3D modeling
Encyclopedia
In 3D computer graphics
3D computer graphics
3D computer graphics are graphics that use a three-dimensional representation of geometric data that is stored in the computer for the purposes of performing calculations and rendering 2D images...

, 3D modeling (also known as meshing) is the process of developing a mathematical representation of any three-dimensional
Three-dimensional space
Three-dimensional space is a geometric 3-parameters model of the physical universe in which we live. These three dimensions are commonly called length, width, and depth , although any three directions can be chosen, provided that they do not lie in the same plane.In physics and mathematics, a...

 surface of object (either inanimate or living) via specialized software
3D computer graphics software
3D computer graphics software refers to programs used to create 3D computer-generated imagery. This article covers only some of the software used.-Uses:...

. The product is called a 3D model. It can be displayed as a two-dimensional image through a process called 3D rendering
3D rendering
3D rendering is the 3D computer graphics process of automatically converting 3D wire frame models into 2D images with 3D photorealistic effects on a computer.-Rendering methods:...

or used in a computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

 simulation
Simulation
Simulation is the imitation of some real thing available, state of affairs, or process. The act of simulating something generally entails representing certain key characteristics or behaviours of a selected physical or abstract system....

 of physical phenomena. The model can also be physically created using 3D printing
3D printing
3D printing is a form of additive manufacturing technology where a three dimensional object is created by laying down successive layers of material. 3D printers are generally faster, more affordable, and easier to use than other additive manufacturing technologies. However, the term 3D printing is...

 devices.

Models may be created automatically or manually. The manual modeling process of preparing geometric data for 3D computer graphics is similar to plastic arts such as sculpting.

Models

3D models represent a 3D object using a collection of points in 3D space, connected by various geometric entities such as triangles, lines, curved surfaces, etc. Being a collection of data (point
Point (geometry)
In geometry, topology and related branches of mathematics a spatial point is a primitive notion upon which other concepts may be defined. In geometry, points are zero-dimensional; i.e., they do not have volume, area, length, or any other higher-dimensional analogue. In branches of mathematics...

s and other information), 3D models can be created by hand, algorithm
Algorithm
In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...

ically (procedural modeling
Procedural modeling
Procedural modeling is an umbrella term for a number of techniques in computer graphics to create 3D models and textures from sets of rules. L-Systems, fractals, and generative modeling are procedural modeling techniques since they apply algorithms for producing scenes...

), or scanned
3D scanner
A 3D scanner is a device that analyzes a real-world object or environment to collect data on its shape and possibly its appearance . The collected data can then be used to construct digital, three dimensional models....

.

3D models are widely used anywhere in 3D graphics
3D computer graphics
3D computer graphics are graphics that use a three-dimensional representation of geometric data that is stored in the computer for the purposes of performing calculations and rendering 2D images...

. Actually, their use predates the widespread use of 3D graphics on personal computer
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

s. Many computer games used pre-rendered images of 3D models as sprite
Sprite (computer graphics)
In computer graphics, a sprite is a two-dimensional image or animation that is integrated into a larger scene...

s before computers could render them in real-time.

Today, 3D models are used in a wide variety of fields. The medical industry uses detailed models of organs. The movie industry uses them as characters and objects for animated and real-life motion pictures
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...

. The video game industry uses them as assets for computer and video games. The science sector uses them as highly detailed models of chemical compounds . The architecture industry uses them to demonstrate proposed buildings and landscapes through Software Architectural Model
Software Architectural Model
An architectural model is a rich and rigorous diagram, created using available standards, in which the primary concern is to illustrate a specific set of tradeoffs inherent in the structure and design of a system or ecosystem...

s. The engineering community uses them as designs of new devices, vehicles and structures as well as a host of other uses. In recent decades the earth science
Earth science
Earth science is an all-embracing term for the sciences related to the planet Earth. It is arguably a special case in planetary science, the Earth being the only known life-bearing planet. There are both reductionist and holistic approaches to Earth sciences...

 community has started to construct 3D geological models as a standard practice.

Representation

Almost all 3D models can be divided into two categories.
  • Solid - These models define the volume of the object they represent (like a rock). These are more realistic, but more difficult to build. Solid models are mostly used for nonvisual simulations such as medical and engineering simulations, for CAD and specialized visual applications such as ray tracing and constructive solid geometry
    Constructive solid geometry
    Constructive solid geometry is a technique used in solid modeling. Constructive solid geometry allows a modeler to create a complex surface or object by using Boolean operators to combine objects...


  • Shell/boundary - these models represent the surface, e.g. the boundary of the object, not its volume (like an infinitesimally thin eggshell). These are easier to work with than solid models. Almost all visual models used in games and film are shell models.


Because the appearance of an object depends largely on the exterior of the object, boundary representation
Boundary representation
In solid modeling and computer-aided design, boundary representation—often abbreviated as B-rep or BREP—is a method for representing shapes using the limits...

s are common in computer graphics. Two dimensional surface
Surface
In mathematics, specifically in topology, a surface is a two-dimensional topological manifold. The most familiar examples are those that arise as the boundaries of solid objects in ordinary three-dimensional Euclidean space R3 — for example, the surface of a ball...

s are a good analogy for the objects used in graphics, though quite often these objects are non-manifold
Manifold
In mathematics , a manifold is a topological space that on a small enough scale resembles the Euclidean space of a specific dimension, called the dimension of the manifold....

. Since surfaces are not finite, a discrete digital approximation is required: polygonal meshes
Polygon mesh
A polygon mesh or unstructured grid is a collection of vertices, edges and faces that defines the shape of a polyhedral object in 3D computer graphics and solid modeling...

 (and to a lesser extent subdivision surfaces) are by far the most common representation, although point-based
Volume rendering
In scientific visualization and computer graphics, volume rendering is a set of techniques used to display a 2D projection of a 3D discretely sampled data set.A typical 3D data set is a group of 2D slice images acquired by aCT, MRI, or MicroCT scanner....

 representations have been gaining some popularity in recent years. Level set
Level set
In mathematics, a level set of a real-valued function f of n variables is a set of the formthat is, a set where the function takes on a given constant value c....

s are a useful representation for deforming surfaces which undergo many topological changes such as fluids.

The process of transforming representations of objects, such as the middle point coordinate of a sphere
Sphere
A sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...

 and a point on its circumference
Circumference
The circumference is the distance around a closed curve. Circumference is a special perimeter.-Circumference of a circle:The circumference of a circle is the length around it....

 into a polygon representation of a sphere, is called tessellation
Tessellation
A tessellation or tiling of the plane is a pattern of plane figures that fills the plane with no overlaps and no gaps. One may also speak of tessellations of parts of the plane or of other surfaces. Generalizations to higher dimensions are also possible. Tessellations frequently appeared in the art...

. This step is used in polygon-based rendering, where objects are broken down from abstract representations ("primitives") such as spheres, cones
Cone (geometry)
A cone is an n-dimensional geometric shape that tapers smoothly from a base to a point called the apex or vertex. Formally, it is the solid figure formed by the locus of all straight line segments that join the apex to the base...

 etc., to so-called meshes, which are nets of interconnected triangles. Meshes of triangles (instead of e.g. square
Square (geometry)
In geometry, a square is a regular quadrilateral. This means that it has four equal sides and four equal angles...

s) are popular as they have proven to be easy to render using scanline rendering
Scanline rendering
Scanline rendering is an algorithm for visible surface determination, in 3D computer graphics,that works on a row-by-row basis rather than a polygon-by-polygon or pixel-by-pixel basis...

. Polygon representations are not used in all rendering techniques, and in these cases the tessellation step is not included in the transition from abstract representation to rendered scene.

Notable Concepts and abbreviations

In 3D modeling there are recurring concepts which usually appear as abbreviations. Here are some of the most current:

CW, center of window, in reference to the visualization window.

VRP, view reference point.

VPN, view plane normal.

VUV, view up vector.

FOV, field of view.

VRC, view reference coordinates.

WCS, world coordinates system.

Modeling Process

There are Three popular ways to represent a model:
  1. Polygonal modeling
    Polygonal modeling
    In 3D computer graphics, polygonal modeling is an approach for modeling objects by representing or approximating their surfaces using polygons. Polygonal modeling is well suited to scanline rendering and is therefore the method of choice for real-time computer graphics...

     - Points in 3D space, called vertices, are connected by line segments to form a polygonal mesh. The vast majority of 3D models today are built as textured polygonal models, because they are flexible and because computers can render them so quickly. However, polygons are planar and can only approximate curved surfaces using many polygons.
  2. Curve modeling - Surfaces are defined by curves, which are influenced by weighted control points. The curve follows (but does not necessarily interpolate) the points. Increasing the weight for a point will pull the curve closer to that point. Curve types include Nonuniform rational B-spline
    Nonuniform rational B-spline
    Non-uniform rational basis spline is a mathematical model commonly used in computer graphics for generating and representing curves and surfaces which offers great flexibility and precision for handling both analytic and freeform shapes.- History :Development of NURBS began in the 1950s by...

     (NURBS), Splines, Patches and geometric primitives
  3. Digital sculpting
    Digital sculpting
    Digital sculpting, also known as Sculpt Modeling or 3D Sculpting, is the use of software that offers tools to push, pull, smooth, grab, pinch or otherwise manipulate a digital object as if it were made of a real-life substance such as clay....

    - Still a fairly new method of modeling, 3D sculpting has become very popular in the few short years it has been around. There are currently 3 types of digital sculpting: Displacement, which is the most widely used among applications at this moment, volumetric and dynamic tessellation. Displacement uses a dense model (often generated by Subdivision surface
    Subdivision surface
    A subdivision surface, in the field of 3D computer graphics, is a method of representing a smooth surface via the specification of a coarser piecewise linear polygon mesh...

    s of a polygon control mesh) and stores new locations for the vertex positions through use of a 32bit image map that stores the adjusted locations. Volumetric which is based loosely on Voxel
    Voxel
    A voxel is a volume element, representing a value on a regular grid in three dimensional space. This is analogous to a pixel, which represents 2D image data in a bitmap...

    s has similar capabilities as displacement but does not suffer from polygon stretching when there are not enough polygons in a region to achieve a deformation. Dynamic tesselation Is similar to Voxel but divides the surface using triangulation to maintain a smooth surface and allow finer details. These methods allow for very artistic exploration as the model will have a new topology created over it once the models form and possibly details have been sculpted. The new mesh will usually have the original high resolution mesh information transferred into displacement data or normal map data if for a game engine.


The modeling stage consists of shaping individual objects that are later used in the scene. There are a number of modeling techniques, including:
  • constructive solid geometry
    Constructive solid geometry
    Constructive solid geometry is a technique used in solid modeling. Constructive solid geometry allows a modeler to create a complex surface or object by using Boolean operators to combine objects...

  • implicit surfaces
  • subdivision surface
    Subdivision surface
    A subdivision surface, in the field of 3D computer graphics, is a method of representing a smooth surface via the specification of a coarser piecewise linear polygon mesh...

    s


Modeling can be performed by means of a dedicated program (e.g., form•Z
Form-Z
form·Z is a computer-aided design tool developed by AutoDesSys for all design fields that deal with the articulation of 3D spaces and forms and which is used for 3D modeling, drafting, animation and rendering.-Overview:...

, Maya
Maya (software)
Autodesk Maya , commonly shortened to Maya, is 3D computer graphics software that runs on Microsoft Windows, Mac OS and Linux, originally developed by Alias Systems Corporation and currently owned and developed by Autodesk, Inc. It is used to create interactive 3D applications, including video...

, 3DS Max, Blender
Blender (software)
Blender is a free and open-source 3D computer graphics software product used for creating animated films, visual effects, interactive 3D applications or video games. The current release version is 2.60, and was released on October 19, 2011...

, Lightwave
LightWave
LightWave 3D is a high end computer graphics program developed by NewTek. The latest release of LightWave runs on Windows and Mac OS X.- Overview:...

, Modo
Modo (software)
modo is a polygon and subdivision surface modeling, sculpting, 3D painting, animation and rendering package developed by Luxology, LLC. The program incorporates features such as n-gons, 3D painting and edge weighting, and runs on Mac OS X and Microsoft Windows platforms.-History:modo was created...

, solidThinking) or an application component (Shaper, Lofter in 3DS Max) or some scene description language (as in POV-Ray
POV-Ray
The Persistence of Vision Raytracer, or POV-Ray, is a ray tracing program available for a variety of computer platforms. It was originally based on DKBTrace, written by David Kirk Buck and Aaron A. Collins. There are also influences from the earlier Polyray raytracer contributed by its author...

). In some cases, there is no strict distinction between these phases; in such cases modeling is just part of the scene creation process (this is the case, for example, with Caligari trueSpace
TrueSpace
TrueSpace is a freeware 3D computer graphics and animation software developed by Caligari Corporation, bought-out by Microsoft. As of May 2009, it has been officially discontinued, but with some 'unofficial support' up to February 2010, at least.- History :The company was founded in 1985 by Roman...

 and Realsoft 3D
Realsoft 3D
Realsoft 3D is a modeling and raytracing application created by Realsoft Graphics Oy. Originally called Real 3D, it was developed for the Amiga computer and later also for Linux, Irix, Mac OS X and Microsoft Windows....

).

Complex materials such as blowing sand, clouds, and liquid sprays are modeled with particle system
Particle system
The term particle system refers to a computer graphics technique to simulate certain fuzzy phenomena, which are otherwise very hard to reproduce with conventional rendering techniques...

s, and are a mass of 3D coordinates which have either points
Point (geometry)
In geometry, topology and related branches of mathematics a spatial point is a primitive notion upon which other concepts may be defined. In geometry, points are zero-dimensional; i.e., they do not have volume, area, length, or any other higher-dimensional analogue. In branches of mathematics...

, polygon
Polygon
In geometry a polygon is a flat shape consisting of straight lines that are joined to form a closed chain orcircuit.A polygon is traditionally a plane figure that is bounded by a closed path, composed of a finite sequence of straight line segments...

s, texture splats, or sprites
Sprite (computer graphics)
In computer graphics, a sprite is a two-dimensional image or animation that is integrated into a larger scene...

 assigned to them.

Compared to 2D Methods

3D photorealistic effects are often achieved without wireframe modeling and are sometimes indistinguishable in the final form. Some graphic art software includes filters that can be applied to 2D vector graphics or 2D raster graphics
Raster graphics
In computer graphics, a raster graphics image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium...

 on transparent layers.

Advantages of wireframe 3D modeling over exclusively 2D methods include:
  • Flexibility, ability to change angles or animate images with quicker rendering of the changes;
  • Ease of rendering, automatic calculation and rendering photorealistic effects rather than mentally visualizing or estimating;
  • Accurate photorealism, less chance of human error in misplacing, overdoing, or forgetting to include a visual effect.


Disadvantages compare to 2D photorealistic rendering may include a software learning curve and difficulty achieving certain photorealistic effects. Some photorealistic effects may be achieved with special rendering filters included in the 3D modeling software. For the best of both worlds, some artists use a combination of 3D modeling followed by editing the 2D computer-rendered images from the 3D model.

3D Model Market

3CT
3CT
3CT is the process of creating 3D object libraries to be used in computer-aided design software. 3D catalogs facilitate the work of engineers, architects, designers and other users of CAD programs as they shorten considerably the time needed to draw and / or render a project.- Use :3CT is usually...

 (3D Catalog Technology) has revolutionized the 3D model market by offering quality 3D model libraries free of charge for professionals using various CAD programs. Some believe that this uprising technology is gradually eroding the traditional "buy and sell" or "object for object exchange" markets although the quality of the products do not match those sold on specialized 3d marketplaces.

A large market for 3D models (as well as 3D-related content, such as textures, scripts, etc.) still exists - either for individual models or large collections. Online marketplaces for 3D content, such as TurboSquid
TurboSquid
TurboSquid is a digital media supply company headquartered in New Orleans, Louisiana, United States. The company sells custom-built and stock 3D models used in 3D graphics to a variety of industries, including computer games, architecture, and interactive training...

, allow individual artists to sell content that they have created. Often, the artists' goal is to get additional value out of assets they have previously created for projects. By doing so, artists can earn more money out of their old content, and companies can save money by buying pre-made models instead of paying an employee to create one from scratch. These marketplaces typically split the sale between themselves and the artist that created the asset, often in a roughly 50-50 split. In most cases, the artist retains ownership of the 3d model; the customer only buys the right to use and present the model.

3D Printing

3D printing
3D printing
3D printing is a form of additive manufacturing technology where a three dimensional object is created by laying down successive layers of material. 3D printers are generally faster, more affordable, and easier to use than other additive manufacturing technologies. However, the term 3D printing is...

 is a form of additive manufacturing technology where a three dimensional object is created by laying down successive layers of material.

Human Models

The first widely available commercial application of human Virtual Models appeared in 1998 on the Lands' End
Lands' End
Lands' End is a clothing retailer based in Dodgeville, Wisconsin, that specializes in casual clothing, luggage, and home furnishings. The majority of Lands' End's business is conducted through mail order and Internet sales, but the company also runs more than a dozen retail operations, primarily in...

 web site. The human Virtual Models were created by the company My Virtual Model Inc. and enabled users to create a model of themselves and try on 3D clothing. There are several modern programs that allow for the creation of virtual human models (Poser
Poser
Poser is a 3D CGI rendering and animation software program optimized for models that depict the human figure in three-dimensional form, mostly used to pose and animate the figures in a similar way as a mannequin...

 being one example).

See also

  • 3CT
    3CT
    3CT is the process of creating 3D object libraries to be used in computer-aided design software. 3D catalogs facilitate the work of engineers, architects, designers and other users of CAD programs as they shorten considerably the time needed to draw and / or render a project.- Use :3CT is usually...

  • List of 3D modeling software
  • List of common 3D test models
  • 3D computer graphics software
    3D computer graphics software
    3D computer graphics software refers to programs used to create 3D computer-generated imagery. This article covers only some of the software used.-Uses:...

  • 3D scanner
    3D scanner
    A 3D scanner is a device that analyzes a real-world object or environment to collect data on its shape and possibly its appearance . The collected data can then be used to construct digital, three dimensional models....

  • Additive Manufacturing File Format
    Additive Manufacturing File Format
    Additive Manufacturing File Format is an open standard for describing objects for additive manufacturing processes such as 3D printing. The official ASTM F2915standard is an XML-based format designed to allow any computer-aided design software to describe the shape and composition of any 3D object...

  • Cloth modeling
    Cloth modeling
    Cloth modeling is the term used for simulating cloth within a computer program; usually in the context of 3D computer graphics. The main approaches used for this may be classified into three basic types: geometric, physical, and particle/energy.- Background :...

  • Computer facial animation
    Computer facial animation
    Computer facial animation is primarily an area of computer graphics that encapsulates models and techniques for generating and animating images of the human head and face. Due to its subject and output type, it is also related to many other scientific and artistic fields from psychology to...

  • Digimation
    Digimation
    Digimation is a provider of 3D digital content and 3D plug-in tools. The company, which was founded in 1992, relocated from New Orleans, Louisiana in 2009 and is headquartered in Lake Mary, Florida...

    's Library example
  • Digital geometry
    Digital geometry
    Digital geometry deals with discrete sets considered to be digitized models or images of objects of the 2D or 3D Euclidean space.Simply put, digitizing is replacing an object by a discrete set of its points...

  • Edge loop
  • Evolver
    Evolver (3D Avatar Web Portal)
    The web site Evolver claims to be the first solution to provide a central portal to design, manage and transport 3D digital avatars. Evolver enables social media experience through "avatars or user's representation" across applications which use them, such as virtual worlds, video games and social...

     is a portal, 3D modeler and market place for 3D characters
  • Geological modeling
    Geologic modelling
    Geologic modelling or Geomodelling is the applied science of creating computerized representations of portions of the Earth's crust based on geophysical and geological observations made on and below the Earth surface. A Geomodel is the numerical equivalent of a three-dimensional geological map...

  • Industrial CT scanning
    Industrial CT Scanning
    Industrial CT scanning is a process which uses X-ray equipment to produce three-dimensional representations of components both externally and internally. Industrial CT scanning has been used in many areas of industry for internal inspection of components...

  • Open CASCADE
    Open CASCADE
    Open CASCADE Technology is a software development platform for 3D CAD, CAM, CAE, etc. that is developed and supported by OPEN CASCADE SAS. It is available under the "Open CASCADE Technology Public License" which the developer claims to be . Despite this claim, it is not listed as compatible with...

  • Polygon mesh
    Polygon mesh
    A polygon mesh or unstructured grid is a collection of vertices, edges and faces that defines the shape of a polyhedral object in 3D computer graphics and solid modeling...

  • Polygonal modeling
    Polygonal modeling
    In 3D computer graphics, polygonal modeling is an approach for modeling objects by representing or approximating their surfaces using polygons. Polygonal modeling is well suited to scanline rendering and is therefore the method of choice for real-time computer graphics...

  • SIGGRAPH
    SIGGRAPH
    SIGGRAPH is the name of the annual conference on computer graphics convened by the ACM SIGGRAPH organization. The first SIGGRAPH conference was in 1974. The conference is attended by tens of thousands of computer professionals...

  • Stanford Bunny
    Stanford Bunny
    The Stanford Bunny is a computer graphics 3D test model developed by Greg Turk and Marc Levoy in 1994 at Stanford University.The Bunny consists of data describing 69,451 triangles determined by 3D scanning a ceramic figurine of a rabbit. The data can be used to test various graphics algorithms;...

  • Triangle mesh
    Triangle mesh
    A triangle mesh is a type of polygon mesh in computer graphics. It comprises a set of triangles that are connected by their common edges or corners....

  • Utah teapot
    Utah teapot
    The Utah teapot or Newell teapot is a 3D computer model which has become a standard reference object in the computer graphics community. It is a mathematical model of an ordinary teapot of fairly simple shape, which appears solid, cylindrical and partially convex...

  • Voxel
    Voxel
    A voxel is a volume element, representing a value on a regular grid in three dimensional space. This is analogous to a pixel, which represents 2D image data in a bitmap...

  • Marching cubes
    Marching cubes
    Marching cubes is a computer graphics algorithm, published in the 1987 SIGGRAPH proceedings by Lorensen and Cline, for extracting a polygonal mesh of an isosurface from a three-dimensional scalar field...

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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