class in UnityEngine
Thank you for helping us improve the quality of Unity Documentation. Although we cannot accept all submissions, we do read each suggested change from our users and will make updates where applicable.Close
For some reason your suggested change could not be submitted. Please <a>try again</a> in a few minutes. And thank you for taking the time to help us improve the quality of Unity Documentation.Close
Easily generate random data for games.
This static class provides several easy game-oriented ways of generating pseudorandom numbers.
The generator is an Xorshift 128 algorithm, based on the paper Xorshift RNGs by George Marsaglia. It is statically initialized with a high-entropy seed from the operating system, and stored in native memory where it will survive domain reloads. This means that the generator is seeded exactly once on process start, and after that is left entirely under script control.
For more details on the seed, including how to manage it yourself, see InitState. To learn how to save and restore the state of Random, see state.
This class has the same name as the .NET Framework class System.Random and serves a similar purpose, but differs in some key ways:
Static vs instanced
UnityEngine.Random is a static class, and so its state is globally shared. Getting random numbers is easy, because there is no need to
new an instance and manage its storage. However, static state is problematic when working with threads or jobs (the generator will error if used outside the main thread), or if multiple independent random number generators are required. In those cases, managing instances of
System.Random would be a better option.
Float upper bounds are inclusive
All properties and methods in
UnityEngine.Random that work with or derive work from float-based randomness (for example value or ColorHSV) will use an inclusive upper bound. This means that it is possible, though as rare as any other given value, for the max to be randomly returned. In contrast,
System.Random.NextDouble() has an exclusive maximum, and will never return the maximum value, but only a number slightly below it.
UnityEngine.Random have been measured to be between 20% and 40% faster than their equivalents in
Name resolution ambiguity
Because the classes share the name
Random, it can be easy to get a CS0104 "ambiguous reference" compiler error if the
UnityEngine namespaces are both brought in via
using. To disambiguate, either use an alias
using Random = UnityEngine.Random;, fully-qualify the typename e.g.
UnityEngine.Random.InitState(123);, or eliminate the
using System and fully-qualify or alias types from that namespace instead.
|insideUnitCircle||Returns a random point inside or on a circle with radius 1.0 (Read Only).|
|insideUnitSphere||Returns a random point inside or on a sphere with radius 1.0 (Read Only).|
|onUnitSphere||Returns a random point on the surface of a sphere with radius 1.0 (Read Only).|
|rotation||Returns a random rotation (Read Only).|
|rotationUniform||Returns a random rotation with uniform distribution (Read Only).|
|state||Gets or sets the full internal state of the random number generator.|
|value||Returns a random float within [0.0..1.0] (range is inclusive) (Read Only).|