HA7 Task 2

Displaying 3D Polygon Animations:

It can be displayed as a two-dimensional image through a process called 3D rendering or used in a computer simulation of physical phenomena. The model can also be physically created using 3D printing devices.

API

The game engine uses software known as an application programming interface or API, which is a set of routines, protocols, and tools for building software applications

Most operating environments, such as MS-Windows, provide an API so that programmers can write applications consistent with the operating environment. Although APIs are designed for programmers, they are ultimately good for users because they guarantee that all programs using a common API will have similar interfaces. 

Direct3D

An API for manipulating and displaying three-dimensional objects. Developed by Microsoft, Direct3D provides programmers with a way to develop 3-D programs that can utilize whatever graphics acceleration device is installed in the machine. Virtually all 3-D accelerator cards for PCs support Direct3D.

Another 3-D standard offering similar functionality is OpenGL.

OpenGL

A 3-D graphics language developed by Silicon Graphics. There are two main implementations: Microsoft OpenGL, and Cosmo OpenGL. Microsoft OpenGL is built into Windows NT and is designed to improve performance on hardware that supports the OpenGL standard. Cosmo OpenGL, on the other hand, is a software-only implementation specifically designed for machines that do not have a graphics accelerator.

Graphic Pipeline:

In 3D computer graphics, the graphics pipeline or rendering pipeline refers to the sequence of steps used to create a 2D raster representation of a 3D scene. Plainly speaking, once a 3D model has been created, for instance in a video game or any other 3D computer animation, the graphics pipeline is the process of turning that 3D model into what the computer displays. In the early history of 3D computer graphics, fixed purpose hardware was used to speed up the steps of the pipeline through a fixed-function pipeline. Later, the hardware evolved, becoming more general purpose, allowing greater flexibility in graphics rendering as well as more generalized hardware, and allowing the same generalized hardware to perform not only different steps of the pipeline, like in fixed purpose hardware, but even in limited forms of general purpose computing.


Stages of the graphics pipeline


3D geometric primitives

First, the scene is created out of geometric primitives. Traditionally this is done using triangles, which are particularly well suited to this as they always exist on a single plane.

https://3dtin.files.wordpress.com/2011/09/screen_shot_2011-09-08_at_6-05-37_pm-scaled500.png?w=494&h=407

Modelling and transformation

Transform from the local coordinate system to the 3d world coordinate system. A model of a teapot in abstract is placed in the coordinate system of the 3d world.

http://techpubs.sgi.com/library/dynaweb_docs/0650/SGI_Developer/books/VolumizerPG/sgi_html/figures/ExtendingPrimitives.gif

Camera transformation

Transform the 3d world coordinate system into the 3d camera coordinate system, with the camera as the origin.



Lighting

Illuminate according to lighting and reflectance. If the teapot is a brilliant white color, but in a totally black room, then the camera sees it as black. In this step the effect of lighting and reflections are calculated.

Projection transformation

Transform the 3d world coordinates into the 2d view of the camera, for instance the object the camera is centered on would be in the center of the 2d view of the camera. In the case of a Perspective projection, objects which are distant from the camera are made smaller. This is achieved by dividing the X and Y coordinates of each vertex of each primitive by its Z coordinate (which represents its distance from the camera). In an orthographic projection, objects retain their original size regardless of distance from the camera.

http://www.songho.ca/opengl/files/gl_transform09.png

Clipping

Geometric primitives that now fall completely outside of the viewing frustum will not be visible and are discarded at this stage.


Scan conversion or rasterization

Rasterization is the process by which the 2D image space representation of the scene is converted into raster format and the correct resulting pixel values are determined. From now on, operations will be carried out on each single pixel. This stage is rather complex, involving multiple steps often referred as a group under the name of pixel pipeline.

Texturing, fragment shading


At this stage of the pipeline individual fragments (or pre-pixels) are assigned a color based on values interpolated from the vertices during rasterization, from a texture in memory, or from a shader program.

Sources:

API - http://www.webopedia.com/TERM/A/API.html
Direct 3D - http://www.webopedia.com/TERM/D/Direct3D.html
OpenGL - http://www.webopedia.com/TERM/O/OpenGL.html
Graphic Pipline - https://en.wikipedia.org/wiki/Graphics_pipeline