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# Zerratar

Member Since 05 Sep 2013
Offline Last Active Jul 26 2015 02:05 PM

### #5242769How I tackled my performance issues developing an Android game in Unity

Posted by on 26 July 2015 - 09:43 AM

Hey guys!

I recently wrote an article on how I tackled my performance issues while i was developing my Android game Sky Blocks.
I was hoping that this article would help you guys to get some insight when developing for android or any other mobile devices using Unity.

I also want to see what you guys think about this article as well, critique and feedback are all welcome :-)

http://www.codeandux.com/tackling-performance-issues-in-unity-for-mobiles/

Best regards,
Karl / Zerratar

### #5091764Making a 3D model face the direction it's moving

Posted by on 05 September 2013 - 04:09 AM

Hi football94!

You can calculate the rotation between the two world points (Vector3)

This is what I used in my game:

```	public Quaternion GetRotation(Vector3 targetPos)
{
return GetRotation(this.Position, targetPos);
}

public Quaternion GetRotation(Vector3 entityPos, Vector3 targetPos)
{
// the new forward vector, so the avatar faces the target
Vector3 newForward = Vector3.Normalize(entityPos - targetPos);

// calc the rotation so the avatar faces the target
var src = Vector3.Forward;

var dest = newForward;

src.Normalize();
dest.Normalize();

float d = Vector3.Dot(src, dest);

if (d >= 1f)
{
return Quaternion.Identity;
}
if (d < (1e-6f - 1.0f))
{
Vector3 axis = Vector3.Cross(Vector3.UnitX, src);

if (axis.LengthSquared() == 0)
{
axis = Vector3.Cross(Vector3.UnitY, src);
}

axis.Normalize();
return Quaternion.CreateFromAxisAngle(axis, MathHelper.Pi);
}

float s = (float)Math.Sqrt((1 + d) * 2);
float invS = 1 / s;

Vector3 c = Vector3.Cross(src, dest);
Quaternion q = new Quaternion(invS * c, 0.5f * s);
q.Normalize();

return q;
}
```

when drawing your model use:

NewPosition = should be the target (future) position that your model is moving towards.

Quaternion RotationQuat = GetRotation(NewPosition);

then you need to store your RotationQuat and do NOT update it until your new "future" position is changed.

otherwise the model will rotate back the moment you stop moving.

for (int i = 0; i < bones.Length; i++)
{
bones[i] *=
Matrix.CreateFromQuaternion(RotationQuat)
* Matrix.CreateTranslation(position)
* Matrix.CreateWorld(Translation, Vector3.Forward, Vector3.Up); //Move the models position
...

I hope this helped

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