HA4 Task 4 - Mesh Construction

How are 3D models constructed? Describe and explain the different modelling techniques available to a 3D designer.

                                                                                                                                                                  


Polygonal Modelling:

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.

A polygon mesh is a collection of vertices, edges and faces that defines the shape of a polyhedral object in 3D computer graphics and solid modeling. The faces usually consist of triangles, quadrilaterals or other simple convex polygons, since this simplifies rendering, but may also be composed of more general concave polygons, or polygons with holes.

Information:

http://en.wikipedia.org/wiki/Polygon_mesh

http://en.wikipedia.org/wiki/Polygonal_modeling

                                                                                                                                           


Modelling with Primitives:

The most common 3D primitives are cubes, pyramids, cones, spheres, and tori. Like 2D shapes, these primitives can have a resolution level assigned to them so that you can make them look smoother by boosting the number of sides and steps used to define them.




Primitives are best suited as building blocks for more complex forms or for use in your scene's background, where any extra detail will be lost anyway. Also, primitives can be very useful as foreground objects when they're altered through the use of transforms and modifiers

 Some programs may offer an array of additional, more sophisticated primitives that may be better suited to foreground use because they offer beveled or rounded edges instead of that "chopped-off 3D look"

 A number of these extended primitives would be a real chore to create from scratch, so they can be a time-saver in that regard as well.

 
 Information:

http://www.peachpit.com/articles/article.aspx?p=30594&seqNum=5

                                                                                                                                             

Box Modelling:

This is a technique that is used in 3D modelling where the model is created by modifying primitive shapes to create a rough draft of the final model, in most cases. A primary function of box modeling involves extruding and scaling the faces, which are the flat planes that make up a model.

This image shows how box modelling works, It starts of as a box and using the subdivide and extrude tools, sculpts the box into a tangible face.




                                                                                                                                           

Extrusion Modelling:

In extrusion modeling, the modeler starts with a small portion of a model—which could be a polygon, or an edge, or even just a point—and works outward from this starting point using extrusion and other tools.



Through extrusion a modeler manipulates the 3D mesh by either collapsing a face in upon itself (to create an indentation), or by extruding the face outward along its surface normal—the directional vector perpendicular to the polygonal face.

Extruding a quadrilateral face creates four new polygons to bridge the gap between its starting and ending position.

Information:

http://3d.about.com/od/Creating-3D-The-CG-Pipeline/tp/Polygonal-3d-Modeling-Common-Box-And-Edge-Modeling-Workflows.htm

                                                                                                                                           

Sketch Modelling:

Sketch based modeling is differentiated from other types of 3D modeling by its interface - instead of creating a 3D model by directly editing polygons, the user draws a 2D shape which is converted to 3D automatically by the application.



Sketch based modeling is primarily designed for use by persons with artistic ability, but no experience with 3D modeling programs. Curvy3D and Teddy, below, have largely been designed for this purpose. However, sketch based modeling is also used for other applications. One popular application is rapid modeling of low-detail objects for use in prototyping and design work.

Information

http://en.wikipedia.org/wiki/Sketch-based_modeling

                                                                                                                                            

3D scanners:

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



Many different technologies can be used to build these 3D scanning devices; each technology comes with its own limitations, advantages and costs. Many limitations in the kind of objects that can be digitized are still present, for example, optical technologies encounter many difficulties with shiny, mirroring or transparent objects. For example, Industrial computed tomography scanning can be used to construct digital 3D models, applying Non-destructive testing.



Collected 3D data is useful for a wide variety of applications. These devices are used extensively by the entertainment industry in the production of movies and video games.

Information:

http://en.wikipedia.org/wiki/3D_scanner