The BY-GEN addon generates or modifies a mesh with use of multiple modifiers. Because only modifiers are used, it is a non-destructive workflow. It is also called a generative modeling style. We can expect a new wave of modeling styles like this in 2019.
Interesting to know is that curtisjamesholt was first featured on Blenderartists.org and the question “How did you do that” followed. He was inspired by a very popular tweet by Emiliano Colantoni. And Curtis writes answers with an interesting post here. I am quoting one sentence here below.
I think one of the reasons why there’s more of it now is because the potential of procedural techniques is becoming much more obvious in digital industries, especially for VFX and gaming.curtisjamesholt on blenderartists.org
A few notes about the addon before you start
Don’t expect to press a button and have a perfect result. In most case you need to tweak the mesh or the modifier stack. This, to set expectations. If you get familiar with the addon, it can be a great tool. Another use-case of the addon is to learn from it and make your own modifier stack.
Maybe an idea to start for example is with the default cube, subdivide it in Edit mode two times. Then in the Modify panel (N-Panel > BY-GEN), choose: Organic Shell and Musgrave. You will get a result as shown in the cover of this article. To get the inner cube you need to play with the modifier stack.
QuickStart on how to use the BY-GEN addon.
The BY-GEN has three panels. The first is to generate mesh, the second to modify existing mesh (not yet modified). The last panel has two options and that is to apply the whole modifier stack and purge textures. That’s pretty much you need to know.