Modelling

 

Ideas and terms we need to master

Starting your 3D modeling journey is an exciting and rewarding experience. As you begin to learn and practice, there are essential terms you need to know and remember to grow your modeling skills. Use this resource to learn key terms and as a reference when creating your own 3D models. 

 
 
Polygon.png

Polygon geometry

A polygon is a three-four sided plane of geometry that makes a face on an object. Polygons are the most commonly used geometry type in 3D. While polygons are commonly used for all types of objects, in order to create very smooth surfaces with polygons means that you’d need to add a lot more geometry than you would with either NURBs or subdivision surfaces. 

NURBs surfaces

NURBS stands for non-uniform rational b-spline (NURBS). NURB splines are curves used to created smooth, minimal surfaces and geometry. NURBS are commonly used for very smooth objects because they don’t require as many points to create the same look as polygon geometry would. A NURBS surface always has four sides that are de ned by control points. 

Polygon_smooth.png

Subdivision surfaces

Subdivision surfaces, which are sometimes referred to as NURMS (non-uniform rational mesh smooth), are closely related to polygonal geometry. Subdivision surfaces use an algorithm to take polygon geometry and smooth it automatically. For example, in the image above you can see the polygon cage around the smoothed subdivision surface. You can think of a subdivision surface as a mix of polygonal and NURBs geometry. 


Face

When three or more edges are connected, the face is the filled space between the edges and makes up what is visible on a polygon mesh. Faces are the areas on your model that gets shading material applied to them. 

Vertex

A vertex is simply a point in 3D space. Connecting three or more vertices creates a face. These points can be manipulated to create the desired shape. 

Edge

An edge is the line created by connecting two vertices. Edges can be used to transform and de ne the shape of the model. 


 

TOPOLOGY

Whatever type of geometry you use it will either be created by NURBs, or points, edges, and faces. The way these components are connected together and the flow around the 3D object is the topology. You can think of topology as the type of polygon faces, the type of vertices and the ow of the edges. 

 

Triangle

A triangle is the simplest polygon that is made up of three sides or edges connected by three vertices, making a three sided face. When modeling, triangles are typically a polygon type often avoided. When creating complex meshes, triangles tend to pose a problem when subdividing geometry to increase resolution, and when a mesh will be deformed or animated. 

Quad

A quad is a polygon made up of four sides or edges that are connected by four vertices, making a four sided face. Quads are the polygon type that you’ll want to strive for when creating 3D models. Quads will ensure your mesh has clean topology, and that your model will deform properly when animated. 

n-gon

An n-gon is a polygon that is made up of ve or more sides or edges connected by ve or more vertices. It’s important to keep in mind an n-gon is typically related to a ve sided polygon, but it’s not limited to just ve sides. An n-gon should always be avoided, they often pose problems at render time, when texturing, and especially when deforming for animation. 

 

So why choose quads?

When modeling with quads, the wireframe will have a much cleaner look and the model will be easier to navigate and edit. When you spend hours working on a project, you deserve to show it off , but if the wireframe is messy you become very limited to what you can put out in the world.

When you use quads you create clean, sleek lanes of polygons that are easy to follow through the model and provide beautiful edge flows that can be easily modified by you or a team member. Someone can convert a model made up of quads to triangles easier than converting a model made up of triangles to quads. Having clean polygons also makes for a less distracting wireframe that you may want to overlay onto a clay shaded model or even a textured asset. 

If you plan on smoothing your geometry or using a quick smooth preview feature, triangles will produce anomalies across the surface of the mesh. Because of the uneven amount of vertices, the triangle can cause blemishes or pinch the geometry. This similar thing can happen to geometry created with n-gons. 

Quads produce cleaner deformations. Typically, artists will focus on areas where there will be a lot of bending and deforming, such as knees, elbows and wrists, and provide a little extra geometry that will bene t the rig and animation. With quads, this is easily accomplished by adding or manipulating edge loops.

If you have a cluster of triangles in this area, it is harder to add or remove loops that will help bene t the animator. With triangles, it is also harder to see a clean ow of geometry and they tend to produce sharp angles that can harm the mesh’s appeal. When it comes to animation appeal is important both to the model and the artist who provided the mesh for animation. 

Triangles are not a bad thing. They just have to be used strategically throughout your model. When using them on organic models, it is best to hide triangles where they will not be visible or in areas where very few deformations are happening.  

A good thing to keep in mind when working in quads is you can always convert it to triangles. There will be times when triangles will be preferred, an example of this is the final mesh of game assets or characters. In these instances most artists still prefer to work in quads and then convert their final model to a mesh built of triangles. 

 

Extrude

Extruding is one of the primary ways of creating additional geometry on a mesh. The extrude command allows you to pull out extra geometry from a face, edge or vertex. 

For instance, you can use the extrude command on the face of a simple cube to pull out the geometry needed to create fingers. These additional extrusions can be edited and manipulated just like any other area of the mesh. 


Edge Loop

An edge loop is a series of edges connected across a surface, with the last edge meeting the first edge, creating a ring or loop. Edge loops are especially important for maintaining hard edges in a mesh, and also for more organic models. Edge loops are helpful to add detail such as wrinkles or folds, they can also be used to help define how sharp an edge is. If an edge loop runs into a triangle, the loop has to end. This breaks the flow of the line and it’s no longer a loop. 

 

 
 
Arm Faces.png

Pivot point

The pivot point is the point on a 3D object where any rotation, scale, or moves that you do will occur from. This pivot point can be moved to any position on the model. For example, placing the pivot point on the hinges of a door will tell the computer where it should rotate from.


Beveling

Beveling is the process of chamfering, or creating rounded edges on a mesh. Beveling expands each vertex and edge into a new face. In the real world objects rarely have completely hard edges. Beveling helps to lose some of the computer generated look that comes with 3D modeling. 


Construction History

While you’re working on your 3D models you will likely use a wide range of tools to get the desired result. For example, you may need to extrude many different faces or bevel the edges of the model to create a particular shape. Most 3D applications keep track of all these actions in what is called the construction history. This displays a list of every different tools you’ve used on your 3D model in the order that you used them.

If you need to go back and adjust the settings of a tool you used, you can find it in the construction history. Keep in mind that as your construction history starts to stack up it will slow down your computer, so you will need to delete your construction history periodically. 


normals

Surface normals are used by your 3D application to determine the direction that light will bounce o of geometry. This is very helpful to get control over how the light reacts to certain materials on your 3D objects. 


Digital Sculpting

When creating 3D models in an application like Maya the process includes manipulating vertices and edges to get the desired look. While this works, it can be hard to get fine detail that is often required, especially in organic models. Digital sculpting works around this issue by allowing you to create your 3D meshes in much the same way as a traditional sculptor would. 

You can interactively push and pull areas of your model, and create details like wrinkles and scratches without ever having to select an edge or vertex. 

Often times a modeller will create the low resolution base mesh in a program like Maya, and import that into digital sculpting applications like ZBrush or Mudbox to be able to create those finer details. 

So you want to add that extra little detail to your model, you better use quads.
If you plan on taking your model into a sculpting application it is best to avoid triangles as much as possible.

Sometimes you may need to subdivide the geometry 4-5 times pushing your model to over a million polygons. This is why you want to work with a predictable quad- based mesh. This also helps build a lower resolution version and accent the model using edge loops. 

Texturing

 

Here we will go over some of the most common texturing terminology you are likely to encounter so you will be more comfortable when deciding which map to use or what was that term just referenced? 

To create a surface that resembles real life you need to turn to texture mapping. This process is similar
to adding decorative paper to a white box. In 3D, texture mapping is the process of adding graphics to a polygon object. These graphics can be photographs to original designs. Textures can help age your object, and give it more appeal and realism. 

 

UV Mapping

A 3D object has many sides and a computer doesn’t know how to correctly put a 2D texture onto the 3D object.

A UV map is basically the 3D model stretched out into a at 2D image. Each face on your polygon object is tied to a face on the UV map. Placing a 2D texture onto this new 2D representation of your 3D object is much easier. 


 
spec Map.png

Specularity

Specularity defines how a surface reflects light. It is basically the texture’s reflection of the light source which creates a shiny look. Having the right specularity is important in defining what the 3D object’s material is made from. For example, a shiny metal material will have high reflectivity, whereas a flat texture like cement will not. 

 

normal 02.png

Bump Maps

A bump map gives the illusion of depth or relief on a texture without greatly increasing render time. For example, the raised surface on a brick wall can be faked by using a bump map. The computer determines where raised areas on the image are by reading the black, white and grey scale data on the graphic. In other words, bump maps encode height information using black and white values. 

 
 

Normal Maps

A normal map creates the illusion of detail without having to rely on a high poly count. For example, a character can be detailed into a sculpting program like ZBrush, and all the information can be baked onto a normal map and transferred to a low poly character, giving the illusion of detail without increasing the actual poly count for the model. Game studios utilize normal maps often because they need to stay within a tight polygon budget, but still need a high level of detail. 

Normal maps use RGB values to signify the orientation of the surface normals. The information in the red, green and blue channels in the normal map corresponds with the X, Y and Z orientation
of the surface. Normal maps can typically capture more detailed information. 

Transparency Maps

Transparency maps are grey scale textures that use black and white values to signify areas of transparency or opacity on an objects material. For example, when modeling a fence, instead of modeling each individual chain link which would take a significant amount of time, you can use a black and white texture to determine what areas should stay opaque and what should be transparent.