Flow field

September 22, 2018
javascript physics visual creative

One of the most popular coding exercises out there is a Flow Field. The main idea behind that is to generate a vector field randomly, which is very often based on Perlin Noise. Then a set of particles are placed on the vector field and they are free to move along it, where the vector field determines the force placed upon the particle. To make things more dynamic and alive it is possible to vary the vector field over time. The result is something like the interactive animation written in JavaScript and using the p5js library, as shown below.

The Vector Field is drawn on the screen to better illustrate how it works. It can be disabled using the checkbox Show Field, which will generate a much more pleasing visualization. The Wrap Noise checkbox control if the vector is symmetrical along the axes or not. Having it symmetrical makes it more well behaved overall, where the flow connects across the borders. This makes possible for a particle that leaves the screen on the right, to continue its journey when it appears on the right. Now, if this option is turned off, the field on the left may be pointing in the opposite direction that the particle came from, possibly in a way that it will get stuck in the borders.

The slider that shows 500 Particles is auto explanatory, it shows the number of active particles. Another control is the Noise Level slider. This one control how noisy the vector field is. The smaller this value is, the straighter the trajectory will be. On the other hand, a high value makes the field very noisy which will make the particles to behave very errantly. Finally. the Flow Rate determines how fast the field changes in function of time. Have it set to 0 and the flow will be static. If this is set to its maximum value then the particles will switch its direction very often, even if the field is not noisy.

An interesting aspect that I implemented here is different properties for the particles. The attent reader may have noticed that some particles behave slightly different than other. With the blue and green ones having a more straight trajectory, while the pink and orange ones making more shape turns. This is due to differences in mass between the particles. The lighter ones undergo a more rapid change in velocity while the heavier ones may need a lucky sequence of vectors to make it turn a sharp 90 degrees turn.

Writing this was pretty much my first experience with JavaScript in a just for fun context. This project also got me willing again to do some creative coding, so expect to see some more around. Check out the Dancing room for a similar project and the creative tag.

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