Wednesday, April 21, 2010

Animation Glossary : O and P

Welcome to Tej Kohli Animation Glossary
A generic term describing any item that can be inserted into and manipulated within a 3D scene. Models, lights, particle emitters and cameras are all objects.

Object file See: File format.

Origin See: Co-ordinate System, Axis.

Parent See: Hierarchy.

An area of a NURBS surface enclosed by a span square: the shape created by the intersection of four isoparms, two in the U direction, and two in the V direction.

Particle System
An animation system consisting of a large number of very small points whose behaviour is determined mathematically. A particle system typically consists of an emitter (which may be a point, surface or volume, and may emit particles directionally or in all directions) and a series of fields that determine the motion of those particles. Individual particles have a finite lifespan, and may possess attributes (such as colour, radius, and opacity) that vary over the course of that lifespan. Particle effects are commonly used to simulate fire, smoke, steam and other fluids, or to control complex animations such as crowd scenes.

Phong See: Shading.

Also known as image-based modelling, photogrammetry is the process of generating a fully textured 3D model from a series of photographs of a real object. Although it was once an expensive high-end technique, there is now a range of increasingly inexpensive photogrammetry software packages on the market.

A two-dimensional surface in Cartesian co-ordinate space. Essentially a flat sheet extending infinitely in all directions, a plane may be used to aid object manipulation, positioning and construction, and is not usually made visible in a final render.

A small piece of third-party software that is loaded into a 3D application in order to extend its functionality. Plugins commonly perform such specialist tasks as file conversion or data export, texture generation, and physics or fluid simulation. There are thousands of plugins currently available on the Internet, both commercially and as free downloads.

A one-dimensional point in coordinate space. Points can be linked up to form polygons, used as control
vertices for NURBS curves, or employed as nulls to control lights or cameras, amongst other functions.

A geometry element formed by connecting three or more points. A triangle, or three-point polygon, is the simplest form of polygonal geometry. Polygonal modelling is a fast, intuitive method of creating 3D objects, but does not easily generate smooth curved surfaces.

Post Processing
The manipulation of a rendered image, either to improve the quality of that image, or to create effects that cannot easily be achieved directly within the 3D software itself. Some 3D software packages can be set to automatically apply post-processing effects, such as motion blur or Depth of Field, after a frame is rendered.

A pre-generated list of settings for a particular 3D software package. Presets are usually used to control and customise properties such as rendering or lighting styles. Like plugins, they may either be commercial products, or freely downloadable from the Internet.

A time-saving method of checking the progress of a project by rendering it at a lower quality, resolution or frame rate than will be used for the final project.

A simple three-dimensional form used as the basis for constructive solid geometry modelling techniques. Typical primitives include the plane, the cube, the sphere, the cone and the torus.

Procedural Texture
A texture map that is generated by a mathematical function, rather than a real-world bitmap image projected over the surface of an object.

ProjectionThe process by which a twodimensional texture map is applied over the surface of a threedimensional object, as if it were an image projected from a slide projector. There are several common projection types, including Planar, Cubic, Spherical and Cylindrical. Which one is most appropriate depends on the type of map being projected, and the shape of the object it is being projected upon.

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