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.
Hierarchies are now much closer to being more general in that they are
not tied to 3d transforms. This is a major step to moving the whole
entity/transform system into an ECS.
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.
The main goal was to get visframe out of mnode_t to make it thread-safe
(each thread can have its own visframe array), but moving the plane info
into mnode_t made for better data access patters when traversing the bsp
tree as the plane is right there with the child indices. Nicely, the
size of mnode_t is the same as before (64 bytes due to alignment), with
4 bytes wasted.
Performance-wise, there seems to be very little difference. Maybe
slightly slower.
The unfortunate thing about the change is the plane distance is negated,
possibly leading to some confusion, particularly since the box and
sphere culling functions were affected. However, this is so point-plane
distance calculations can be done with a single 4d dot product.
The root transform of each hierarchy can be extracted from the first
transform of the list in the hierarchy, so no information is lost. The
main reason for the change is I discovered (obvious in hindsight) that
deleting root transforms was O(n) due to keeping them in an array, thus
the use of a linked list (I don't expect a hierarchy to be in more than
one such list), and I didn't want the transforms to be in a linked list.
Since transforms now know the scene to which they belong, and they know
when they are root and when not, getting the transform code to manage
the scene roots is the best way to keep the list of root transforms
consistent.
This actually has at least two benefits: the transform id is managed by
the scene and thus does not need separate management by the Ruamoko
wrapper functions, and better memory handling of the transform objects.
Another benefit that isn't realized yet is that this is a step towards
breaking the renderers free of quake and quakeworld: although the
clients don't actually use the scene yet, it will be a good place to
store the rendering information (functions to run, etc).
