public bool Update()
{
_elapsedTime += Time.DeltaTime;
// fading block
if (_elapsedTime > _fadeDelay && _elapsedTime < _fadeDuration + _fadeDelay)
{
var t = Mathf.Map01(_elapsedTime, 0f, _fadeDelay + _fadeDuration);
ColorExt.Lerp(ref _initialColor, ref _targetColor, out _renderColor, t);
}
else if (_elapsedTime >= _fadeDuration + _fadeDelay)
{
return(true);
}
return(false);
}
/// <summary>
/// updates the particle. Returns true when the particle is no longer alive
/// </summary>
/// <param name="emitterConfig">Emitter config.</param>
public bool Update(ParticleEmitterConfig emitterConfig, ref ParticleCollisionConfig collisionConfig,
Vector2 rootPosition)
{
// PART 1: reduce the life span of the particle
_timeToLive -= Time.DeltaTime;
// if the current particle is alive then update it
if (_timeToLive > 0)
{
// only update the particle position if it has not collided. If it has, physics takes over
if (!_collided)
{
// if maxRadius is greater than 0 then the particles are going to spin otherwise they are affected by speed and gravity
if (emitterConfig.EmitterType == ParticleEmitterType.Radial)
{
// PART 2: update the angle of the particle from the radius. This is only done if the particles are rotating
_angle += _degreesPerSecond * Time.DeltaTime;
_radius += _radiusDelta * Time.DeltaTime;
Vector2 tmp;
tmp.X = -Mathf.Cos(_angle) * _radius;
tmp.Y = -Mathf.Sin(_angle) * _radius;
_velocity = tmp - position;
position = tmp;
}
else
{
Vector2 tmp, radial, tangential;
radial = Vector2.Zero;
if (position.X != 0 || position.Y != 0)
{
Vector2.Normalize(ref position, out radial);
}
tangential = radial;
radial = radial * _radialAcceleration;
var newy = tangential.X;
tangential.X = -tangential.Y;
tangential.Y = newy;
tangential = tangential * _tangentialAcceleration;
tmp = radial + tangential + emitterConfig.Gravity;
tmp = tmp * Time.DeltaTime;
_direction = _direction + tmp;
tmp = _direction * Time.DeltaTime;
_velocity = tmp / Time.DeltaTime;
position = position + tmp;
}
}
// update the particles color. we do the lerp from finish-to-start because timeToLive counts from particleLifespan to 0
var t = (_particleLifetime - _timeToLive) / _particleLifetime;
ColorExt.Lerp(ref _startColor, ref _finishColor, out color, t);
// update the particle size
particleSize += _particleSizeDelta * Time.DeltaTime;
particleSize = MathHelper.Max(0, particleSize);
// update the rotation of the particle
rotation += _rotationDelta * Time.DeltaTime;
if (collisionConfig.Enabled)
{
// if we already collided we have to handle the collision response
if (_collided)
{
// handle after collision movement. we need to track velocity for this
_velocity += collisionConfig.Gravity * Time.DeltaTime;
position += _velocity * Time.DeltaTime;
// if we move too slow we die
if (_velocity.LengthSquared() < collisionConfig.MinKillSpeedSquared)
{
return(true);
}
}
// should we use our spawnPosition as a reference or the parent Transforms position?
var pos = emitterConfig.SimulateInWorldSpace ? spawnPosition : rootPosition;
_circleCollisionShape.RecalculateBounds(particleSize * 0.5f * collisionConfig.RadiusScale,
pos + position);
var neighbors = Physics.BoxcastBroadphase(ref _circleCollisionShape.bounds,
collisionConfig.CollidesWithLayers);
foreach (var neighbor in neighbors)
{
CollisionResult result;
if (_circleCollisionShape.CollidesWithShape(neighbor.Shape, out result))
{
// handle the overlap
position -= result.MinimumTranslationVector;
CalculateCollisionResponseVelocity(collisionConfig.Friction, collisionConfig.Elasticity,
ref result.MinimumTranslationVector);
// handle collision config props
_timeToLive -= _timeToLive * collisionConfig.LifetimeLoss;
_collided = true;
}
}
}
}
else
{
// timeToLive expired. were done
return(true);
}
return(false);
}