Unity Android compression – ETC2 vs. ETC1

I’ve been working on a Unity project for Android and iOS lately. For Android we had been using ETC2 for the texture  compression. The ETC2 benefits were:

  • Better performance on devices where it’s supported.
  • Supports non power of 2 textures.
  • Works with all Unity UI canvas types.

The UI canvas support was particularly important to us as the project uses Unity UI extensively and almost entirely built with it.

Unfortunately it turned out that there are still quite a few modern, popular, low end devices that don’t support ETC2 (it’s supported on OpenGL ES 3.0 devices), like the Samsung J1.

When a device doesn’t support ETC2 the textures are uncompressed and because they are low end or old devices it increases the likelyhood that they will run out of memory when you load alot of assets in a scene. Not a good scenario.

Realistically this makes ETC1 the better choice for now as it’s supported by all devices. However ETC1 does come with its own pitfalls:

  • Doesn’t work with Unity UI Overlay Canvas types
  • Can’t be loaded from Resources with Alpha intact
  • Requires a packing tag to support alpha channel
  • Renders alpha channel seperately making packed sheets hard to preview.
  • Performance is not as good as ETC2, but this won’t matter as much for devices that support ETC2 as they should be capable of handling it since they are better devices.

Creating a grid of objects

Here’s some stripped down code I use to create a grid of objects in Unity. I’ve used this setup in my Android game Block Blaze when the level is initialised. It’s attached to a Generator object, which also has some other functionality like determining what type of object is created, whether an object needs to be regenerated if its destroyed, what object types are neighbouring, etc.,

public GameObject sampleObj;
public GameObject[,] array = new GameObject[5,4];

private int columns = 4,rows = 5;
private float Xpos = 2.0f;
private float Xoffset = 2.0f;
private float Ypos = 1.0f;
private float Yoffset = 2.0f;

void Start ()
{
for (int j = 0; j < rows; ++j)
{
for (int i = 0; i < columns; ++i)
{
if(array[j,i] == null)
{
sampleObj.name = j + " " + i;
array[j,i] = (GameObject) Instantiate (sampleObj, new Vector3(Xpos * (Xoffset * i),Ypos * (Yoffset * i),0), Quaternion.identity);
}
}
}
}

Unity3D Development – Rigidbody Reset Force / Motion Code

In my new game I need to be able to give an object in motion a new force (same magnitude) in a random direction with a button press. Here’s my C# solution using Coroutines.
Its working perfectly for me and solves the weird physics problem with stopping/starting using rigidbody.isKinematic.

All these code snippets are in the script attached to the object:

Vector3 eulers = Vector3.zero;
private bool waiter;

IEnumerator shotRedirect()
{
yield return new WaitForSeconds(0.0f);
eulers = transform.eulerAngles;
eulers.x = Random.Range(0,360);
transform.eulerAngles = eulers;
rigidbody.isKinematic = true;
StartCoroutine(shotRedirectPart2());
}

IEnumerator shotRedirectPart2()
{
yield return new WaitForSeconds(0.01f);
rigidbody.isKinematic = false;
rigidbody.AddForce(transform.forward * shotPower);
}

private void Waits()
{
waiter = true;
}

void Update()
{
if(waiter == true)
{
if (Input.GetKeyDown(KeyCode.A))
{
StartCoroutine(shotRedirect());
}
waiter = false;
Invoke("Waits",0f);
}
]