Class: RGame::Engine::CollisionSystem

Inherits:
Object
  • Object
show all
Defined in:
lib/rgame/engine/collision_system.rb

Overview

The actor-facing collision system: moves any actor by a delta, resolving its collision box (not its sprite) against the tiles via TileCollision, then clamping the box inside the world as a backstop. Reusable by the player and any NPC.

Instance Method Summary collapse

Constructor Details

#initialize(tile_collision:, world_width:, world_height:) ⇒ CollisionSystem

Returns a new instance of CollisionSystem.



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# File 'lib/rgame/engine/collision_system.rb', line 11

def initialize(tile_collision:, world_width:, world_height:)
  @tiles = tile_collision
  @world_width = world_width
  @world_height = world_height
end

Instance Method Details

#move(actor, dx, dy) ⇒ Object

Move actor by (dx, dy), writing the resolved position back to it.



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# File 'lib/rgame/engine/collision_system.rb', line 18

def move(actor, dx, dy)
  box = actor.collision_box
  # Read the box AABB into locals directly rather than via box.aabb, which would
  # allocate an Array on this per-frame path.
  bx = actor.x + box.offset_x
  by = actor.y + box.offset_y
  bw = box.width
  bh = box.height

  bx = @tiles.resolve_x(bx, by, bw, bh, dx)
  by = @tiles.resolve_y(bx, by, bw, bh, dy)

  # Clamp the box inside the world. Floor each upper bound at 0 without a [span, 0]
  # array (this runs per actor per frame).
  max_x = @world_width - bw
  max_x = 0 if max_x.negative?
  max_y = @world_height - bh
  max_y = 0 if max_y.negative?
  bx = bx.clamp(0.0, max_x.to_f)
  by = by.clamp(0.0, max_y.to_f)

  actor.x = bx - box.offset_x
  actor.y = by - box.offset_y
end