Bullet Pattern for Bullet Hell

Questions & Answers
1

Hi all, I’m designing a bullet hell game and already came up with some patterns.
However, I’m stuck now trying to achieve a certain pattern.
I’m trying to make the bullet stream accelerate into a spiral clockwise then slow down and spin counter clockwise. I manage to make it spiral clockwise but couldn’t get it to change direction. Please help. Thanks.

public IEnumerator Pattern006()
    {
        yield return new WaitForSeconds(nextShot);

        GameObject enemyShot = enemyShots[mainShot];
        float stepAngle = 360.0f - (360.0f / numberOfSpirals);

        if (nextShot <= countdown)
        {
            acceleration += rotationSpeed;

            for (int i = 0; i <= numberOfSpirals - 1; i++)
            {      
                float shotDirX = shotSpawnPoint.position.x + Mathf.Sin(((angle + stepAngle * i) * Mathf.PI) / 180f);
                float shotDirY = shotSpawnPoint.position.y + Mathf.Cos(((angle + stepAngle * i) * Mathf.PI) / 180f);

                Vector3 shotMoveVector = new Vector3(shotDirX, shotDirY, 0f);
                Vector3 shotDir = (shotMoveVector - shotSpawnPoint.position).normalized * shotSpeed;

                GameObject shot = Instantiate(
                    enemyShot, 
                    shotSpawnPoint.position, 
                    Quaternion.Euler(0.0f, 0.0f, -(angle + stepAngle * i))
                );
                shot.GetComponent<Rigidbody>().velocity = new Vector3(shotDir.x, shotDir.y, 0.0f);
            } 

            angle += acceleration * Time.deltaTime;

            if (acceleration >= 1000.0f)
                acceleration = 1000.0f;

            countdown = 0.0f;
        }
    }
2

It’s ok everyone, woke up with the formula in my head.
Here’s the solution I came up with

public IEnumerator Pattern006()
    {
        yield return new WaitForSeconds(nextShot);

        GameObject enemyShot = enemyShots[mainShot];
        float stepAngle = 360.0f - (360.0f / numberOfSpirals);

        if (nextShot <= countdown)
        {
            acceleration += rotationSpeed / 50.0f;

            for (int i = 0; i <= numberOfSpirals - 1; i++)
            {      
                float shotDirX = shotSpawnPoint.position.x + Mathf.Sin(((angle + stepAngle * i) * Mathf.PI) / 180f);
                float shotDirY = shotSpawnPoint.position.y + Mathf.Cos(((angle + stepAngle * i) * Mathf.PI) / 180f);

                Vector3 shotMoveVector = new Vector3(shotDirX, shotDirY, 0f);
                Vector3 shotDir = (shotMoveVector - shotSpawnPoint.position).normalized * shotSpeed;

                GameObject shot = Instantiate(
                    enemyShot, 
                    shotSpawnPoint.position, 
                    Quaternion.Euler(0.0f, 0.0f, -(angle + stepAngle * i))
                );
                shot.GetComponent<Rigidbody>().velocity = new Vector3(shotDir.x, shotDir.y, 0.0f);
            } 

            angle = Mathf.Sin(acceleration) * 360.0f * spinDuration;

            countdown = 0.0f;
        }
    }

The amount that the rotationSpeed is divided by requires some tweaking to achieve the desired rotational speed. Hope this helps anyone who is stuck with the same problem.