Object Orientated Data

1. Object Orientated Data Topic 5: Multimedia Technology

2. Object Orientated Data Types • Created on a computer not by sampling real world information • Details are stored on the attributes (properties) of each object that is stored in the file. • Each object can be altered by changing its attributes…

3. Examples • Text • A character in a text file can be given a different size, colour or font • MIDI music • A note in a MIDI sound can be given a different volume, length or pitch • Drawing • A shape in a drawing can be given a different size or fill colour • 3D image • An object in a 3D image can be given a different location, rotation or texture

4. Object Orientated Data Files • All data is stored as a group of objects within a file • Each object can be edited individually without affecting any others • All aspects of each object are decided by its properties (attributes) • These files are basically a collection of objects with details about them. This means they can be stored as plain text files.

5. Input of Object Orientated Data Although OOD can be created using nothing but a simple text editor there are specialised input devices to help users create and edit them • You are already familiar with a keyboard for entering text

6. Specialised Input Devices • To create drawings or 3D images a graphics tablet • More accurate than using a mouse • To enter musical notes a MIDI keyboard • Easier than using a computer keyboard • 3D digitisers can measure points on an object and generate a 3D object from data

7. Output / Display of OOD • The quality of object orientated data is very dependant on the hardware & software used to output it. • For example: • Web browser setting can cause the same text to be displayed in different ways on different computers • Different graphics cards for rendering 3D images on screen may produce different quality and support different features

8. Rasterisation • Converting an object orientated file to a discrete (bitmap) file type • The equivalent of capturing data (as with digitised sound or bitmap image) • Difference is no input hardware is required • All the information about each object is lost. • Attributes can no longer be altered

9. Converting from OOD

10. Object Orientated Data Topic 5: Multimedia Technology

11. Recap • Object Orientated Data • All data is stored as a group of objects within a file • Details are stored on the attributes (properties) of each object that is stored in the file. • Each object can be edited individually without affecting any others • These files are basically a collection of objects with details about them. This means they can be stored as plain text files.

12. Vector Vs Bitmap Can be scaled to large sizes, keeping original quality. Scaling causes pixellation. Only the image as a whole can be edited. Individual objects can be edited. Are easily converted to bitmap formats. Are very difficult to convert to vector formats File sizes are relatively small. File sizes can be large. Images can be very realistic (e.g. digital photograph). Difficult to create realistic images

13. Vector Vs Bitmap Size of image can be increased keeping quality and file size the same. Increasing the image size needs re-sampling and increases the file size. Only individual objects can be edited (it is sometimes impossible to edit only part of the object). Pixel level editing is allowed - allowing effects such as spray paint, blur, effects and so on. Same appearance in all systems, regardless of hardware or software. Dependent on output hardware or software for appearance & quality. Suitable for natural, hand-drawn looking, realistic images. Suitable for graphic, unrealistic images and designs.

14. Attributes • Attributes are the properties that determine what and how objects will appear • These files can include a bitmap as a separate object…

15. Object 5 Object 6 Object 7 Object 2 Object 3 Object 4 Object 1 Objects & Attributes

16. Object Orientated File Formats Drawing : SVG 3D : VRML/WML Synthesised sound : MIDI

17. Drawing File Formats Scalable Vector Graphics (SVG) • A format for encoding vector graphics in XML (eXtensible Markup Language) • Designed to provide vector graphic content in Web pages. • Viewing: • You must have an SVG capable Browser, a plug-in for your browser or a stand-alone SVG viewer.

18. Additional Attributes for 3D images • Surface texture – give surface definition • Shadow – simulates direction of light • Angle of rotation (to view from different angles) • Z coordinate File format for 3D vector imag:VRML/WML

19. 3D Image File Formats Virtual Reality Modelling Language/ World Representation Language (VRML/WRL) • Standard for describing interactive 3D objects and worlds • Capable of representing static and animated 3D & multimedia objects with hyperlinks to other media such as text, sounds, movies and images

20. VRML/WRL • Creating/authoring VRML • Authoring tools vary from expensive 3D modellers to freeware utilities • WRL are text based so any text editor can be used. The suffix ‘.wrl’ is used to save • Viewing VRML • A VRML plug-in is needed

21. VRML/WRL • Navigating in VRML • Each player has slightly different features • Most have at least three navigation modes: • Walk – Allows you to move around • Fly – move around, up and down • Examine – rotate whole VRML world viewing from different angles

22. Synthesised Sound Data (MIDI) • MIDI is a standard that was created to allow musical instruments to be able to communicate with each other • A MIDI file consists of Channels (up to 16) • Each channel consists of a sequence of messages including: • Start of a note • Channel to use • Pitch of the note • Volume to play it at • End of note

23. Synthesised Sound Data (MIDI)

24. Advantages Smaller file size All aspects of music can be edited Effects can be applied to individual instruments There is no interference from the recording Disadvantages Never sounds as realistic as digitised sound Dependent on soundcard for quality Does not contain vocals Fewer effects can be applied to sound Synthesised Sound Data (MIDI)