Noise provides a flexible, powerful, and aesthetic source of variation that often works better than using a plain random number generator.
Random values are extremely common and important in procedural generation. Functions like
Math.random() are the common go-to for choosing random values, but in many situations they are hard to work with. Psuedo-random number generators are designed to provide independent, unpredictable, and evenly-distributed values. If we want related or repeatable random values we have to do extra work. If we want random variation with specific aesthetic characteristics we also have to do extra work.
What if the
random() function didn’t exist? How could you modify this example to get the same effect using the provided
randomValues array instead?
Noise functions are an alternative source of random values. Unlike the
random() function however, noise functions provide related, repeatable, and “good looking” random variation.
There are several common noise functions, each with different characteristics. The most widely known noise function is probably Perlin Noise, developed by Ken Perlin while working on visual effects for the amazing 1982 motion picture Tron. Ken later developed a similar but faster version called simplex noise. Other noise functions include Worley noise, developed by Steven Worley, and the simpler value noise.
Noise functions provide a “cloud” of random values that can be used in a wide variety of ways. Noise functions are frequently used in procedural texture generation and terrain generation, but their applications are not at all limited to those areas. Noise functions can be thought of as a lookup table of pre-generated random values that can be used in place of
random() in many cases. Noise functions are particularly well suited to adding small variations to create more natural feeling output.
Consider the code you would write to draw the blue squares above. You would need to provide several values for each square: horizontal position, vertical position, width, height, and color.
Where do those values come from? They could come from a few places.
|Hard Coded||You always want the same, specific value.|
|Parameters||You want to be able to control the value from a larger context.|
|random()||You want random variation.|
|noise(x)||You want random—but controlled—variation.|
noise() provide a source of variation, but
noise() provides much more control. The values from
random() the sizes of the boxes won’t be related at all. With
noise() we can control how quickly the size changes horizontally, vertically, and over time. If we sample a small area of the noise function the variation will be subtle and gradual. If our samples are far apart the variation will be be drastic, unpredictable and look a lot like
This example draws a big circle, and a line of smaller circles. Variation is created with the
random() function, which allows control over the amount of variation, and global (and fragile) repeatability via the random seed.
This example uses the
noise() function to create variation. It control over the amplitude, frequency, and character of the variation. It also provides independent (and robust) repeatability.
Compare the code and results of the two examples above.
|It’s easy to control the range of values provided by
||It is also easy with
|The values provided by
||The values provided by
|Repeatable results can be achieved with
||Achieving repeatable results with
noise(x) function returns values sampled from Perlin Noise. Perlin Noise provides random values with a particular aesthetic arrangement. The variation in Perlin Noise is band-limited: the frequency of values is predictable and even, without flat or noisy areas. The variation is also visually isotropic: it looks the same at different rotations. These characteristics make it a useful basis for many applications that require natural-feeling variation.
Other noise functions—like Worely and Value Noise—offer different aesthetic qualities, and it is quite possible to create your own noise function that looks the way you want. Most of the time you don’t need to create your own noise function to get a particular look. You can tweak the aesthetics of a noise functional by manipulating its values with math. The Terrain from Noise article on Red Blob Games is a good place to see some common techniques for shaping noise.
Noise functions take one or more coordinate arguments. These arguments specify a location in the noise cloud and the function returns the value found at that location.
This makes getting repeated results easy: every time you call
noise(x) with a particular argument, you get the same value back. This can be very useful. For example, in an animation you often need a value to stay the same from frame to frame.
random()does not accept coordinate arguments and returns a different random value every time.
noise(x)requires an coordinate argument and returns the same random value every time it is called with that argument.
This difference is the core reason why
noise(x) is so useful AND the core reason it can be confusing at first. Learning what values to pass to
noise() takes some practice.
By controlling what you pass to
noise(x), you can control the frequency of change in the returned values. This can be used to control how quickly values vary in space and time. With p5s Perlin Noise, you can also adjust the character of
noiseDetail(). You can scale and shift the values returned from
noise(x) to the range you need in the same way you shift values from
Many noise functions are multidimensional. The noise function in most programming libraries can take 1, 2, 3, or even more parameters. You can think of these parameters as specifying a multidimensional address in a “cloud” of values.
noise(x, y, z)
noise() function models an infinite cloud of predetermined random values. When you call
noise(x), you are asking for the value in the cloud at the coordinate
x. To create a noise function you need to build two things:
Different noise functions sove these problems in different ways.
How does the
noise(x) function work? Explore the underlying concepts by building a simplified noise function with pencil and paper.
noise() function takes up to three parameters:
noise(x,y,z). These parameters allow you to request values arranged in a three dimensional “cloud” of pseudo-random values.
When you call
noise(x) you have to pass in at least one parameter. This parameter specifies the location in the cloud of the value to return. You can think about
noise(x) as a lookup table:
noise(1) provides one value in the table and
noise(2) provides another.
Choosing appropriate parameter values takes some getting used to. You can pass in
millis() to get values that change over time. You can pass in XYZ coordinates to get values that change over space. These are very common cases, but really you can pass values from any range into
noise() and it will provide random values in return.
You can control the frequency of returned values by scaling the values you pass in for
// get a value that changes over time
n = noise(seconds);
// get a value that changes over time more slowly
n = noise(seconds * 0.1);
// get a value that changes over time more quickly
n = noise(seconds * 10);
Noise functions typically return values in the range of 0 to 1. Use multiplication and addition to shift values to the range you need. Be aware that while
random() provides evenly-distributed values, noise values are biased towards the middle. Also check the documenation for your noise function to understand the range it provides. In p5.js the range will differ depending on how you have configured it with
// scale values to sit between 10 and 20;
n = noise(frameCount) * 10 + 10;
You could also use
// map noise(frameCount) fromt he range [0,1) to the range [10 to 20)
n = map(noise(frameCount), 0, 1, 10, 20);
The noiseDetail() function allows you to control the “roughness” or “detail” of the noise returned. Detailed noise is achieved by adding layers of noise together.
Typically, each layer of noise is twice as detailed (higher frequency) and half as prominent (lower amplitude). These layers are sometimes refered to as “octaves” because their frequncies double each time, like musical octives.
By default, every time you restart your sketch the noise cloud is regenerated with a randomized seed. The noiseSeed() allows you to manually set the seed used for the noise cloud. This allows you to get the same values from
noise() after restarting your sketch.
The following study examples demonstrate using noise to introduce variation. Compare these examples to their counterparts in the Random Values chapter.
Using noise to determine the height of the buildings creates a skyline with tall and short buildings clustering together.
This example draws circles of varying sizes. Explore how passing different values to
noise() impacts what is drawn.
Using noise to control the lean of each blade of grass leads to a nice, natural-looking wind effect.
Explore the study examples above by completing the following challenges.
.001. Try changing the first constant to
.1. What happens? What happens when you change it to
.01. Change the second constant to
.01. What happens?
frequency. Change the values of these parameters to get a feel for how they affect the output. What happens when you use a very small value for frequency, such as
noise(x * frequency)to
noise(x * frequency, frameCount)? Make the change. Is that what you expected?
This week, focus on using the
noise() function. Use
noise() in a variety of ways. Use 1D, 2D, and 3D noise. Try using high, mid, and low frequency noise. Try using noise to control different things: position, size, color, rotation, etc. Think about tile graphics,
random(), and parameters while you work. Consider combining these concepts with
Make a program that generates treasure maps.