Module: Doom::Game::Geometry

Defined in:
lib/doom/game/geometry.rb

Overview

Shared 2D geometry for the simulation. These three helpers were copy-pasted across combat, monster AI, player physics, world and sector actions (the last under the name point_line_dist); consolidated here so line-of-sight, collision and use-line checks share one definition.

Pure functions of their arguments -- no state, no RNG, no wall clock -- so they stay deterministic and every peer computes the same result.

Class Method Summary collapse

Class Method Details

.line_circle_intersect?(x1, y1, x2, y2, cx, cy, radius) ⇒ Boolean

Does the segment (x1,y1)->(x2,y2) pass within radius of the circle centred at (cx,cy)? The collision test for a body of that radius sliding against a wall.

Returns:

  • (Boolean) 


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# File 'lib/doom/game/geometry.rb', line 36

def line_circle_intersect?(x1, y1, x2, y2, cx, cy, radius)
  dx = cx - x1
  dy = cy - y1
  line_dx = x2 - x1
  line_dy = y2 - y1
  line_len_sq = (line_dx * line_dx) + (line_dy * line_dy)
  return false if line_len_sq.zero?

  t = (((dx * line_dx) + (dy * line_dy)).to_f / line_len_sq).clamp(0.0, 1.0)
  closest_x = x1 + (t * line_dx)
  closest_y = y1 + (t * line_dy)
  dist_sq = ((cx - closest_x)**2) + ((cy - closest_y)**2)
  dist_sq < radius * radius
end

.point_to_segment_distance(px, py, x1, y1, x2, y2) ⇒ Object

Shortest distance from point (px,py) to the segment (x1,y1)->(x2,y2), clamped to the segment ends. Used for use-line and trigger proximity.



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# File 'lib/doom/game/geometry.rb', line 53

def point_to_segment_distance(px, py, x1, y1, x2, y2)
  dx = px - x1
  dy = py - y1
  line_dx = x2 - x1
  line_dy = y2 - y1
  line_len_sq = (line_dx * line_dx) + (line_dy * line_dy)
  return Math.sqrt((dx * dx) + (dy * dy)) if line_len_sq.zero?

  t = (((dx * line_dx) + (dy * line_dy)).to_f / line_len_sq).clamp(0.0, 1.0)
  closest_x = x1 + (t * line_dx)
  closest_y = y1 + (t * line_dy)
  Math.sqrt(((px - closest_x)**2) + ((py - closest_y)**2))
end

.segments_intersect?(ax1, ay1, ax2, ay2, bx1, by1, bx2, by2) ⇒ Boolean

Do the open segments A (ax1,ay1)->(ax2,ay2) and B (bx1,by1)->(bx2,by2) cross? Used for line-of-sight and hitscan against walls. Parallel or barely-crossing segments (tiny determinant) count as no intersection.

Returns:

  • (Boolean) 


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# File 'lib/doom/game/geometry.rb', line 18

def segments_intersect?(ax1, ay1, ax2, ay2, bx1, by1, bx2, by2)
  d1x = ax2 - ax1
  d1y = ay2 - ay1
  d2x = bx2 - bx1
  d2y = by2 - by1
  denom = (d1x * d2y) - (d1y * d2x)
  return false if denom.abs < 0.001

  dx = bx1 - ax1
  dy = by1 - ay1
  t = ((dx * d2y) - (dy * d2x)).to_f / denom
  u = ((dx * d1y) - (dy * d1x)).to_f / denom
  t > 0.0 && t < 1.0 && u >= 0.0 && u <= 1.0
end