Cheat Engine

Dr.Disrespect · Posted: Sat Apr 02, 2016 5:44 pm Post subject: XMM registers, float, etc.

Please take a look at the attached pictures. When I open the FPU window and select "Float", the value of xmm0 is 75.00, but that value will change to "42960000" if I select "4 Bytes". What's the connection between "75" and "42960000"?

Moreover, after this:

Zanzer · Posted: Sat Apr 02, 2016 6:20 pm Post subject:

Yes, floats are stored in a floating point notation due to having so many more possibilities than whole numbers.
Their computed value is an approximation of the real number they represent.

42960000 is the hexadecimal representation of the bytes for 75.0.
00 00 96 42 is the same value as seen in an array of bytes instead.

The XMM registers are used for floats/doubles as well as converting to/from integers.

Dr.Disrespect · Posted: Sat Apr 02, 2016 6:35 pm Post subject:

Zanzer · Posted: Sat Apr 02, 2016 9:23 pm Post subject:

Yes, most games use floats for that because there are often modifiers, status bars, or various other reasons to use a decimal value.
Unless you're playing a turn-based game with grid movement, you're not likely to have whole numbers representing the unit's movement.

If you see XMM registers you can pretty much guarantee that you're going to be doing some decimal calculations.
Sometimes it may first load an integer to convert into a decimal and then do some math.
For example, armor may be represented by a 4-byte integer.
In order to reduce the damage taken, it may need to be converted into its decimal notation.

Or lets say you have a float health, like in most games.
Well you don't want to display it to the player as 99.9842389402384.
So you'll take the float value and convert it into an integer for display purposes.

Dr.Disrespect · Posted: Sat Apr 02, 2016 11:02 pm Post subject: