Let''s say I have the x and y componets of a vector, and I want to change its total Magnitude to 8(or any other number) while maintaing its current direction. How would I go about doing this? Thanks.

  Magnitude = sqrt( (x*x) + (y*y) );Direction = atan2(y, x);  

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float myVec[ 3 ], mag;

mag = sqrt( myVec[ 0 ]*myVec[ 0 ] + myVec[ 1 ]*myVec[ 1 ] + myVec[ 2 ]*myVec[ 2 ] );

myVec[ 0 ] *= ( 8.0f / mag );
myVec[ 1 ] *= ( 8.0f / mag );
myVec[ 2 ] *= ( 8.0f / mag );

Normalising a vector reduces its magnitude to 1, so you can then multiply by 8 to get what you want. This gives the result that the AP showed. But that can be optimised:

ScaleFactor = 8.0f / sqrt(myVec[0]*myVec[0] + myVec[1]*myVec[1] + myVec[2]*myVec[2]);

myVec[0] *= ScaleFactor;
myVec[1] *= ScaleFactor;
myVec[2] *= ScaleFactor;