While checking on how Ent_AddComponent behaved (I don't remember what I
was looking for, though), I realized that instead of treating adding the
same component to an entity as an error, Ent_AddComponent should just
return the existing component.
This puts the hierarchy (transform) reference, animation, visibility,
renderer, active, and old_origin data in separate components. There are
a few bugs (crashes on grenade explosions in gl/glsl/vulkan, immediately
in sw, reasons known, missing brush models in vulkan).
While quake doesn't really need an ECS, the direction I want to take QF
does, and it does seem to have improved memory bandwidth a little
(uncertain). However, there's a lot more work to go (especially fixing
the above bugs), but this seems to be a good start.
That does feel a little redundant, but I think the System in ECS is
referring to the systems that run on the components, while the other
system is the support code for the ECS. Anyway...
This is based heavily on the information provided by @skipjack in his
github blog about EnTT. Currently, entity recycling and sparse arrays
for component pools have been implemented, and adding components to an
entity has been tested.
This is the beginning of adding ECS to QF. While the previous iteration
of hierarchies was a start in the direction towards ECS, this pulls most
of the 3d-specific transform stuff out of the hierarchy "objects",
making all the matrices and vectors/quaternions actual components (in
the ECS sense). There's more work to be done with respect to the
transform and entity members of hierarchy_t (entity should probably go
away entirely, and transform should become hierref_t (or whatever its
final name becomes), but I wanted to get things working sooner than
later.
The motivation for the effort was to allow views to use hierarchy_t,
which should be possible once I get entity and transform sorted out.
I am really glad I already had automated tests for hierarchies, as
things proved to be a little tricky to get working due to forgetting why
certain things were there.
