Learn how your comment data is processed. public static float Floor (float f); Description. exp, sin, etc.). Switch to Manual. We solved it by clustering the game world into independent clusters of objects (minimal cluster size is 20km). Since code should include sufficient casts to ensure that a code reviewer would have no reason to doubt that the programmer meant what he wrote, I would suggest that language designers should base their type-conversion rules on that principle. How is it possible then that the max value of int is 2 31, and the max value of float is 3.4*10 38, while both of them are 32 bits? Memory size for each data type is different. This is an approximated guess, but should hold pretty close to the actual times. Which is poor odds. When you work with entire arrays of something, packing can help a lot. The double data type is more precise than float in Java. Float and Double both are the data types under Floating-point type. I’m not sure that a default float type of double helps — after all, the default float type in C/C++ is also double, but for performance reasons many people explicitly choose float. The range of double is 5.0 × 10 −345 to 1.7 × 10 308. http://blog.marekrosa.org/2014/12/space-engineers-super-large-worlds_17.html. Thank you! News, Help, Resources, and Conversation. Unfortunately, many languages like Java and C# fall flat. Space Engineers and KSP use floats and dynamic frames of reference because Havok and Unity respectively don't (or in KSPs case, didn't) support 64-bit physics. Switch to Manual. Number of Bytes: The float is 4 bytes long. Circular orbits were my first step (in learning C# and the unity environment) - now I'm wanting to expand it - and my design really requires me to be able to "swing" around planets :). As you say at the end, the solution is to match constants and variables; either use 1.1f or use a double. We can create a variable to store a change in size. But flexibility comes at the cost of a LOT of work: with surface shaders, Unity takes care of all (almost) the PBR lighting and shadowing so you just have to worry about the shader itself. Excellent discussion. I’ve seen a few online discussions linking to my Comparing Floating Point Numbers page for misguided reasons and I wanted to discuss those reasons to help people understand why throwing epsilons at the problem without understanding the situation is a Really Bad Idea™. int can hold only integer numbers, whereas float also supports floating point numbers (as the type names suggest). Float vs. Very clear and point to point reply. The advantages of single-precision floats just aren’t enough. Returns f rounded to the nearest integer. The worst counter-example to the superstition “testing floats with equality is always bad” may be this one, where the tested value is an infinite: http://stackoverflow.com/questions/11421756/weverything-yielding-comparing-floating-point-with-or-is-unsafe, A couple more examples are in this post of mine (it can get tricky, but that does not undermine the message that floating-point is deterministic): http://blog.frama-c.com/index.php?post/2011/11/08/Floating-point-quiz. Floating point is subtle, but it’s not inherently nondeterministic. Precision is the main difference where float is a single precision (32 bit) floating point data type, double is a double precision (64 bit) floating point data type and decimal is a 128-bit floating point data type. The other example I’ve seen where people are too quick to pull out an epsilon value is comparing a constant to itself. Hm. Until now, Space Engineers and its physics engine (Havok) were using single-precision 32-bit floating point numbers. float means that sizeModifierstores a floatin… Or better still, switch to a language like Pike, where the default float type is double precision, AND you get an arbitrary-precision float type (Gmp.mpf, using the GNU Multiprecision Library). Pingback: Float Precision Revisited: Nine Digit Float Portability | Random ASCII, Pingback: Comparing Floating Point Numbers, 2012 Edition | Random ASCII. Add Component > New Script Name: Floater; Language: C-Sharp; Edit the script; Copy & Paste the code below into your script editor. Here's a few of the basic types: Anyway, thanks for your help and the resource. The examples are extremely valuable when one’s thinking isn’t as clear as it should be. For example, the following declarations declare variables of the same type:The default value of each floating-point type is zero, 0. Float and double are similar types. The main barrier to Unity using doubles to track positions would be that doing so would mean a performance decrease for all projects using Unity, regardless if they need the changes or not, and 99% (possibly higher) of games don't actually need worlds in excess of what can be achieved with the current floating point limitations (I.E. But first let’s practice base conversion. Well, I’ve written a script for that. Each of the two sets of curly brackets represents the minutes and seconds values of the time display. How did we increase the precision of numerical computations? Sure, it works (and if someone’s using 42 to initialize a double, rather than 42.0, that’s not a problem, since small integers are perfectly representable in floats), but it’s setting you up for confusion later. In C#, the naming convention for variables is to capitalize the first letter of every word after the first word. Alternatively, I can work this using the design of the game rather than physics. The confusion, presumably, comes from the fact that 1.1 looks like such a simple number, and therefore the naive expectation is that it can trivially be stored in a float. The Floating-point numbers are the real numbers that have a fractional component in it. Ever wanted to make an object float up and down while spinning in Unity? Floats suck!\n”); double x = 1.1;if (x != 1.1)    printf(“OMG! Press J to jump to the feed. And if you do SSE SIMD coding then you can process floats twice as fast as doubles. Cookies help us deliver our Services. Two reasonable ways to fix the initial code would be: float x = 1.1f; // Float constantif (x != 1.1f) // Float constant    printf(“OMG! Floats definitely still have significant advantages. Here are some numbers to think about: an AU is ~ 1.5*1014 millimeters. They had to work around with even 6.6AU. A User Showcase of the Unity Game Engine. As a result Havok doesn’t need to use double-precision math (physics calculations are faster in single-precision mode). I just changed it to make them consistent in order to avoid any possible confusion. Float uses 1 bit for sign, 8 bits for exponent and 23 bits for mantissa but double uses 1 bit for sign, 11 bits for exponent and 52 bits for the … In programming, it is required to store data. Update: this guarantee is mostly straightforward (if you haven’t recompiled then you’ll get the same results) but nailing it down precisely is tricky. Having the precision of your floating-point numbers depend on the size of your address space seems bizarre. We have modified all game objects to support double-precision 64-bit floating point numbers -- this was the easy part The harder one was to change the integration between Space Engineers and Havok (so Havok can keep using 32-bit floating point numbers). A physics engine is overkill and will impose limitations on what you will be able to do. The difference between the two is in the size of the numbers that they can hold. An arbitrary precision float type is a great thing to have, but used carelessly it just gives you the same issues only with smaller epsilons. In one of the examples, why do you use float(1.1) and (double)1.1, and thus not double(1.1)? The net result is that the binary representations of 1.1 in float (24-bit mantissa) and double (53-bit mantissa) precision are: double(1.1) = %1.0001100110011001100110011001100110011001100110011010. All of the integers from 0 to 2^24 (about 16 million) are representable in a float, and many more are representable in a double, and most of them don’t end in 5. I think the real problem is with the over-simplistic design of operator overloading and promotion. Make your own math library with arbitrary precision, unless you're going to run thousands of small asteroids and stuff, and mostly focus on planets/moons, just make some 256bit fixed point number system by hand, something like Q128.128 should give you more precision than you need (i think). I think that most new developers assume that using 1.1 as a float constant is as benign as using 42 as a float constant. _UF -> UNITY_FLOAT _UD -> UNITY_DOUBLE _UU -> UNITY_UINT _UU32 -> UNITY_UINT32 _US16 -> UNITY_INT16. You can then compare that to another literal, no problem. For example, 2/10, which is represented precisely by .2 as a decimal fraction, is represented by .0011111001001100 as a binary fraction, with the pattern "1100" repeating to infinity. Change ), You are commenting using your Twitter account. I don't think JSON distinguishes 4-byte vs. 8-byte floating point types does it? You can take advantage of this to create some nifty smooth transition functions. Suppose we want to change the size of the cube we created last time. Tom Forsyth likes to point out that sometimes switching to double just means your bugs now only occur after hours of playtime, or in distant corners of the map. Rather than having a broad rule “float-to-double is allowed implicitly; double-to-float isn’t” it would be more helpful to allow more case-by-case determinations. The slight breaking of the pattern at the end of both numbers is because the conversion is done with round-to-nearest rather than truncation, in order to minimize the error in the approximation, and in both cases it is rounded up. What I'm looking to do is create a strategy game (well, that's a ways down the line) that incorporates orbital mechanics - i.e, a sort of KSP RTS, however, I suppose that the mass and size of the ships does not need to be represented realistically. The first thing we're gonna do is create a new “Standard Surface Shader”.Some people may prefer a fixed-function shader for this particular case, as those are more flexible. This data format has a certain precision, leading to visible imperfections on objects located further than 10km from the origin. Realistically, you won't notice a planet wiggling by a few hundred meters, let alone a few cm, out to a much larger distance. In fact, if you take a randomly selected double then the odds of it being perfectly representable in a float are about one part in 4 billion. Understanding these guarantees is important. Float - 32 bit (7 digits) I wouldn’t want to speak so definitely about what most people work with most of the time, but just be aware that doubles don’t actually solve all of the problems of binary floating-point math. As a programmer who used to avoid floats and doubles whenever possible (because I didn’t understand the “magic” behind them) and is getting to C/C++ game programming, this post and all the others about the subject taught me I was doing it wrong. I think the real problem is with the over-simplistic design of operator overloading and promotion. If you are dealing with large arrays of them then the memory savings (and reduced cache misses) can be critical. And no angels harmed. A double loses precision as the value it is approximating increases, of course, but an IEEE 754 64-bit double will still be within 1 of any number less than, say, 2^53, or 9*1015. Once he realized that floating-point instability was not the problem he quickly found that his code had some race conditions, and those had been the problem all along. We have modified all game objects to support double-precision 64-bit floating point numbers -- this was the easy part The harder one was to change the integration between Space Engineers and Havok (so Havok can keep using 32-bit floating point numbers). Unity is the ultimate game development platform. There seems to be a belief that if you redo the exact same calculation with the exact same inputs then you might get a different answer. Don’t expect the result of double-precision calculations to equal the result of float-precision calculations, even when the only ‘calculation’ is converting from decimal to binary floating point. In some cases, comparing floating-point numbers for exact equality is actually correct. If not, the difference might be much smaller, but it is very dependent on your CPU. So the guarantee is really that the same machine code will produce the same results, as long as you don’t do something wacky. I can probably tackle this next week if you need me to. The leading ‘1’ converts straight across, and to generate subsequent binary digits we just repeatedly multiply by two. Thank you so much. I’m not sure about the compilation defaults; if the default for a 32-bit build really is a 32-bit float, it’s probably just because nobody’s wanted to go in and change it, just in case it breaks stuff. More generally, I’d allow parameters to functions to indicate whether they should allow or disallow explicit casts, since there are situations where double-to-float should be accepted silently (e.g. However if you start adding epsilons carelessly – if you allow for error where there should be none – then you get a chaotic explosion of uncertainty where you can’t tell truth from fiction. Cancel. Default Values: The default value of float is 0.0f. As you probably know, both of these types are 32-bits. Nice — I appreciate the comment and the links. If you have a well-trimmed pipeline using SIMD, you will be able to do twice the number of FLOPS with float vs double. One quibble: in the Floating-point-quiz you say “For a decimal number to be representable as a (base 2) floating-point number, its decimal expansion has to end in 5” but that is only true if there is a fractional part. Memory locations that store data are called variables. 100% applies to the newest line of NVidia cards and 300% applies to their 100 series. I could feasibly do what I'm trying to accomplish in two ways: The first would be to go ahead and split the space up into clusters, maintaining the vector and distance towards the sun for each object (I'm operating in 2D, not worrying about 3D yet, which makes coding "real" physics actually pretty easy). Float is a single-precision, 32-bit floating point data type; double is a double-precision, 64-bit floating point data type. Life will be better. The easiest is just: rocketBoostPower = Mathf.Lerp(rocketBoostPower , tempForce,t); Generally if you want mathematical precision, you would not use a game engine to do it. But if you stick to the basic five operations (plus, minus, divide, multiply, square root) and you haven’t recompiled your code then you should absolutely expect the same results. I would guess that that is because the ‘int’ type is the size of a pointer so ‘float’ might as well be also, but still. An awesome reminder of how to do base conversion and why we had to learn it in the first place! If you want begin representing AU roughly accurately you're going to need a bit more than doubles, From Marek Rosa's Blog on Space Engineers (6.6AU infinite worlds](http://blog.marekrosa.org/2014/12/space-engineers-super-large-worlds_17.html). Here is a typical example of the code that triggers this: float x = 1.1;if (x != 1.1)    printf(“OMG! Here's a talk where KSP devs discuss it. And GPUs still process floats a lot faster than doubles. ( Log Out /  Close. Floating-point as the scapegoat delayed his finding of the real bug by almost a month. There are caveats: the way some SSE instructions are specified is a bit of a minefield, and we’re trying to figure out now how we can make things work reliably across architectures, but the main point is valid. if (x == 0.5) Fill in your details below or click an icon to log in: You are commenting using your WordPress.com account. I'm seeing a lot of incorrect information on this thread. ( Log Out /  Floats suck!\n”); On a fairly regular basis somebody will write code like this and then be shocked that the message is printed. If you do a series of operations with floating-point numbers then, since they have finite precision, it is normal and expected that some error will creep in.