public ParticleGroup CreateGroup(string name = null)
{
var pGroup = new ParticleGroup(this);
pGroup.Name = name;
pGroup.Particles.Capacity = this.ParticleCount;
return(pGroup);
}
public void DrawGroup(SpriteBatch sprite, ParticleGroup pGroup, Vector2 position)
{
if (this.Texture?.Texture == null)
{
return;
}
var textureSize = this.Texture.AtlasRect?.Size.ToVector2() ?? new Vector2(this.Texture.Texture.Width, this.Texture.Texture.Height);
var rad = textureSize.Length() / (float)Math.Sqrt(2);
var origin = this.Texture.Origin.ToVector2();
position += pGroup.Position;
foreach (var p in pGroup.Particles)
{
var color = Lerp(p.StartColor, p.EndColor, p.NormalizedTime);
var size = MathHelper.Lerp(p.StartSize, p.EndSize, p.NormalizedTime);
var scale = size / rad;
var rot = MathHelper.ToRadians(MathHelper.Lerp(p.StartSpin, p.EndSpin, p.NormalizedTime));
//重新计算alpha
if (this.alphaPoints.Length > 0)
{
color.A = (byte)CalcAlphaFromPoints(p);
}
if (this.OpacityModifyRGB)
{
if (color.R == 0 && color.G == 0 && color.B == 0)
{
color.R = color.G = color.B = color.A;
}
else
{
//float alpha = color.A / 255.0f; ;
//color.R = (byte)(color.R * alpha);
//color.G = (byte)(color.G * alpha);
//color.B = (byte)(color.B * alpha);
}
}
var pos = p.Pos + position;
sprite.Draw(this.Texture.Texture, pos, this.Texture.AtlasRect, color, rot, origin, scale, SpriteEffects.None, 0);
}
}
public void UpdateGroup(ParticleGroup pGroup, TimeSpan elapsed)
{
var time = (float)elapsed.TotalSeconds;
if (pGroup.IsActive)
{
if (pGroup.Particles.Count < this.ParticleCount) //生成粒子
{
float emitCount = this.Emitter.EmissionRate * time;
var count = (int)emitCount + (this.Rand.NextPercent(emitCount % 1) ? 1 : 0);
count = Math.Min(count, this.ParticleCount - pGroup.Particles.Count);
for (int i = 0; i < count; i++)
{
var p = this.Emitter.Emit();
if (p.Life <= 0) //fix bug
{
continue;
}
pGroup.Particles.Add(p);
}
}
//计算时间
if (this.Duration > 0)
{
pGroup.Time += time;
if (pGroup.Time > this.Duration)
{
pGroup.IsActive = false;
}
}
}
//更新所有粒子
if (pGroup.Particles.Count > 0)
{
pGroup.Particles.ForEach(p =>
{
p.Time += time;
p.NormalizedTime = p.Life <= 0 ? 0 : (p.Time / p.Life);
if (p.NormalizedTime >= 1)
{
return;
}
//更新粒子
var accDir = p.Pos;
if (accDir != Vector2.Zero) //计算方向
{
accDir.Normalize();
}
var radial = accDir * p.RadialAcc; //法线加速度矢量
//var tangent = new Vector2(-accDir.Y, accDir.X) * p.TangentialAcc; //切线加速度矢量
var tangent = Vector2.Zero; //tangent not works in the game?
var acc = this.Gravity + radial + tangent; //总加速度矢量
p.Dir += acc * time; //计算加速度
p.Pos += p.Dir * time; //计算位置
//计算旋转
p.Angle += p.RotatePerSecond * time;
var rad = MathHelper.Lerp(p.StartRadius, p.EndRadius, p.NormalizedTime);
if (rad > 0)
{
var radian = MathHelper.ToRadians(p.Angle);
accDir = new Vector2((float)Math.Cos(radian), (float)Math.Sin(radian));
p.Pos += accDir * rad * time;
}
});
//回收粒子
pGroup.Particles.RemoveAll(p =>
{
if (p.NormalizedTime >= 1)
{
this.CollectParticle(p);
return(true);
}
else
{
return(false);
}
});
}
}
