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CD2012 Principles of Interactive Graphics Lecture 08

CD2012 Principles of Interactive Graphics Lecture 08. Objects and Interactions Abir Hussain www.cms.livjm.ac.uk/cmsahus1. Previous Lecture. Creating texture within program Using texture Texture co-ordinates. Recall-Texture co-ordinates.

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CD2012 Principles of Interactive Graphics Lecture 08

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  1. CD2012Principles of Interactive GraphicsLecture 08 Objects and Interactions Abir Hussain www.cms.livjm.ac.uk/cmsahus1

  2. Previous Lecture • Creating texture within program • Using texture • Texture co-ordinates CD2012-08

  3. Recall-Texture co-ordinates • The coordinates of textures are named s along the X axis and t along the Y axis • The values of S and T range between 0.0 and 1.0 • We can use values between 0.0 and 1.0 to select part of the imaged to be mapped, or • We can use values greater than 1.0 to map multiple copies of the single texture across a polygon • Texture coordinates are set for each vertex of the target polygon with glTexCoord2f() CD2012-08

  4. Recall-Texture co-ordinates CD2012-08

  5. Today’s lecture and Lab CD2012-08

  6. Introduction • In CY2001 you will have come across concepts such as: • Defining Classes and Objects • Encapsulation (private variables and functions for classes) • Polymorphism - functions with the same name but different parameters • Moving from OO design to OO Programming CD2012-08

  7. Introduction • Abstraction (to different levels) is the main technique of problem solving in Computer Science. • OOD works by abstracting out the essential classes of objects in a problem. • identifying their attributes and their functionality • OOD and OOP help control the complexity of larger systems development. • In your own programs you will have seen the Display() function grow in size with the complexity of the graphical scene. • How could you have use OOD and OOP to control and manage this growth? CD2012-08

  8. OO Graphical user Interfaces • Smalltalk 80 was the first complete object-oriented programming environment. • http://www.cincom.com/scripts/smalltalk.dll//downloads/index.ssp • Everything in Smalltalk-80 is an object, from integers upwards. CD2012-08

  9. OO Graphical user Interfaces • The designers chose to split an application up into three part • The View - the graphical part • The Controller - the input handling part • The Model - the logical part of the application (text handling, database handling or whatever) • Objects in the Controller (e.g. a menu handler) send messages to the Model to do some calculation, which then sends a message to update the View. CD2012-08

  10. How did you design your car park?

  11. Designing your Own graphical Object • OpenGL is designed around the idea of sending commands down a graphical pipeline. • This maybe a good way of developing graphically intense programs such as games. • While this reflects the underlying hardware it is not always the best way to program all graphical applications. CD2012-08

  12. Designing your Own graphical Object • In your coursework you may have split up the display() function to call other functions to draw the parts of the scene • For example, a car() function which could draw a car in various locations CD2012-08

  13. Designing your Own graphical Object • The car() function could be extended to further parameters such as: • Colour of the car • Size of the car • Model of the car • The doors and the windows CD2012-08

  14. Designing your Own graphical Object • We could take advantage of OOD and design a car Class comprising: • Private attribute of the attributes listed above • An attribute for the current_location value • Constructors to create a new Car object • A draw function (hiding the OpenGL implementation) • An update function to change current_position and redraw the car CD2012-08

  15. Designing your Own graphical Object • The rest of the program would then only communicate with the car via • car.setCurrentPosition(int x, int y); • Think for a moment of what other objects in your scene you could create classes for • What would be their attributes? • What methods would be needed? • What attributes would be exposed to the rest of the program to update your object? CD2012-08

  16. Coursework 2 • In the second coursework, you are required to built a 3D office. • Use a pop up menu, keyboard interactions and buttons to allow the office: • To rotate about the three axes. • To scale the office in x and y-axes. • To change the colour of the various parts of the office from a choice of three colours. Extra mark can be gained by performing the three types of interactions!! CD2012-08

  17. Today’s Lab • Demonstration of coursework 1 • You are required to submit a copy of your program (even if it is not completed) CD2012-08

  18. Summary • Object Oriented programming and design • Object oriented graphical user interface • Designing your own graphical object • Coursework 2 • Demonstrating coursework 1 CD2012-08

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