FoliageCollision

Remarks

[docs/plan/31 § D10]: a foliage type declares a collision shape and an activation radius, and instances within that radius of a physics-relevant entity get a body. Ten thousand static bodies is not a scene, it is a broadphase problem.

⚠ This is a visible behavioural difference and it is stated rather than hidden: a projectile fired at a tree four hundred metres away passes through it. The alternative is a broadphase that degrades for the whole game, and the mitigation available to a project that needs it is to raise ActivationRadius for that type.

⚠ What comes out is a difference, not a set. The caller pools bodies, and a set would make it diff two collections of ten thousand addresses every frame to find the four that changed. Update hands back exactly the four.

Grass never collides: a derived type is never asked, because its instances do not exist between one frame and the next.

Fields and properties (4)

• public IReadOnlySet<FoliageAddress> Active

  Every instance that currently has a body.

• public IReadOnlyList<FoliageAddress> Activated

  What gained one on the last Update.

• public IReadOnlyList<FoliageAddress> Deactivated

  And what lost one.

• public int Count

  How many bodies are wanted right now.

Methods (4)

• public int Update(FoliageVolume volume, IReadOnlyList<Vector3> sources)

  Works out which instances should have a body, and says what changed.

• public void Clear()

  Drops every body, which is what leaving a level does.

• public bool Forget(FoliageAddress address)

  Forgets an address without reporting it, for an instance that no longer exists.

• public int ForgetCell(int type, FoliageCellKey cell)

  Forgets every body in a cell, for a cell an edit rewrote.

Used by (1)

• FoliageCollisionTestsVixen.Foliage.Tests