry.