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Chapter 1: Introduction

Chapter 1: Introduction. Admin: Lecture slots : Monday 8-9:45, Tuesday 9:15-11:00. Book : F. Hill, Computer Graphics Using OpenGL (Little Big Bookstore) Evaluation : 3hr closed book, 8 th week (50%) + weekly pracs (50%) Pracs : Windows or Linux, OpenGL. CAREFUL when using 3D Studio Max.

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Chapter 1: Introduction

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  1. Chapter 1: Introduction • Admin: • Lecture slots: Monday 8-9:45, Tuesday 9:15-11:00. • Book: F. Hill, Computer Graphics Using OpenGL (Little Big Bookstore) • Evaluation: 3hr closed book, 8th week (50%) + weekly pracs (50%) • Pracs: Windows or Linux, OpenGL. CAREFUL when using 3D Studio Max. • This is a fun course, but also a LOT of hard work. CS Hons RW778 Graphics

  2. Chapter 1 : Introduction • Week 1: Introduction and OpenGL (Hill, Ch. 1,2). • Week 2: Windows and viewports; vector tools (Hill, Ch. 3,4). • Week 3: Vector tools (continued) (Hill, Ch. 4). • Week 4: Transformations on objects (Hill, Ch. 5). • Week 5: Polygonal meshes (Hill, Ch. 6). • Week 6: 3D viewing (Hill, Ch. 7). • Week 7: Lighting and face realism (Hill, Ch. 8). • Week 8: Exam Wednesday 09:00 CS Hons RW778 Graphics

  3. Chapter 1: Introduction • 1.1 What is computer graphics (CG)? • Simply pictures • Tools • Field of study • 1.2 Where is CG used? • Art, entertainment, publishing • Image processing • Process monitoring, simulations, CAD • Scientific visualization CS Hons RW778 Graphics

  4. Chapter 1: Introduction • 1.3 Elements of pictures created in CG • Output primitives and attributes: • Polylines • Text • Filled regions • Raster images • 1.3.1 Polylines • Connected sequence of straight lines CS Hons RW778 Graphics

  5. Chapter 1: Introduction • Edge, vertex, polygon, simple polygon • Attributes: color, thickness, dashing, endpoint blending CS Hons RW778 Graphics

  6. Chapter 1: Introduction • 1.3.2 Text • Font, color, size, spacing, orientation • Tilting (graphs) • 1.3.3 Filled regions • Filled shape – boundary (polygon) • Filling used for shadow effects CS Hons RW778 Graphics

  7. Chapter 1: Introduction • 1.3.4 Raster image • Consists of cells (called pixels) with color value • Stored as array of numerical values • Bitmap : 0-1 • Created as hand-designed, or computed, or scanned. • Computed: straight lines – “jaggies” • Easy manipulation (filters, cleanup) CS Hons RW778 Graphics

  8. Chapter 1: Introduction • 1.3.5 Shades of gray and color in raster images • Pixel depth : n bits => 2n values (at least 256) • Smaller pixel depth => loss in quality. Banding. • Color: RGB • Color depth => sum of bits for each color • High quality (true color) : 24 bits (eye perception) • 1.4 Graphics Display Devices • 1.4.1 Line drawing (plotters): cross-hatching CS Hons RW778 Graphics

  9. Chapter 1: Introduction • 1.4.2 Raster displays (video monitor, flat-panel displays, printers) • Display surface (X,Y) • Frame buffer : memory to hold display pixels, with scan controller. CS Hons RW778 Graphics

  10. Chapter 1: Introduction • Some hardware (video monitor) requires “refresh” : entire frame buffer scanned out to display many times per second. CS Hons RW778 Graphics

  11. Chapter 1: Introduction • Video monitors : • CRT • Digital-to-analog converters (DACs) • Refresh 60x per second to prevent flicker. • Scanning per line CS Hons RW778 Graphics

  12. Chapter 1: Introduction • 1.4.3 Indexed Color and the LUT • Programmable association between pixel value and color • Bits in frame buffer acts as index into LUT. • Palette: set of possible colors AT ONE TIME. • 1.4.4 Other raster display devices: flat-panel, LCD, active matrix panels, plasma panel • 1.4.5 Hard-copy raster devices: film recorder, laser printer, inkjet plotter. PostScript. • 1.5 Graphics input primitives and devices • Selfstudy. CS Hons RW778 Graphics

  13. Chapter 2: Drawing in OpenGL • 2.1 Getting started • Environment: window, coordinate system, elementary drawing routines • 2.1.1 Device-independence and OpenGL • Libraries • 2.1.2 Windows-based Programming • Event-driven, event queue and callbacks • System-dependent (glut) • Example: Fig. 2.2 CS Hons RW778 Graphics

  14. Chapter 2: Drawing in OpenGL #include <gl/Gl.h> #include <gl/glut.h> //<<<<<<<<<<<<<<<<<<<<<<<< main >>>>>>>>>>>>>>>>>>>>>> void main(int argc, char** argv) { // initialize // create screen window glutDisplayFunc (myDisplay); glutMouseFunc (myMouse); glutKeyboardFunc (myKeyboard); glutMainLoop(); // go into a perpetual loop } CS Hons RW778 Graphics

  15. Chapter 2: Drawing in OpenGL • 2.1.3 Opening a window for drawing (framework) #include <gl/Gl.h> #include <gl/glut.h> //<<<<<<<<<<<<<<<<<<<<<<<< main >>>>>>>>>>>>>>>>>>>>>> void main(int argc, char** argv) { glutInit(&argc, argv); // initialize the toolkit glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); // set display mode glutInitWindowSize(640,480); // set window size glutInitWindowPosition(100, 150); // set window position on screen glutCreateWindow("my first attempt"); // open the screen window glutDisplayFunc(myDisplay); // register redraw function myInit(); glutMainLoop(); // go into a perpetual loop } CS Hons RW778 Graphics

  16. Chapter 2: Drawing in OpenGL • 2.2 Drawing basic graphics primitives • Establish coordinate system • Line drawing primitives : glBegin, glEnd, vertices • Example: glBegin (GL_POINTS); glVertex2i(100,50); glVertex2i(100,130); glVertex2i(150,130); glEnd(); • OpenGL commands: glVertex2i (…) CS Hons RW778 Graphics

  17. Chapter 2: Drawing in OpenGL • OpenGL data types : GLint, GLfloat • OpenGL state: current state variables. • glColor3f (red, green, blue) • glClear (GL_COLOR_BUFFER_BIT) • Establish coordinate system • Matrices and transformations (ch. 3) • Fig. 2.10: A complete OpenGL program • Note glFlush(); CS Hons RW778 Graphics

  18. Chapter 2: Drawing in OpenGL • 2.2.1 Drawing dot constellations • The Big Dipper • The Sierpinski Gasket • Simple dot plots (note scaling and shifting, which are affine transformations) • 2.3 Line Drawings glBegin (GL_LINES); glVertex2i(40, 100); glVertex2i(202, 96); glEnd(); CS Hons RW778 Graphics

  19. Chapter 2: Drawing in OpenGL • More than 2 vertices : paired • 2.3.1 Drawing polylines and polygons • Polyline: collection of joined line segments, specified by ordered list of points. • OpenGL: GL_LINE_STRIP (open line segment) • GL_LINE_LOOP (closed line segment – not fillable area – GL_POLYGON) • Examples: line graphs, polylines from file, parameterizing figures, polyline drawer CS Hons RW778 Graphics

  20. Chapter 2: Drawing in OpenGL • 2.3.2 Line drawing with moveto() and lineto() • Current position • 2.3.3 Drawing aligned rectangles • glRecti(x1,y1,x2,y2) • 2.3.4 Aspect ratio of aligned rectangle • width/height • NB! Work through all practice exercises on pp. 60—61. CS Hons RW778 Graphics

  21. Chapter 2: Drawing in OpenGL • 2.3.5 Filling polygons • Must be convex! • 2.3.6 Other graphics primitives: • GL_TRIANGLES,GL_QUADS,GL_TRIANGLE_STRIP • GL_TRIANGLE_FAN,GL_QUAD_STRIP CS Hons RW778 Graphics

  22. Chapter 2: Drawing in OpenGL • 2.4 Simple mouse and keyboard interaction • glut callbacks on events: glutMouseFunc, glutMotionFunc, glutKeyboardFunc • 2.4.1 Mouse interaction : selfstudy • 2.4.2 Keyboard interaction : selfstudy • 2.6 Case studies: SELFSTUDY CS Hons RW778 Graphics

  23. Chapter 2: Drawing in OpenGL • Programming Task 1 : Implement Case Study 2.5 (Polyline Stippling), p. 75, in Hill. • Familiarize yourself with OpenGL, Linux (or Windows) and C/C++. • The usual rules for programming projects hold: • No extensions (demo Monday 08:00) • No copying/cheating • Accompanying report to be handed in at demo CS Hons RW778 Graphics

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