public override HardwarePixelBuffer GetBuffer( int face, int mipmap )
{
if ( face >= this.faceCount )
throw new IndexOutOfRangeException( "Face index out of range" );
if ( mipmap > MipmapCount )
throw new IndexOutOfRangeException( "MipMap index out of range" );
int idx = face * ( MipmapCount + 1 ) + mipmap;
Debug.Assert( idx < _surfaceList.Count );
return _surfaceList[ idx ];
}