Class: RGame::Engine::Components::CameraFollow

Inherits:
RGame::Engine::Component show all
Defined in:
lib/rgame/engine/components/camera_follow.rb

Overview

Points a camera at the node it is attached to.

player_node.add_component(CameraFollow.new(camera: players.primary.camera))

Ownership and behaviour are different questions

The camera cannot be owned by a node in the world — with several viewers there are several cameras, and a world that holds one has to know how many times it is being drawn. But deciding where a camera points is exactly a per-node concern, so it belongs here: the player owns the camera, and a component in the world moves it.

That also makes "player two's camera follows player two" nothing more than attaching this to their node with their camera.

offset_x / offset_y shift the point being centred on, for a node whose origin is not what should be in the middle of the screen — a bottom-anchored sprite usually wants its feet, not its head.

Instance Attribute Summary

Attributes inherited from RGame::Engine::Component

#node

Instance Method Summary collapse

Methods inherited from RGame::Engine::Component

#context, #control, #draw, #on_attach, #on_detach, #sweep_freed

Methods included from Signal::DSL

#signal

Constructor Details

#initialize(camera:, offset_x: 0.0, offset_y: 0.0) ⇒ CameraFollow

Returns a new instance of CameraFollow.



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# File 'lib/rgame/engine/components/camera_follow.rb', line 25

def initialize(camera:, offset_x: 0.0, offset_y: 0.0)
  super()
  @camera = camera
  @offset_x = offset_x
  @offset_y = offset_y
end

Instance Method Details

#update(_dt) ⇒ Object

Reads the absolute origin resolved at the top of this node's update, so the camera trails the node's own movement by one step (a couple of pixels at walking speed). That is deliberate and uniform: everything drawn through this camera trails equally, so nothing drifts apart on screen, and the alternative — re-resolving here — would put this component's ordering among its siblings on show.



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# File 'lib/rgame/engine/components/camera_follow.rb', line 38

def update(_dt)
  @camera.center_on(node.abs_x + @offset_x, node.abs_y + @offset_y)
end