float dRad(Particle p)
{
var l = p.Lifetime / p.MaxLifetime;
var initRate = InitRadius / 25;
return initRate * (1 + l) * (1 - l);
}
void init(Vector2 cent, float blastRad, int numParts, float maxLife, float initRad, float pmass, float maxangspd)
{
_cent = cent;
Particles = new List<Particle>();
InitRadius = initRad;
for (int i = 0; i < numParts; i++)
{
var life = maxLife / 2 + (float)MathUtils.Rand.NextDouble() * maxLife / 2;
var p = new Particle(InitRadius, pmass, life);
p.Position = cent + (float)MathUtils.Rand.NextDouble() * blastRad * MathUtils.RandDirection();
p.Rotation = (float)(MathUtils.Rand.NextDouble() * 2 * Math.PI);
p.AngularVelocity = (float)(2 * maxangspd * MathUtils.Rand.NextDouble() - maxangspd);
Particles.Add(p);
}
}
float alpha(Particle p)
{
var l = p.Lifetime / p.MaxLifetime;
var a = 4*l * (1 - l);
if (a < 0) a = 0;
if (a > 1) a = 1;
return a;
}