Layers and masks

Generated from engine/collision/collision_layer.h at 862e08b. The text under each declaration is the header's own comment, word for word. About the reference says how these pages are made.

Browse the collision module

#include "engine/collision/collision_layer.h" · namespace labrador

CollisionLayer

using CollisionLayer = std::uint32_t;

Which group an object belongs to: exactly one bit, set by the game.

The engine assigns no meaning to any bit and never compares one to a named constant - there are no named constants here, and that absence is the point. An enum of one game's nouns reachable from the collision interface would mean the engine could not be handed a second game without either editing the enum or lying to it (T1).

CollisionMask

using CollisionMask = std::uint32_t;

Which layers an object responds to. Zero means "nothing, right now" - a legitimate and useful answer, and the one a dead player gives.

CollisionTag

using CollisionTag = std::uint32_t;

The game's own classification, carried through the engine untouched.

Nothing in engine/ reads this. It exists so a response can recover what it hit without the engine having to know the vocabulary: the game casts its enum in on one side and out on the other. That is the whole of "the engine decides whether things collide; the game decides what it means" (PHILOSOPHY, Collision).

layers_collide

constexpr bool layers_collide(CollisionLayer a_layer, CollisionMask a_mask,
  CollisionLayer b_layer, CollisionMask b_mask);

Two objects are a candidate pair when each one's layer is in the other's mask.

Both directions must agree, so either side can veto. That symmetry is what makes the answer a property of the pair: a one-sided filter can pass (a, b) and fail (b, a), and which response runs then comes down to which object a loop happens to be iterating.

In the samples and tests

The files that include this header directly. A file can also reach it through another header.

• tests/collision/ broad_phase_tests.cpp