What does the Mean & Max mean in DeferredShadingCommon.usf?

I am reading the source code and found code like this:



// Octahedron Normal Vectors
// [Cigolle 2014, "A Survey of Efficient Representations for Independent Unit Vectors"]
//				Mean	    Max
// oct		8:8		0.33709 0.94424
// snorm	8:8:8		0.17015 0.38588
// oct		10:10		0.08380 0.23467
// snorm	10:10:10	0.04228 0.09598
// oct		12:12		0.02091 0.05874

float2 UnitVectorToOctahedron( float3 N )
{
	N.xy /= dot( 1, abs(N) );
	if( N.z <= 0 )
	{
		N.xy = ( 1 - abs(N.yx) ) * ( N.xy >= 0 ? float2(1,1) : float2(-1,-1) );
	}
	return N.xy;
}



Wanna know what those values mean……

This is mean and maximum deviation of an uncompressed vector from a vector, that was compressed and decompressed, measured in degrees.