CSC Graphics Programming. Budditha Hettige Department of Statistics and Computer Science

Transcription

1 CSC Graphics Programming Department of Statistics and Computer Science

2 Graphics Programming 2

3 Common Uses for Computer Graphics Applications for real-time 3D graphics range from interactive games and simulations to data visualization for scientific, medical, or business uses Military flight simulators Computer-aided design (CAD) Architectural or civil planning Scientific visualization Entertainment 3

4 Movies 4

5 Games 5

6 Simulation 6

7 CAD-CAM & Design 7

8 Architecture 8

9 Virtual Reality 9

10 Visualization 10

11 Medical Imaging 11

12 Graphics System User Program Graphics System IO Devices Graphics API 12

13 Graphics Designing 13

14 Graphics: Conceptual Model Real Light Real Object Human Eye Synthetic Light Source Synthetic Camera Real Object Synthetic Model Display Device Human Eye Graphics Budditha System Hettige 14

15 OpenGL Standard specification defining a cross-language, crossplatform API Is not a programming language Writing applications that produce 2D and 3D computer graphics A software interface to graphics hardware Designed and optimized for the display and manipulation of 3D graphics Developed by Silicon Graphics Inc. (SGI) in

16 OpenGL-Graphics rendering API Rendering API High-quality color images composed of geometric and image primitives Window system independent Operating system independent OpenGL Pipeline 16

17 OpenGL Architecture Polynomial Evaluator Per Vertex Operations & Primitive Assembly CPU Display List Rasterization Per Fragment Operations Frame Buffer Pixel Operations Texture Memory 17

18 Software & Hardware Interfaces Software Interface Hardware Interface 18

19 OpenGL and Related APIs application program OpenGL Motif widget or similar GLX, AGL or WGL GLUT GLU X, Win32, Mac O/S GL software and/or hardware 19

20 Related APIs AGL, GLX, WGL glue between OpenGL and windowing systems GLU (OpenGL Utility Library) part of OpenGL NURBS, tessellators, quadric shapes, etc. GLUT (OpenGL Utility Toolkit) portable windowing API not officially part of OpenGL Initial header inclusions (for Windows) #include<windows.h> #include<gl/gl.h> #include<gl/glu.h> #include <GL/glut.h> 20

21 Function-Naming Conventions All OpenGL functions take the following format <Library prefix><root command><optional argument count><optional argument type> 21

22 OpenGL data types 22

23 2D Coordinates 23

24 Coordinate Clipping 24

25 Viewports Mapping Drawing Coordinates to Window Coordinates viewport defined as twice the size of the clipping area 25

26 Viewports viewport that matches the clipping area 26

27 OpenGL 3-D coordinates Right-handed system From point of view of camera looking out into scene: +X right, -X left +Y up, -Y down +Z behind camera, -Z in front Positive rotations are counterclockwise around axis of rotation 27

28 OpenGL Geometric Primitives Primitives are one- or two-dimensional entities or surfaces such as points, lines, and polygons GL_LINE_STRIP GL_LINE_LOOP GL_POINTS GL_LINES GL_POLYGON GL_TRIANGLES GL_TRIANGLE_STRIP GL_TRIANGLE_FAN GL_QUADS GL_QUAD_STRIP 28

29 The Vertex A Position in Space Each corner of the any primitive is called a vertex. Ex: three-dimensional cube consists of six two dimensional squares, each placed on a separate face 29

30 Projections: Getting 3D to 2D Orthographic Projections Perspective Projections 30

31 RGB Color Space G Cyan (0,1,1) Green (1,0,0) White (1,1,1) Yellow (1,1,0) Image: Pixel maps to color B Blue (0,0,1) Blk Magenta (1,0,1) Red (1,0,0) R 31

32 Common Composite Colors 32