Fusion is not a full-featured 3D application like Maya, Blender or 3Ds Max. But not every simple 3D task requires a full 3D pipeline. DaVinci Resolve and Fusion can provide a quick alternative for many tasks.
Card projects for compositing and motion graphics are a primary example. But sometimes you can even create some complete environments in Fusion.
This tutorial introduces the basic toolset to create and manipulate 3D objects. Shape 3D and Image plane are the most elementary objects to start from. You can create cubes, spheres, cylinders and more or place a picture into the 3D scene.
To transform any 3D object you can use the Bender node and the Displace 3D node. Bender will bend or twist an object along a defined axis. With Displace 3D, you can transform a 3D image based on image values of a 2D image.
Finally you can do a simple form of crowd replication in Fusion. Duplicate 3D and Replicate 3D can copy 3D objects and spread out the copies. With Duplicate 3D you decide on direction and distance of the copies. Replicate 3D takes an extra mesh input and spreads the copies along the intersections of that mesh.