3D modeling is a vast and relatively new field – the first 3D graphics appeared only in 1972. However, it’s growth has been tremendous, with 3D modeling being used in industries ranging from gaming and film to architecture and engineering. It affects all walks of our lives, as all the films we see and all material goods we use have 3D modeling involved in their making. Here, I discuss about the basics of 3D modeling.
What is 3D modeling?
3D modeling is the process of developing a mathematical representation of an object or only it’s surface in 3D with the help of various specialized software. The representation is called a 3D model. It can be used as a 2D image through a process called 3D rendering (primarily used in the game design and animation) and in a computer simulation to simulate the performance of the model (engineering). Furthermore, 3D models can also be printed with the help of 3D printers.
(Image credit – upwork)
Types of 3D modeling –
There are 2 major types of 3D modeling –
1 Solid Modelling –
In technical terms, a solid model is a complete mathematical representation of an object. While this may seem to be difficult to understand, in simpler terms solid modeling creates a virtual 3D representation of objects for machine design and analysis.
A solid model generally consists of a group of features, added one at a time, until the model is completed. Solid models make it easy to determine mass properties of an object. Additionally, mass properties are properties of an object which change with a change with it’s mass and mass distribution(density, the center of gravity). Further, sections can be easily cut through it to study and define internal details.
There are various methods to create and represent solid models. A few of these methods are –
a) Constructive Solid Geometry – In CSG, a solid object is constructed by combining some basic solids via Boolean operations. The simplest solid objects, from which solid models are made, are known as primitives. These primitives are arranged in a tree structure using Boolean operations to construct a model. It is quite an easy method for modeling objects. The structure is concise and relatively less storage is required for a CSG model. However, CSG is slow in displaying the objects.
A typical CSG tree
b) Sweep Representation – In sweep representation, a solid is defined in terms of volumes swept out by 2 or 3 dimensional laminae as they move along a curve, also called a path. Most commercial CAD systems provide (limited) functionality for constructing swept solids.
Creation of a toroid by the sweep
c) Primitive Instancing – Primitive instancing is based on the definition of object families, where each object is distinguishable by a few parameters. Each family is called general primitive and each object is called a primitive instance. For example, a family of bolts is a generic primitive, and a single bolt specified by a particular set of parameters is a primitive instance. While it is a very simple method of generating models, the main disadvantage is the limited number of object families.
Please note that these are only a few solid modeling methods. Most software provides multiple of these methods.
Solid modeling is mostly used in engineering and medical fields. In engineering, parts and machines are modeled to be studied and to run simulations on. The models are also used for 3D printing. In medical, CAT and MRI scans create solid models of internal body organs. This process is called volume rendering.
2 Surface Modelling-
Surface modeling represents the boundary of the object and does not define it’s volume.
If you draw a circle and extrude the surface area, the end result will be a solid cylinder, with properties such as mass, the moment of inertia, volume etc. This is an example of solid modeling. Now instead, if you just extrude the circumference of the circle, the result will be a hollow cylinder, without any wall thickness. This is an example of surface modeling. This a good example illustrating the difference between solid and surface modeling. Additionally, sectional views cannot be obtained in surface models.
Almost all visual models used in games and films are surface models. It is widely used in architectural renderings too. Further, they are of use in engineering too. Surface models are used in aerodynamic analysis and sheet metal working, where mass properties are not very important.
It uses Bezier curves and B-splines to generate surfaces.
(Typical Bezier curve used for surface models)
Software for 3D Modelling –
There are mainly 3 categories of 3D modeling software –
1 Entertainment – Used in game design, animation, and special effects. They are mostly surface modelers. Some examples are Maya, Blender etc. Maya is the industry standard software, while Blender is the best open source software.
2 Manufacturing – Used for designing machine components and parts. Many of these software also have the capability of running simulations on objects designed. They are generally hybrid modelers, allowing for both solid and surface modeling. Some examples are Solidworks, CATIA, Siemens NX etc. SolidWorks is the simplest to use out of all the commercial options. Unfortunately, there are no good open source options in this category.
3 Architecture and construction – These software specialize in creating architectural renderings of a house’s interiors and exteriors. The best software in this category are Revit and ArchiCAD.
There are also some tools which can be used by people across the 3 categories. SketchUp is the most popular software in this segment. However, for advanced applications, people tend to stick to products designed for their category.
Personally, I prefer to work with SolidWorks, since I am a mechanical engineering student, but you can choose any tool based on your preferences.
I am a student of Mechanical Engineering (Undergrad 6th sem). My interests lie in 3D modelling, technology, writing and football. Feel free to ask me anything !