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type DurationOverTimeFunc ¶

type DurationOverTimeFunc func(d time.Duration, delta time.Duration) time.Duration

DurationOverTimeFunc is a function that returns a duration after duration d has passed. delta is the duration since the last update (for example, the duration since the last GPU frame.)

type NormalizedDuration ¶

type NormalizedDuration float64

NormalizedDuration is a normalized duration during a longer duration (for example, during a particle's lifetime.) The value is always in the range [0.0,1.0], with 0.0 being the start of the longer duration and 1.0 being the end of the longer duration.

func (t NormalizedDuration) Duration(m time.Duration) time.Duration

type Particle ¶

type Particle struct {
	// contains filtered or unexported fields
}

A Particle is a part of a particle system.

func (p *Particle) Angle() float64

func (p *Particle) Color() color.Color

func (p *Particle) Data() interface{}

func (p *Particle) Kill()

func (p *Particle) Lifetime() time.Duration

func (p *Particle) Position() Vector

func (p *Particle) Scale() Vector

func (p *Particle) System() *ParticleSystem

func (p *Particle) Velocity() Vector

type ParticleColorOverNormalizedTimeFunc ¶

type ParticleColorOverNormalizedTimeFunc func(p *Particle, t NormalizedDuration, delta time.Duration) color.Color

ParticleColorOverNormalizedTimeFunc is a function that returns a color for p after p's duration t has passed. delta is the duration since the last update (for example, the duration since the last GPU frame.)

type ParticleDataOverNormalizedTimeFunc ¶

type ParticleDataOverNormalizedTimeFunc func(old interface{}, t NormalizedDuration, delta time.Duration) interface{}

ParticleDataOverNormalizedTimeFunc is a function that returns arbitrary data for p after p's duration t has passed. The data from previous updates is passed as old and may be modified and returned. For the first update, nil is passed as the old data. delta is the duration since the last update (for example, the duration since the last GPU frame.)

type ParticleDeathFunc ¶

type ParticleDeathFunc func(p *Particle)

ParticleDeathFunc is a function that is called when p has died.

type ParticleSystem ¶

type ParticleSystem struct {
	// MaxParticles limits the total number of particles being alive at a time. When particles die, new particles may be
	// spawned according to EmissionRateOverTime.
	MaxParticles int

	// DataOverLifetime returns arbitrary data for a particle, over its lifetime. This allows to attach data to the particle
	// and act on it later on. The data returned is not used by the system itself.
	DataOverLifetime ParticleDataOverNormalizedTimeFunc

	// DeathFunc is called when a particle has died. This can be used to clean up the data returned by DataOverLifetime
	// (for example, to return the data back into a pool.)
	DeathFunc ParticleDeathFunc

	// UpdateFunc is called to update a particle during its lifetime. This can be used to Particle.Kill it when certain
	// conditions are met.
	UpdateFunc ParticleVisitFunc

	// EmissionRateOverTime returns the emission rate of the system, in particles/second, over the duration of the system.
	//
	// If EmissionRateOverTime is nil, no particles will spawn.
	EmissionRateOverTime ValueOverTimeFunc

	// EmissionPositionOverTime returns the initial position of a particle that is being spawned, over the duration
	// of the system. The position is measured in arbitrary units (for example, in pixels), and is relative to the
	// system's origin.
	//
	// If EmissionPositionOverTime is nil, particles will spawn at the origin.
	EmissionPositionOverTime VectorOverTimeFunc

	// LifetimeOverTime returns the lifetime of a particle that is being spawned, over the duration of the system.
	// After the duration has passed, the particle will die automatically.
	//
	// If LifetimeOverTime is nil, particles will die after 1 second.
	LifetimeOverTime DurationOverTimeFunc

	// VelocityOverLifetime returns a particle's velocity (direction times speed), in arbitrary units per second,
	// over its lifetime.
	//
	// If VelocityOverLifetime is nil, particles will not move.
	VelocityOverLifetime ParticleVectorOverNormalizedTimeFunc

	// ScaleOverLifetime returns a particle's scale (size multiplier), over its lifetime.
	//
	// If ScaleOverLifetime is nil, particles will use (1.0,1.0).
	ScaleOverLifetime ParticleVectorOverNormalizedTimeFunc

	// ColorOverLifetime returns a particle's color, over its lifetime.
	//
	// If ColorOverLifetime is nil, particles will use color.White.
	ColorOverLifetime ParticleColorOverNormalizedTimeFunc

	// RotationOverLifetime returns a particle's angular velocity, in radians, over its lifetime.
	//
	// If RotationOverLifetime is nil, particles will not rotate.
	RotationOverLifetime ParticleValueOverNormalizedTimeFunc
	// contains filtered or unexported fields
}

A ParticleSystem simulates a number of particles. Various functions are called to customize the behavior of the particles.

The position of a particle is always relative to its system's origin. In other words, a particle system maintains its own frame of reference. Particles are not simulated in "world space." However, when particles are actually drawn on screen, the origin of the particle system can be moved freely, thus emulating a simulation in world space.

func NewSystem() *ParticleSystem

func (s *ParticleSystem) Duration(now time.Time) time.Duration

func (s *ParticleSystem) ForEachParticle(f ParticleVisitFunc, now time.Time)

func (s *ParticleSystem) NumParticles() int

func (s *ParticleSystem) Reset()

func (s *ParticleSystem) Spawn(num int)

func (s *ParticleSystem) Update(now time.Time)

type ParticleValueOverNormalizedTimeFunc ¶

type ParticleValueOverNormalizedTimeFunc func(p *Particle, t NormalizedDuration, delta time.Duration) float64

ParticleValueOverNormalizedTimeFunc is a function that returns a value for p after p's duration t has passed. delta is the duration since the last update (for example, the duration since the last GPU frame.)

type ParticleVectorOverNormalizedTimeFunc ¶ added in v0.2.0

type ParticleVectorOverNormalizedTimeFunc func(p *Particle, t NormalizedDuration, delta time.Duration) Vector

ParticleVectorOverNormalizedTimeFunc is a function that returns a vector for p after p's duration t has passed. delta is the duration since the last update (for example, the duration since the last GPU frame.)

type ParticleVisitFunc ¶

type ParticleVisitFunc func(p *Particle, t NormalizedDuration, delta time.Duration)

ParticleVisitFunc is a function that is called for p after p's duration t has passed, when looping over all particles in the system using ParticleSystem.ForEachParticle. delta is the duration since the last update (for example, the duration since the last GPU frame.)

type ValueOverTimeFunc ¶

type ValueOverTimeFunc func(d time.Duration, delta time.Duration) float64

ValueOverTimeFunc is a function that returns a value after duration d has passed. delta is the duration since the last update (for example, the duration since the last GPU frame.)

type Vector ¶ added in v0.2.0

type Vector struct {
	X float64
	Y float64
}

A Vector is a geometric entity that has a direction and a length.

func (v Vector) Add(v2 Vector) Vector

func (v Vector) Magnitude() float64

func (v Vector) Multiply(d float64) Vector

func (v Vector) Normalize() Vector

func (v Vector) TryNormalize() (Vector, bool)

type VectorOverTimeFunc ¶ added in v0.2.0

type VectorOverTimeFunc func(d time.Duration, delta time.Duration) Vector

VectorOverTimeFunc is a function that returns a vector after duration d has passed. delta is the duration since the last update (for example, the duration since the last GPU frame.)