Dsiplaying 3D Polygon Animations

Use examples to comprehensively explain the technology that allows us to display 3D polygon animations: graphics pipeline, e.g. modelling, lighting, viewing, projection, clipping, scan conversion, texturing and shading. Also research Radiosity & Ray tracing rendering techniques.

Graphics Pipeline
There are 7 stages to the graphics pipeline:

 

Lighting and shading - which makes lighting only at the vertices of the polygon which is being rendered.  There are three methods of shading, the first method is flat shading, this is simply one color for each polygon of the shape which is made up of squared polygons and will look more like a disco ball than a sphere, this means that the shape will look unrealistic, however this is a quicker way of processing the shape. The second method of shading is gouraud shading, this is kind of the same as flat shading however it calculates a color for each poly and created one for each verities  this means that there is a bit more color than flat shading, and it also looks a lot smoother, but this misses some of the effects in the lighting area. Finally, phong is the best way of shading, this is because it has more of a texture to it, it also looks more realistic than Gouraud and Flat shading, it is more accurate and brings out a more curvy sphere. However this slowers the processing speed for when you come to render it.

• Clipping - which can be used for a 2D and 3D graphic could mean that in a 2D graphic you may clip the bottom half of the image in which will avoid going over the memory which is needed, where as in a 3D graphic for example, in a town scene there will include the main models, shaded and texture data making the size of the file massive, to reduce this by clipping you can render the graphic to make it smaller and as well to make the program run faster.

• Projection - to make the camera smaller you can divide the x and y coordinates of each vertex by the Z coordinate which will represent the distance from the camera.

• Viewing - this is a very simple transformation by simply applying a scale and a bias which is multiplying width and adding the offset from the screen origin.

• Scan conversion - this is a wide subject in which it covers video projectors, television and cinema equipment. There are analogue and digital methods.

Texturing - this means the objects may look like they are bumpy, smooth, have color on them etc. Texturing is the wrap around the object which is like a cover for the object to make it look realistic, for example, the object may be one color at first and when rendered may look boring and plastic, however if you add a texture to it and then render it, it may look different and as though if you touched it, it will have a certain texture to it.

Radiosity

Radiosity describes a render which uses two types of lighting, theses lights are incident light and a reflective light, the reflective light simply reflects of the objects surface and the incident light hits onto the object. Radiosity is mainly used on interior designs.

Ray Tracing

Ray tracing is a type of render which renders out the image by casting out rays onto the scene, while this is being processed the color value of that pixel is being calculated, at the end of this technique it can produce very realistic renders, however it may take a long time to produce.

Use examples to comprehensively explain the following Geometric terms: vertices; lines; curves; edge; polygons; element; face; primitives; meshes; wire-frame; surfaces.

Vertices - this means corners of a polygon, the two lines that define a vertex and meet at each end point is a vertex.

Lines - 

Curves

Edge - 

Polygons - 

Element - 

Face - 

Primitives - 

Meshes - 

Wire-Frame - 

Surfaces -