1 A first OpenGL program Brian Farrimond Robina Hetherington

2 Ex01 Build and run Ex01

3 Program structure Three function program

4 main

5 Always present Uses RGB colours (Red, Green, Blue)

6 main Sets up the scene window

7 Window exercises Double the size of the window height and width Make the window start at the top left corner of the screen Change the window title to “2D OpenGL”

8 main Set up the graphical characteristics of the new window

9 init Set the background colour: red green blue alpha (transparency) Min value: 0.0 Max value: 1.0 Exercise: Set the background colour to red

10 init Set projection to be orthographic

11 Projections Orthographic projection shows no perspective

12 Orthographic projection glOrtho(left, right, bottom, top, near, far)

13 main

14 main Name of the function that will draw the scene

15 display

16 display Clear the window using the background colour

17 display glColor3f(red, green, blue) Min value: 0.0 Max value: 1.0 Exercise: Make the rectangle yellow

18 display Draw the rectangle (polygon with four vertices)

19 glVertex(x, y, z)

20 glVertex(x, y, z)

21 glVertex(x, y, z)

22 glVertex(x, y, z)

23 glVertex(x, y, z)

24 glVertex(x, y, z) Vertices are in anticlockwise order

25 g lOrtho(left, right, bottom, top, near, far); glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);

26 g lOrtho(left, right, bottom, top, near, far); glOrtho(-0.5, 1.0, 0.0, 1.5, -1.0, 1.0);

27 The new projection

28 main How we manage animation and interaction

29 OpenGL drawing primitives

30 OpenGL drawing primitives

31 OpenGL drawing primitives

32 OpenGL drawing primitives

33 OpenGL drawing primitives

34 OpenGL drawing primitives