3 ms·
I never use the square root in games, I always compare squared distances (since the properties are the same). If you try to do with Fixed Point Arithmetic what
by linkdd 6y ago
I never use the square root in games, I always compare squared distances (since the properties are the same).
If you try to do with Fixed Point Arithmetic what was intended to be done with Floating Point, you're the problem.
A 32 bits integer can hold values up to 4 billions, if I have that kind of value in a simple game, then yes i will switch to Floating Point Arithmetic, but when does that use case happen if you're not writing a physic simulation game ?
- adwn 6y agoIt appears you have a very niche definition of "game", one which excludes basically all 3D games.
- linkdd 6y agoYes, that's exactly why I wrote: > some game engines and > simple games A 3D game is not a simple game.
- adwn 6y agoUgh, do you really have to be this nitpicky? Fine, you wrote: > the approximation is generally good enough for a game No, it's not generally good enough for a game – only for some games, and not good enough for any game with 3D graphics.
- Qwertious 6y agoSpeaking of nitpicky, I thought the gamecube's GPU was integer-driven? And it has plenty of 3D games.
- yvt 6y agoTechnically, 32-bit fixed-point numbers have 8-bit more precision compared to 32-bit floating-point numbers, but the real problem is it's quite cumbersome to fully utilize the precision offered by fixed-point numbers as you'd have to keep in mind their numerical range all the time.
- quelsolaar 6y ago> A 32 bits integer can hold values up to 4 billions, if I have that kind of value in a simple game, then yes i will switch to Floating Point Arithmetic, but when does that use case happen if you're not writing a physic simulation game ? All the time. Let me give you an example from a game I made. During early R&D I used 32 bit numbers and a fixed point of 11 bits. That means that a normalized vector is between 1024 and -1023. You can do 2 dot products between vectors before it breaks it breaks. (10 + 10 + 10 bits plus one sign bit). That means that you have to do a lot of shifting down. the world can only be 20 bits large, because you need to be able to multiply world coordinates with vectors without getting overflow. 20 bis is very low resolution for a real-time world. You get problems with things not being able to move slow enough at high frame rates. (this was in 2D). Switching to 64 bit was the right move.
- edflsafoiewq 6y agoThe biggest problem with fixed point is reciprocals behave very poorly; ie. x·(1/x)=1 and 1/(1/x)=x fail very badly. In order for these to work you obviously need the same amount of numbers above 1 as below 1, like in floating point. Using fixed point with 11 bits after the decimal, with numbers as low as 100 (18 bits) we already have errors as large as 100·(1/100)=0.977.