VG101 RECITATION 5

1. VG101RECITATION 5 By TAs

2. CONTENTS • How to read Vg101Class.h • Samples about graphics • About assignment 5 • Array

3. HOW TO READ VG101CLASS.H • This file defines the following classes: • ConsoleT • GwindowsT: represent the graphics window • GObjectT: base class for all geometric classes • LineT • TriangleT • RectangleT • ArcT: a circle is an arc with an angle of 360 degrees

4. HOW TO READ VG101CLASS.H • RandomT: random numbers and colors • PointT: represent a point using (x, y) • PenT: record the current location and color of the pen • MouseT: detect the click event of the mouse, get mouse current location • TextT: set text color, style, font… when printing a message to the graphics window (not console window)

5. HOW TO READ VG101CLASS.H • Let’s see what’s the general structure of a class definition

6. Base class Data members Private member constructor class RectangleT : public GObjectT { PointT llp, urp; void drawRect (); public: RectangleT (const double x0 = 0, const double y0 = 0, const double x1 = 0, const double y1 = 0, const string clr = "Blue", const double fill = 0); RectangleT (const PointT &p0, const PointT &p1, const string clr = "Blue", const double fill = 0); const PointT &getLocation () {return llp;} double getWidth () const; double getHeight () const; double getArea () const; void setLocation (const double x, const double y); void setLocation (const PointT p); void setWidth (const double w); void setHeight (const double h); void draw (); void draw (const string clr, const double density = 0); }; Public member Get & Set Function members

7. HOW TO READ VG101CLASS.H • About constructors RectangleT (const double x0 = 0, const double y0 = 0, const double x1 = 0, const double y1 = 0, const string clr = "Blue", const double fill = 0); RectangleT (const PointT &p0, const PointT &p1, const string clr = "Blue", const double fill = 0); • Note: • 1. No return type, function name is just its class name. • 2. You should declare an object using one of its constructors:

8. HOW TO READ VG101CLASS.H • If the constructor gives the default value of a parameter, then you don’t need to give that parameter. use RectangleT myRec(); // default position, color, fill or RectangleT myRec(1, 1, 2, 3); // default color, fill or RectangleT myRec(1, 1, 2, 3, “red”, 0.5); // p1, p2 are two known PointT object or RectangleT myRec(p1, p2); // default color, fill or RectangleT myRec(p1, p2, “green”, 0.8);

9. HOW TO READ VG101CLASS.H • What are useful to us • Get and Set functions double getWidth () const; void setWidth (const double w); • Other public functions void draw (); void draw (const string clr, const double density = 0); // overloaded function Note: 1. You can’t access private/protected data or use private/protected functions directly. 2. The get & set functions offer you access to some private data. 3. Read function comment carefully.

10. Samples about graphics • Draw a line from (2,1) to (5,3) in red

11. SAMPLES ABOUT GRAPHICS • Draw an empty triangle specified by three points (1,1), (3, 1), (2.3, 3) in green

12. SAMPLES ABOUT GRAPHICS • Draw a filled triangle specified by three points (1,1), (3, 1), (2.3, 3) in green with density of 0.4

13. SAMPLES ABOUT GRAPHICS • Draw an empty rectangle whose lower left point is (0.5, 0.5) and upper right point is (1.5, 1.2) in yellow

14. SAMPLES ABOUT GRAPHICS • Draw a filled rectangle whose lower left point is (0.5, 0.5) and upper right point is (1.5, 1.2) in yellow with density of 0.8

15. SAMPLES ABOUT GRAPHICS • Draw an arc start from0 degree and sweep 270 degree with radius 0.6 in purple, centered at (0.6, 0.6)

16. SAMPLES ABOUT GRAPHICS • Draw an empty circle with radius 0.6 in purple, centered at (0.6, 0.6)

17. SAMPLES ABOUT GRAPHICS • Draw a filled circle with radius 0.6 in purple, centered at (0.6, 0.6) with density of 0.9

18. ABOUT ASSIGNMENT 5 • Where’s Tom • Understand the pseudo code for function takeTomHome () • Every step is a line with constant length (step size) in a random direction • Check before taking the step if Tom is going out of the universe (the do-while loop in pseudo code) • Check after taking the step if Tom is already at home

19. ABOUT ASSIGNMENT 5 • Bouncing ball • Check before taking the step if the ball is going to hit the wall • When hitting the wall, adjust the location of the ball so that it just touch the wall (on the line of its original direction) • Change color when change direction • Don’t use magic numbers • Give a good name for your variables

20. Array • An array is an ordered collection of data values of the sametype • Passing an array into a function • void initArray(int array[], int n); • void printArray(int array[], int n); • Usually, n is the array length

21. ARRAY • A sample on passing an array into a function #include <Vg101Class.h> #include <cmath> using namespace std; void initArray ( int intArray[], int n); void printArray ( int intArray[], int n); void main() { int intArray[4]; initArray ( intArray, 4); printArray ( intArray, 4); }

22. ARRAY • A sample on passing an array into a function void initArray(int intArray[], int n) { ConsoleT c; for ( int i = 0 ; i < n ; i++) { c.printLine ( "Enter a integer value for the ", i+1, " th element: "); intArray[i] = c.readInt ("");; } c.printLine ( endl ); }

23. ARRAY • A sample on passing an array into a function void printArray(int intArray[], int n) { ConsoleT c; for ( int i = 0 ; i < n ; i++) { c.printLine ( "The ", i+1, " th element is ", intArray[i], endl ); } }

24. ARRAY • Here is the program’s output