Tube Shooter Movement Design Help

Questions & Answers
1

So I’m making a 2D “Tube Shooter”. If you’re not sure what that is look up Gyruss. I’m having a bit of a problem with my implementation of the circular pattern of movement.

I’ve decided to implement the movement using a combination of rotation and translation functions. This makes the ship appear like it is moving in a circular pattern while keeping the front of the ship pointed to the center. I feel like I may be taking the hard road here in implementation of this feature of the game. Here is my code for control.

using UnityEngine;
using System.Collections;

public class PlayerControl : ShipClass
{	
	public Transform shotStart;
	public PlayerShot shot;

	void FixedUpdate () 
	{

        //Movement Control
		int xAxisValue = (int) Input.GetAxis ("Horizontal");
		int yAxisValue = (int) Input.GetAxis ("Vertical");
		switch(xAxisValue)
		{
		case 1:
            transform.Rotate (0, 0, p_rotateSpeed);
			transform.Translate (1 * p_Speed * Time.deltaTime, 0, 0);
            break;
		case -1:
            transform.Translate (-1 * p_Speed * Time.deltaTime, 0, 0);
            transform.Rotate (0, 0, -p_rotateSpeed);
			break;

		default:
			break;
		}

        //Y axis isn't implemented currently as I'm just testing out moving left and right.
		switch(yAxisValue)
		{
		case 1:
			transform.Translate (0, -1 * p_Speed * Time.deltaTime, 0);
			break;

		case -1:
			transform.Translate (0, 1 * p_Speed * Time.deltaTime, 0);
			break;

		default:
			break;
		}


        //Firing mechanism
        /*
		if (Input.GetButtonDown ("Fire2")) 
		{
			Debug.Log ("Fire2 pressed!");
			Instantiate(shot, shotStart.position, shotStart.rotation);
		}
        /*

		
		/*
		 * 
		 * Debug Purposes
		 * 
		 * 
		if(Input.GetKey("a"))
			transform.Translate (-1 * player.p_Speed * Time.deltaTime, 0, 0);
		if (Input.GetKey ("d"))
			transform.Translate (1 * player.p_Speed * Time.deltaTime, 0, 0);
		if (Input.GetKey ("s"))
			transform.Translate (0, -1 * player.p_Speed * Time.deltaTime, 0);
		if (Input.GetKey ("w"))
			transform.Translate (0, 1 * player.p_Speed * Time.deltaTime, 0);

		Debug.Log (Input.GetAxis ("Vertical"));
		*/
	}
}

My problem comes from the way the ship moves. It doesn’t move in a perfect circle. More specifically when the ship moves from its starting position to the top of the screen it has shifted slightly on the X axis when I want it to end up in the same position just a direct inverse of the Y starting position.

Here are my questions. Is there a better way to implement this? If not is there something I’m missing that makes the ship act like this?

2

You should check into Transform.RotateAround(). If you have the camera with rotation (0,0,0) and position (0,0,x), getting Gyruss type functionality is as simple as:

using UnityEngine;
using System.Collections;

public class Control : MonoBehaviour {

	public float rotateSpeed = 8.0f;

	void FixedUpdate() {
		transform.RotateAround(Vector3.zero, Vector3.forward, rotateSpeed * Input.GetAxis ("Horizontal"));
	}
}

You could also do the rotation in Update() instead of FixedUpdate() and scale the rotation by Time.deltaTime.