Class: RGame::Engine::Path

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

Overview

An ordered polyline of waypoints an entity walks along — the "road" of a tower defense level. Pure data: it holds the waypoints and the precomputed per-segment lengths, so a follower walking it at runtime allocates nothing.

Waypoints are stored flat (x0, y0, x1, y1, …) in one contiguous array rather than a pair-object per point, and read back through scalar accessors (x_at/y_at), so neither construction shape nor traversal leaks per-waypoint Arrays onto the hot path. A follower (see Components::PathFollow) reads segments by index and interpolates itself; Path never returns a coordinate pair.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(points) ⇒ Path

points is an Array of [x, y] waypoint pairs in walk order (construction-time, so the pair Arrays are fine here). At least two are required — a path with one point has nowhere to walk.

Raises:

  • (ArgumentError) 


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# File 'lib/rgame/engine/path.rb', line 20

def initialize(points)
  raise ArgumentError, 'a Path needs at least two waypoints' if points.length < 2

  @coords = points.flatten.freeze
  @count = points.length
  @segment_lengths, @length = build_segments
end

Instance Attribute Details

#count ⇒ Object (readonly)

Returns the value of attribute count.



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# File 'lib/rgame/engine/path.rb', line 15

def count
  @count
end

#length ⇒ Object (readonly)

Returns the value of attribute length.



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# File 'lib/rgame/engine/path.rb', line 15

def length
  @length
end

Instance Method Details

#distance_to(x, y) ⇒ Object

Shortest distance from the point (x, y) to the polyline — e.g. how far a spot is from the road, so a tower-defense level can mask placement cells that sit on it. Pure scalar maths, allocation-free.



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# File 'lib/rgame/engine/path.rb', line 39

def distance_to(x, y)
  min = Float::INFINITY
  (@count - 1).times do |i|
    d = segment_distance(x, y, x_at(i), y_at(i), x_at(i + 1), y_at(i + 1))
    min = d if d < min
  end
  min
end

#segment_length(index) ⇒ Object

Length of the segment from waypoint i to waypoint i + 1. There are count - 1 segments, indexed 0..count-2.



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# File 'lib/rgame/engine/path.rb', line 34

def segment_length(index) = @segment_lengths[index]

#x_at(index) ⇒ Object

World coordinates of waypoint i (0-based), as scalars (no allocation).



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# File 'lib/rgame/engine/path.rb', line 29

def x_at(index) = @coords[index * 2]

#y_at(index) ⇒ Object 



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# File 'lib/rgame/engine/path.rb', line 30

def y_at(index) = @coords[(index * 2) + 1]