The concept of 3D printing has been around since the 1980s, but only recently has the technology become accessible to the mainstream consumer. 3D printers work by taking a prebuilt computer model of a part, slicing it into small sections or layers, and then physically creating those slices using a variety of materials. Most commercially available printers need the initial computer model to be saved in the STL (stereolithography) format. This file only contains the data needed to create the surface geometry of an object – attributes such as color, texture, or relative associations are not stored. Additionally, the STL format does not have any scale information so dimensioning units are arbitrary.
Fortunately, a large percentage of software packages that can create 3D models will have the option to save designs in the STL format. There are also many free and easy-to-use 3D drawing programs available for a variety of computer platforms, which you can find by conducting a quick search online – here is a list of 3D software to get you started.
So, how do you find the right modeling program to fit your needs?
Creating 3D Models
The objective of creating 3D models is to have a digital representation of a physical object in the computer – a collection of points, or vertices, that outline the shape and a set of polygons that connect the vertices to form the surface. Models can also be represented by a set of user-defined curves that the computer fills in to form a 3D surface. While there are a number of techniques used in 3D modeling, they can be broken down into two main methods:
- Physical object required: In this method, also known as 3D scanning, a physical object is precisely scanned with a machine and its shape is converted to points and surfaces by the computer. This method can be limited by the resolution of the scanner and also relies on the presence of a physical object. Scanning is often the preferred 3D modeling method when a high level of photo-realism is required.
In the movie The Curious Case of Benjamin Button, where the lead character (Brad Pitt) aged in reverse throughout the film, 3D scanning was used to superimpose a digital version of Pitt’s head at various ages onto the bodies of people of different sizes, rather than using prosthetic makeup.
- Physical object not required: In the second method, a program is used to produce and orient the vertices and surfaces or curves to form the desired shape. This can be done in a polygonal modeling technique, or by “lofting” mesh between two or more Bezier curves (also known as splines), or even by user-defined parameters and algorithms. There are multiple methods to do this: box modeling, edge/contour modeling, NURBS/spline modeling, procedural modeling, and image based modeling are all common techniques, to name a few.
Constructing the model from scratch can be time consuming, but can produce parts and assemblies that are much more complex like eyewear, clothing, and even prosthetics. Methods like procedural modeling are often used for organic constructs like trees and foliage, where there is almost infinite variation and complexity that would be very time consuming (or impossible) to capture by hand.
Choosing a 3D modeling program
Even in the free, open source versions of programs available, there is a large variation in complexity and required skill levels. For those without a drafting or engineering background, the concepts and inner workings of how some of these applications are organized can be daunting or frustrating. Visualizing this new 3D world on a 2D computer monitor can still cause heads to spin.
One solution is to start with a simple program such as Google’s SketchUp to learn the basics. Users are presented with basic tools to create edges and faces, and a simple process to “push” or “pull” those faces into a 3D object. There are a couple of more advanced free programs to choose from as well:
- Blender: Blender is a powerful CAD program and animation suite with features found in many commercial applications. It supports the entirety of the 3D pipeline – modeling, rigging, animation, simulation, rendering, compositing, and motion tracking.
- BRL-CAD: This is a powerful cross-platform open source solid modeling system. The US military uses this tool to assess weapons systems for vulnerabilities.
These applications have the same basic concepts, but are different in how shapes are created and manipulated. More complex programs will allow users to create individual parts and then to mate those parts together into a final assembly, like the racecar below.
Autodesk 3D Modeling Image from AR Blog
Of course, there are also many commercially available programs, the largest being the AutoDesk family. Packages can vary in price, ranging from the inexpensive Alibre at $1000, to the mid-range Solidworks at $4000, to the top of the line AutoDesk package at $6300. Most commercial programs are also available as annual subscriptions. You may want to consider these subscriptions, since they include free upgrades, and they can save money in the long term. The more expensive commercial programs aren’t required to produce models for basic 3D printing, but they do have features that can be beneficial to some users.
The advent of commercially available 3D printers has certainly created a stir in the consumer marketplace, with some analysts even envisioning households eventually manufacturing required small parts instead of purchasing them. Unfortunately, there is a gap in the process, which is the need to use 3D modeling software to create the required STL files. Thankfully, easy-to-use and free solutions are available to the beginner or hobbyist to bridge this gap. As the popularity of 3D printing continues to increase, more user friendly programs and self-help options will be created to match the demand, truly bringing the reality of 3D printing to the masses.
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