Particle as projectile (parabola movement with gravity modifier)

Questions & Answers
1

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I am making the arrow rain effect by using particle system (emit angle 60 degree + gravity modifier + start speed), is it possible to calculate the “start speed” by the given start position and end position so that the arrows can emitted to the target area ?

I tried script as below but the projectile velocity is not same as the “start speed”.

var gravity = 9.8f; var firingAngle =
60f; float target_Distance =
Vector3.Distance(transform.position,
target); float projectile_Velocity =
target_Distance / (Mathf.Sin(2 *
firingAngle * Mathf.Deg2Rad) /
gravity);

2

Answer to myself

Particle settings :
 Gravity modifier = 1
 Shape - rotation x, y, z = -60 , 0 , 0
 
 Trajectory prediction by finding the startSpeed :
 particle gameObject :
 transform.position = startposition;
 var distance = Vector3.Distance(targetposition, startposition);
 var v = Mathf.Sqrt(distance / (Mathf.Sin(2 * 60 * Mathf.Deg2Rad) / 9.8f));
 var main = fireParticles.main;
 main.startSpeed = v;