Cauldron2D.Particles (Cauldron2D v0.1.3)

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Short-lived sprites — sparks, debris, smoke — with a cap on how many exist at once.

particles =
  Cauldron2D.Particles.new(300)
  |> Cauldron2D.Particles.spawn([%{art: :spark, pos: {x, y}, vel: {vx, vy}, ttl: 0.4}])
  |> Cauldron2D.Particles.step(dt, fields: gravity, drag: 0.5)

Cauldron2D.Particles.movers(particles, {-0.5, -0.5})

A particle is %{art: art, pos: {x, y}, vel: {vx, vy}, ttl: seconds}. When spawning would exceed the cap, the oldest particles go first.

Summary

Types

particle()
t()

Functions

count(particles)

How many particles are alive.

movers(particles, arg \\ {0.0, 0.0})

The particles as {art, {x, y}} movers, oldest first, each position shifted by offset.

new(cap)

An empty set holding at most cap particles.

spawn(particles, new_items)

Add particles, dropping the oldest when the cap is exceeded.

step(particles, dt, opts \\ [])

Move every particle for dt seconds and drop those whose time is up.

Types

particle()

@type particle() :: %{
  art: term(),
  pos: Cauldron2D.Body.point(),
  vel: Cauldron2D.Body.point(),
  ttl: number()
}

t()

@type t() :: %Cauldron2D.Particles{cap: pos_integer(), items: [particle()]}

Functions

count(particles)

@spec count(t()) :: non_neg_integer()

How many particles are alive.

movers(particles, arg \\ {0.0, 0.0})

@spec movers(t(), Cauldron2D.Body.point()) :: [{term(), Cauldron2D.Body.point()}]

The particles as {art, {x, y}} movers, oldest first, each position shifted by offset.

The offset is what turns a particle's centre into the top-left corner a sprite is drawn from; {-0.5, -0.5} centres a one-tile sprite.

new(cap)

@spec new(pos_integer()) :: t()

An empty set holding at most cap particles.

spawn(particles, new_items)

@spec spawn(t(), [particle()]) :: t()

Add particles, dropping the oldest when the cap is exceeded.

step(particles, dt, opts \\ [])

@spec step(t(), number(), keyword()) :: t()

Move every particle for dt seconds and drop those whose time is up.

Options