3D Graphics

3D graphics means computer generated three-dimensional graphics. In 3D graphics, elements are visualized by creating three-dimensional models out of them. The final image is rendered from a virtual scene that utilizes several elements which are familiar from real life such as lights, materials and cameras. 3D graphics can be seen in multiple different forms such as an image, an animation or real time visualization inside of a computer game.

The creation of 3D graphics is a complicated process and therefore is, in my opinion, easier to understand when discussed in small pieces. The process of creating 3D graphics can be separated to the following tasks:

• Modeling
• Materials & Texturing
• Lighting
• Special Effects
• Animation
• Rendering

In the process of creating 3D graphics these separate tasks are often carried out roughly in the order of this list.

3D Modeling

3D modeling refers to the creation of the 3D model itself. A 3D model is a mathematical representation of an object. 3D modeling can be compared to sculpting. Artist builds or molds a 3D object by taking into account all different sides and angles.

Building blocks of 3D models

3D models consist of smaller elements (vertex, edge, face, polygon) which can be manipulated individually.

Vertex

Vertex is the smallest building block of a 3D model. Vertex is a point where two or more edges meet and where corners of faces or polygons meet. In a 3D model a vertex is shared between all connecting edges, faces and polygons. Transforming a vertex affects all connected edges, faces and polygons.

Edge

Edge is a line between two vertices. Edges are border lines of faces and polygons. In a 3D model an edge is shared between two adjacent faces or polygons. Transforming an edge affects all connected vertices, faces and polygons.

Face

Face is a triangle. Face is a surface between three corner vertices and three surrounding edges. Transforming a face affects all connected vertices, edges and polygons.

Polygon

Polygon is an even surface which has four or more corners and is made of two or more faces. A polygon is surrounded by edges and has a vertex in each corner. Animated high quality 3D characters are often made mostly of four-sided polygons. Polygons with 5 or more sides can cause problems in deforming surfaces such as a human face.

3D Modeling Techniques

3D models can be created in many different ways. The choice of modeling technique depends on the requirements and the complexity of the object. The following list describes some of popular 3D modeling techniques:

Loft

Loft is a modeling technique that uses lines. Loft object is created by using a line as a path and one or more lines as cross-sections.

Solid of Revolution

Solid of revolution is made of one line. The line represents a half cross-section of the object. Solid of revolution is created by revolving the line around a specified axis.

Boolean Operations

The starting point of Boolean operation is two overlapping 3D objects. Boolean operations are prone to error and the resulting geometry might have underlying problems.

Boolean operation has four possible results:

Union: Two 3D models are combined and the unnecessary geometry inside of the Models is removed.
Intersection:
Overlapping a part of the two 3D objects
Subtraction (A-B):
Object A is subtracted from object B
Subtraction (B-A):
Object B is subtracted from object A

Standard Primitives and Modifiers

Many 3D software packages include tools for creating standard objects such as boxes and spheres easily. One of the most simple 3D modeling techniques is to combine these standard objects to create complex 3D models. 3D Studio MAX includes standard objects such as sphere, cube and tube. These standard objects can be modified through their parameters (radius, height etc.) or through special modifiers (stretch, bend etc.). By combining several different standard objects and by modifying them, one can create complex 3D models.

Polygon Modeling

Complex objects are often modeled polygon by polygon. 3D software packages include many efficient tools for creating and manipulating polygons.

Polygon modeling tutorial (3DS MAX)

Subdivision Surface

Subdivision surface means a surface which is created by dividing the original 3D model into smaller polygons. At the same time 3D model's corners become rounder and the surface becomes smoother. Subdivision surfaces is a very popular modeling technique. The advantage of a subdivision surface is the fact that one can create a coarse 3D model which is then automatically subdivided into a smoother surface.

Subdivision surface modeling tutorial (3D Studio MAX)

Lines

3D object can be created by creating a cage of lines which can be converted to a 3D surface.

Line modeling tutorial (3DS MAX)

NURBS

NURBS stands for Non-Uniform Rational B-spline. In NURBS modeling, lines and surfaces are not manipulated by moving vertices, edges, faces or polygons. Instead NURBS surfaces and lines are manipulated by special control points.

You can read more about NURBS at Wikipedia.

Lighting

3D models and scenes are illuminated like real world objects. User creates light sources that are familiar from the real world such as sun, light bulb, spot light and so on. User can also apply lighting principles from real life such as three-point lighting.

Three-point lighting tutorial (3D Studio MAX)

Global Illumination

Global illumination is a process where computer calculates the bouncing of light. In real life light rays bounce from the surface they hit. Some of the light is absorbed by the surface and the rest is reflected. Reflected light rays pick up some of the color of the bouncing surface. Global illumination is a processor intensive task which can produce realistic illumination into 3D renderings.

Global illumination tutorial (3D Studio MAX Scanline renderer)

Materials and Texturing

Materials are applied to 3D models and they have a huge effect on how the final 3D model will look like. Materials have many surface characteristics which are used to define the final look of the model. These characteristics include for example:

• Surface color
• Transparency
• Glossiness
• Reflection
• Refraction
• Bump map
• etc.
  

Textures are often used in materials. Texture means a bitmap file which is applied to the 3D model through material and wrapped around the 3D model by using special mapping tools.

Special Effects

3D software packages often include tools designed for creating some specific effects such as fire or hair.These are the kind of effects that would be hard to create convincingly using the standard modeling, texturing, lighting and animation tools. Special effects that require a very specific tool are for example:

• Fire, Smoke Explosion
• Water
• Hair & Fur

Animation

3D graphics software is often called animation software. 3D graphics is extremely well suited for animation. Once the object is modeled in 3D, it's trivial to view it from any angle or distance, which makes the creation of animation fast compared to traditional 2D animation where each frame has to be drawn separately.

Character Animation

Creation of 3D character animation is a very complicated process which consists of four separate steps:

• Modeling the character
• Rigging the character
• Skinning the character
• Animating the character
  

Modeling the character

A character, especially a realistic one is one of the most challenging subjects to model believably. If a character is going to be animated, the task is even more challenging. When creating 3D models which are going to be deformed (such as a human hand), one must be extra careful when defining the structure of the surface. The structure (orientation and type of polygons) of the 3D model defines how well it is suited for an animation.

Rigging the Character

Character rigging means a process of creating the bone structure for a character. The bone structure is a set of helper objects that correspond to bones in real life. The bones (helper objects) will be animated and the character will move and deform accordingly. Bones itself won't show in the final rendered image.

Skinning the Character

Character skinning means the process of defining how exactly the character responds to the movement of the bones. In skinning process one goes through all the joints in the bone structure and carefully adjusts how the 3D model deforms while a certain bone is moving.

As an addition to bones there are also other special tools and modifiers designed to help in character animation. For example facial animation is often carried out by morphing the face between several predefined states.

Animating the Character

The last step in character animation is the animating itself. Animating requires a lot of skill and practice. An animator should understand at least the basics of character movement such as the concept of anticipation. Character animation process can be fluid when rigging and skinning are done with care.

Rendering

In 3D graphics rendering means the calculation of the final image from the scene that includes models, textures, lights, special effects and cameras. The final image will be 2D image made of pixels. Utilizing materials, lighting techniques, and renderer’s settings one can render multitude of different images from a single 3D scene.

Realistic rendering

Often the goal is to produce realistic rendering. For example in live action movies the goal is to render 3D effects as realistically as possible.

Diamond rendering tutorial (3SD MAX, Mental Ray)

Clay Rendering

When 3D modeler's present their modeling skills they often produce a clay render. Clay render means a rendering which looks like a picture of a clay model. The idea of a clay render is to bring out the form of the model.

Clay rendering tutorial (3D Studio MAX, Mental Ray)

Wire Rendering

The purpose of wire rendering is to reveal the polygon structure of the model. Wire rendering displays only edges of the polygons. Wire render and clay render are often combined.

Cartoon Style Rendering / Cell Shading

Cartoon style rendering means a material / rendering method that produces an image that looks like a hand drawn picture.

Cell shading tutorial (3DS MAX)

3D Software

Today's popular 3D software packages include for example:

• 3DS MAX, Maya, Mudbox (Autodesk)
  
• Houdini (Side Effects Software)
• LightWave 3D (NewTek)
  
• Softimage|XSI (Avid)
• Vue 6 (E-on Software)
  
• ZBrush (Pixologic)
• Cinema 4D (MAXON)
• Blender (Blender Foundation)

More complete list of today's 3D software packages at Wikipedia

Applications of 3D Computer Graphics

3D graphics has a wide variety of different applications such as:

• Movies, TV
• Computer games
• Industrial Design
• Internet
• Education
• Physics simulations