By adding the ProBuilder package to a new 3D project, we can enable ProBuilder's features.
ProBuilder allows a mesh to be added to the scene. Dragging faces using the ProBuilder Face-selection tool allows you to select and then move some of the faces to create a depression. The meshes next to those faces are then deformed, creating a slope so that there are no holes in the mesh.
Once the whole mesh has been colored with one color, selecting only some of the vertices (points) and applying another color results in smoothly painted areas around those vertices.
ProBuilder offers many more features, including creating objects by drawing a line-by-line polygon and texturing surfaces rather than just painting around vertices, as we did in this recipe. You can find links regarding the documentation of ProBuilder in the Further reading section.
