Class: SFML::ParticleSystem

Inherits:
Object
  • Object
show all
Defined in:
lib/sfml/graphics/particle_system.rb

Overview

A pool-backed particle emitter built on top of SFML::VertexArray. Each particle is two triangles (a quad) so a single CSFML draw call ships thousands at once.

class Sparks < SFML::ParticleSystem
def emit_one
  angle = rand(0.0..2 * Math::PI)
  speed = rand(80.0..200.0)
  spawn(
    position:  @origin,
    velocity:  SFML::Vector2.new(Math.cos(angle), Math.sin(angle)) * speed,
    lifetime:  0.8,
    color:     SFML::Color.new(255, 200, 50),
    size:      4,
  )
end
end

sparks = Sparks.new(max: 500)

def update(dt)
5.times { sparks.emit_one } if mouse_down?
sparks.update(dt)
end

def draw
window.draw(sparks)
end

Particles fade linearly from full alpha at spawn to zero alpha at lifetime. Override #update_particle(p, dt) to apply gravity, drag, custom colour curves, etc.

Acceleration: pass gravity: to the constructor for the common case (px/s² added to velocity every frame). For richer behaviour, subclass and override.

Defined Under Namespace

Classes: Particle

Constant Summary collapse

DEFAULT_GRAVITY =

No gravity by default [0.0, 0.0].

[0.0, 0.0].freeze

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(max: 1000, gravity: DEFAULT_GRAVITY, texture: nil) ⇒ ParticleSystem

Returns a new instance of ParticleSystem.



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# File 'lib/sfml/graphics/particle_system.rb', line 57

def initialize(max: 1000, gravity: DEFAULT_GRAVITY, texture: nil)
  @max          = Integer(max)
  @gravity_x    = Float(gravity[0])
  @gravity_y    = Float(gravity[1])
  @texture      = texture
  @particles    = []
  @vertex_array = VertexArray.new(:triangles)
end

Instance Attribute Details

#particles ⇒ Object (readonly)

The particles, texture components.



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# File 'lib/sfml/graphics/particle_system.rb', line 67

def particles
  @particles
end

#texture ⇒ Object (readonly)

The particles, texture components.



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# File 'lib/sfml/graphics/particle_system.rb', line 67

def texture
  @texture
end

Instance Method Details

#clear ⇒ Object

Drop every live particle.



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# File 'lib/sfml/graphics/particle_system.rb', line 100

def clear
  @particles.clear
  self
end

#draw_on(target, states_ptr = nil) ⇒ Object

Drawable interface — rebuilds the VertexArray and forwards.



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# File 'lib/sfml/graphics/particle_system.rb', line 133

def draw_on(target, states_ptr = nil)
  _rebuild_vertex_array
  @vertex_array.draw_on(target, states_ptr)
end

#empty? ⇒ Boolean

true if empty.

Returns:

  • (Boolean) 


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# File 'lib/sfml/graphics/particle_system.rb', line 71

def empty? = @particles.empty?
# `true` if full.

#full? ⇒ Boolean

true if full.

Returns:

  • (Boolean) 


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# File 'lib/sfml/graphics/particle_system.rb', line 73

def full?  = @particles.size >= @max

#size ⇒ Object

Returns the size.



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# File 'lib/sfml/graphics/particle_system.rb', line 69

def size = @particles.size
# `true` if empty.

#spawn(position:, velocity: [0, 0], lifetime: 1.0, color: Color.white, size: 4) ⇒ Object

Spawn a new particle. Silently dropped if the pool is full (better than reallocating; users can size up max:).

Parameters:

  • position (Vector2, Array) —

    world coords

  • velocity (Vector2, Array) (defaults to: [0, 0]) —

    px/s

  • lifetime (Numeric) (defaults to: 1.0) —

    seconds

  • color (SFML::Color) (defaults to: Color.white)
  • size (Numeric) (defaults to: 4) —

    half-side of the quad in pixels



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# File 'lib/sfml/graphics/particle_system.rb', line 83

def spawn(position:, velocity: [0, 0], lifetime: 1.0, color: Color.white, size: 4)
  return if full?

  px, py = _xy(position)
  vx, vy = _xy(velocity)

  @particles << Particle.new(
    Float(px), Float(py),
    Float(vx), Float(vy),
    0.0, Float(lifetime),
    color.r, color.g, color.b, color.a,
    Float(size),
  )
  self
end

#update(dt) ⇒ Object

Advance all particles by dt and remove dead ones.



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# File 'lib/sfml/graphics/particle_system.rb', line 106

def update(dt)
  seconds = dt.is_a?(Time) ? dt.as_seconds : Float(dt)
  gx, gy  = @gravity_x, @gravity_y

  @particles.each do |p|
    next unless p.alive?

    # Gravity + integration. Subclasses can override
    # update_particle to layer additional forces / drag.
    p.vx += gx * seconds
    p.vy += gy * seconds
    p.x  += p.vx * seconds
    p.y  += p.vy * seconds
    p.age += seconds
    update_particle(p, seconds)
  end

  @particles.delete_if { |p| !p.alive? }

  self
end

#update_particle(_particle, _dt) ⇒ Object

Hook: tweak a particle's state. Default does nothing; override for drag, attractors, colour curves over lifetime, etc.



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# File 'lib/sfml/graphics/particle_system.rb', line 130

def update_particle(_particle, _dt); end