Refactors the BVH to make it more generic and customizable. Instead of hard coding the system of pairable_mask and pairable_type into the BVH, this information is no longer stored internally, and instead the BVH uses callbacks both for determining whether pairs of objects can pair with each other, and for filtering cull / intersection tests.
In addition, instead of hard coding the number of trees, the BVH now supports up to 32 trees, and each object can supply a tree collision mask to determine which trees it can collide against.
This enables the BVH to scale to either the two or 3 trees needed in physics, and the single tree used without pairing in Godot 4 render tree.
This PR adds a define BVH_EXPAND_LEAF_AABBS which is set, which stores expanded AABBs in the tree instead of exact AABBs.
This makes the logic less error prone when considering reciprocal collisions in the pairing, as all collision detect is now taking place between expanded AABB against expanded AABB, rather than expanded AABB against exact AABB.
The flip side of this is that the intersection tests will now be less exact when expanded margins are set.
All margins are now user customizable via project settings, and take account of collision pairing density to adjust the margin dynamically.
Although the expanded bounds were working in normal use, for moving and growing objects, there was one case which was not dealt with properly - significant shrinkage of exact bounds within an expanded bound.
This PR detects significant shrinkage and forces a new expanded bound to be created.
The pair user data wasn't correctly updated in the BVH from the check
pair callback.
This could lead to crashes when the check caused logical unpairing in
physics, then actual unpairing from the broadphase occured and the
physics server tried to delete an already deleted pointer.
The BVH implementation is not checking collision layers on existing
pairs on move like other physics broadphases do.
This is solved by adding a new call to trigger pair callbacks again so
the physics engine can check layers again (specific to the BVH version,
other broadphase implementations just trigger a move like before).
Dynamic BVH doesn't update the tree anymore when calling set_pairable
with no parameter change.
Also modified Godot Physics broadphase to create objects directly with
pairable (static) set correctly to make use of this optimization for the
BVH broadphase.
Note: Octree broadphase doesn't use this optimization because it forces
an update on move, so passing the proper AABB and static parameters on
creation would cause the tree to update twice.
List of changes:
- Modified bvh class to handle 2D and 3D as a template
- Changes in Rect2, Vector2, Vector3 interface to uniformize template
calls
- New option in Project Settings to enable BVH for 2D Physics (enabled
by default like in 3D)
I had missed a special case check for userdata of two colliding objects being equal. In this case, collisions should not be reported. This is used in the physics to prevent self intersection in composite objects.
When making items visible from the visual server, the collision check is deferred to prevent two identical collision checks when set_pairable is called shortly after.
It turns out that for some items (especially meshes), set_pairable is never called. This PR detects this occurrence and forces a collision check at the end of the routine.
A major feature lacking in the octree was proper support for setting visibility / activation. This meant that invisible objects were still causing lots of processing in the tree unnecessarily.
This PR adds proper support for activation, items are temporarily removed from the tree and collision detection when inactive.
Fix bug whereby AABBs were reused from previous items due to use of a pool, resulting in missed collisions.
Also use full mask collision checks for all cases except generic update.
In the octree collisions are flushed as objects are moved, whereas in the BVH they are usually flushed once per frame.
This was causing problems in the render tree in some rare situations where objects were being created (perhaps deleted and recreated using the same handle in the same frame). This PR flushes the collisions before creating objects, and set_pairable.
set_pairable may not be necessary but it is done for safety until proven not necessary.
Also a small potential for a bug is closed in remove_unordered use.
Change render BVH update scheme from once per update_dirty_instances to a new update_scenarios function called once per draw.
Fix lights not being properly unpaired.
Fixed bug in add_changed_item where AABBs were not being updated due to more than one update per tick.
Calling set_pairable now will update collisions (rather than waiting for the next item_move).
Mask behaviour used for pairing now (hopefully) matches octree.
Complete rewrite of spatial partitioning using a bounding volume hierarchy rather than octree.
Switchable in project settings between using octree or BVH for rendering and physics.
