Question

I noticed a very strange thing in my application. There are two static const integers in my World class:

class World
{
  public:
    static const int CHUNK_SIZE_X = 32;
  private:
    static const int SHIFT_X;
};

The constant SHIFT_X is initialised in the corresponding *.cpp file:

const int World::SHIFT_X = Ogre::Math::Log2(World::CHUNK_SIZE_X);

Now the strange thing is that the value in SHIFT_X is 4 instead of 5. If I call Ogre::Math::Log2(32) from within an arbitrary method it correctly computes 5.

What the hell is going on here? I also need to say that this only happens under Windows 7 (with Visual Studio Express 10). My application also runs under GNU/Linux (Debian Squeeze) and there everything works fine.

Answer 1

Ogre::Math::Log2 returns a Real which is actually a float and you are trying to store it as an int. Therefore if the value returned was 4.9999999999999998 it would still end up with 4 after the conversion. If you would like to continue using an int instead of a float you should round the value.