Don’t you just love getting email from your friends. I am sure that as you read this you may think about past jokes and humerous anecdotes received.

I don’t get many like that, this is what I got from a friend of mine today,

How bout this for a fast invsqrt…

float InvSqrt(float x)

{

float xhalf = 0.5f * x;

int i = *(int *)&x;

i = 0x5f3759df – (i >> 1);

x = *(float *)&i;

x = x * (1.5f – xhalf * x * x);

return x;

}

Explanation given here (not for the faint of heartr)

http://www.math.purdue.edu/~clomont/Math/Papers/2003/InvSqrt.pdf

You have to see the explanation and Steve’s right its not for the faint of heart.

So any XNA peeps who stumble along here might you be interested.

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For a better explanation about this, check out http://www.mceniry.net/papers/Fast%20Inverse%20Square%20Root.pdf