FloatUnion.approxSqrt By Frank Savage (Development Manager – XNA Tools Team)

I was listening to the GDC09 talks and Mr Savage did his performance talk he mentioned a FloatUnion struct for approximate square root, but I could never find it until now…

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using System.Runtime.InteropServices;
 
[StructLayout(LayoutKind.Explicit)]
public struct FloatUnion
{
	[FieldOffset(0)]
	public float x;
 
	[FieldOffset(0)]
	public int n;
 
	public float approxSqrt()
	{
		n -= 1 << 23;
		n = n >> 1;
		n += 1 << 29;
		return x;
	}
}

This was more for me, but it’s here if you ever need it :-)

2009
05/20
POSTED BY
Dave
CATEGORY
Game Development
TAGS

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