2. Displaying 3D Polygon Animations

To display 3D polygon animation you need a application (application programming interface) that actually display the 3D animation some of these are Direct3D and OpenGL. These programs create the shape that will then be displayed on the screen.The graphics pipeline is a stage that requires a three dimensional object to be shown on a two dimensional screen, to do this it gathered information on the vertices or the main control points of the 3D object and basically crops the 3D model so that it only displays what can actually be seen, for example, if we have a model of a shoe and we are looking at the shoe from a side on angle, the application programming interface will give only the information concerning the side visible of the shoe and will cut out the parts that should not be visible.there are a few different bits of information provided by the vertex which include its position on the x-y-z coordinates, the texture, reflectivity (or specular values) and the RGB (red, green, blue) values. The general primitives within a 3D model or 3D graphic are lines and triangles that create the shape and illusion of depth. however there are a few steps that the program does before simply creating and displaying the 3D model or graphic. These are; modelling, lighting, viewing, projection, clipping, viewport transformation, scan conversion, texturing & shading and then finally the display.



Each of these stages has very important jobs to create the image displayed.
First of all modelling. In the modelling stage the whole scene is generated using the vertices, edges and faces.
secondly the lighting stage. this is where the surfaces in the scene are lit accordingly to the position and location of the light sources in the scene.
Then there is the viewing stage. this is where the virtual camera is placed and based on the position of the camera the 3D environment is then transformed into a 3D co-ordinate system.After the viewing stage there is the projection stage. this is where the 3D illusion is created using perspective projection meaning that the more distant objects appear smaller.
the fifth stage is clipping. this is the stage where objects that are outside of view will not be generated, this isn't needed but helps improve overall performance of rendering.
Once the clipping process is done the next stage is viewport transformation. In this stage co-ordinates are given to the post-clip vertices, these co-ordinates will relate to the next stage which is called scan conversion. in the scan conversion stage rasterisation is used to determine the end pixel values.
once the scan conversion stage is done the individual pixels are given colours depending on their values givien from the rasterised vertices or from images created to be applied to the specific areas. this stage is the texturing and shading stage. then the final stage is the display where the final image of the scene with all the coloured pixels is shown on a 2D screen.