# Four is the magic number! The four basic operations of 3D modeling

As mathematics, also 3D modeling has its own *basic operations*, which are almost the same, no matter what software you work with. There are **four main operations** you have to master in your journey from newbies to experts.

Let's start with their names; I'm talking about **extrude**, **revolve**, **sweep** and **loft**. There are other features available in parametric modeling softwares, of course, but those four are the basic ones.

### 1. EXTRUDE

Let's start from the easiest one: **extrusion**! Its name comes from the same operation used in manufacturing. The peculiarity of extruded objects is a *constant section* (like in cylinders, cubes and prisms in general). What does it mean? Imagine to cut a cylinder into slices along its length, just like a carrot. All the slices – or *sections* – share the same diameter.

Extrude operation *requires a 2D sketch* – the constant section, which can be either a closed or an open profile (the first one creates a solid, the second one a surface) - *a vector as direction* (it is perpendicular to the plane where the profile was sketched on) *and a measure as height*.

Some pipes, filaments for 3D printers and some shapes of pasta are actually manufactured with extrusion machines.

### 2. REVOLVE

In geometry a revolved surface is created by *a curve (profile) rotating around a line (axis)*. The same definition is valid for 3D modeling too. A good example is a **donut**: you can create a donut-shaped solid by revolving a circle around a central axis; also a cylinder, as well as spheres, cones and so on. Many everyday things can be modeled by revolution, some examples are bottles, glasses, vases, plates, mugs (without handle!), bowls and so on.

**Revolve** operation *requires a 2D sketch as section* – it can be either an open or a closed curve – *a line as axis and an angle between 0° and 360°* - partial or full revolution.

### 3.SWEEP

**Sweep** operation is an *extrusion along a path*. Every continuous curve can be a path (a line, a square, a spline, an arc, a circle, etc.). An example of sweep is a picture frame: it has always the same section. Also handrails and some part of bycicles can be modeled using the sweep

**Sweep** *requires a 2D sketch as section and a curve as path*; the section can be either a closed or open profile (solid/surface resulting object).

### 4.LOFT

**Loft** operation is more complex; it *creates a “transition” solid or surface, interpolating many cross sections one after another in a specific order*. The word “*loft*” comes from shipbuilding techniques, think about how ships hulls are made, using sections and planking. What everyday things can we model using lofts? There are many, like handles for a door, a pot or a mug; the ergonomic grip of a toothbrush; the plastic shell of an hair dryer, even a plane!

A loft *requires at least two (or more) suitable profile curves as sections, lying on different planes*; depending on the section shapes, the result may be a solid body or a surface.

These four operations are ** all based on sketches**, they are, properly speaking, “

**”.**

*sketch-based features*There are some additional options for each feature, like control curves for loft and sweep and the taper for extruded objects. I will talk about those options in detail in the the future posts, for now feel free to practice a bit on the basic operations in the software that you prefer. I suggest you to have a look at **Autodesk Inventor** and **Fusion360**, because I am planning to post some tutorials using these two softwares.

The four basic modeling operations allow us to create a new object from sketches but also to modify existing ones by adding or subtracting volume to them (*boolean operations*). What?!

Don't worry, my next post will cover boolean operations, I will explain you how to add and remove volume after the creation of a basic model.

Thanks everyone for reading this post, stay tuned for the next one!

*Note: all the images in this post were created by the author using original material or images found on google and labeled as freely reusable.*

*If you want to know a bit more about 3D parametric modeling, you might be interested in reading my previous posts (they provide an introduction to this modeling approach):*