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Introduction to OpenGL

Introduction to OpenGL

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Introduction to OpenGL

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  1. Introduction to OpenGL CGGM Lab. Tan-Chi Ho 2002

  2. Graphics API • A software interface for graphics hardware. • Provide the low-level functions to access graphics hardware directly. • OpenGL / Direct3D CGGM Lab. Tan-Chi Ho 2002

  3. API Hierarchy Application GDI OpenGL Hardware Driver … Display Device CGGM Lab. Tan-Chi Ho 2002

  4. What is OpenGL1/2 • Industry standard. • Hardware independent. • OS independent. CGGM Lab. Tan-Chi Ho 2002

  5. What is OpenGL2/2 • No commands for performing windowing tasks or obtaining user input are included. • No high-level commands for describing models of 3D objects are provided. CGGM Lab. Tan-Chi Ho 2002

  6. What OpenGL provides • Draw with points, lines, and polygons. • Matrix(View) Transformation • Hidden Surface Removal (Z-Buffer) • Light effects • Gouraud Shading • Texture mapping • Pixels operation CGGM Lab. Tan-Chi Ho 2002

  7. The Buffers • A buffer is a memory area in the graphics hardware for some special purposes. • An OpenGL system can manipulate the four buffers: • Color buffers • Depth buffer (Z-Buffer) • Stencil buffer • Accumulation buffer CGGM Lab. Tan-Chi Ho 2002

  8. OpenGL Rendering Pipeline1/2 OpenGL Command Buffer OpenGL API Calls Transformation and Lighting Frame Buffer Rasterization CGGM Lab. Tan-Chi Ho 2002

  9. OpenGL Rendering Pipeline2/2 Per-Vertex Operations and Primitive Assembly Vertex Data Evaluators Per-Fragment Operations Display List Frame Buffer Rasterization Texture Assembly Pixel Data Pixel Operations CGGM Lab. Tan-Chi Ho 2002

  10. OpenGL Libraries • OpenGL Library • The basic library to access the graphics hardware. • GLU • Provide some useful utilities based on the OpenGL library. • GLX / WGL / AGL • OS dependent libraries to bind the OpenGL library with specific window system. • GLX for X-window, WGL for win32, AGL for Apple. CGGM Lab. Tan-Chi Ho 2002

  11. OpenGL Utility Toolkit (GLUT) 1/3 • A window system-independent toolkit to hide the complexities of differing window system APIs. • Use the prefix of glut. (ex: glutDisplayFunc()) • Provide following operations: • Initializing and creating window • Handling window and input events • Drawing basic three-dimensional objects • Running the program CGGM Lab. Tan-Chi Ho 2002

  12. OpenGL Utility Toolkit (GLUT) 2/3 • Where can I get GLUT? • Win32: • http://www.xmission.com/~nate/glut.html • Linux: • http://www.mesa3d.org/ CGGM Lab. Tan-Chi Ho 2002

  13. OpenGL Utility Toolkit (GLUT) 3/3 • On Microsoft Visual C++ 6: • Put glut.h into <MSVC>/include/GL/ • Put glut.lib into <MSVC>/lib/ • Put glut32.dll into <window>/System32/ • On Microsoft Visual C++ .NET: • Put glut.h into <MSVC>/platformSDK/include/GL/ • Put glut.lib into <MSVC>/platformSDK/lib/ • Put glut32.dll into <window>/System32/ CGGM Lab. Tan-Chi Ho 2002

  14. How to Compile1/4 • On Microsoft Visual C++ 6: • Create a new Project with Win32 Console Application • Open Project Settings dialog and add opengl32.lib glu32.lib glut32.lib into Link/Objects/library modules. • Writing your OpenGL code. • Compile it. CGGM Lab. Tan-Chi Ho 2002

  15. How to Compile2/4 • On Microsoft Visual C++ .NET: • 建立Win32專案 • 在應用程式設定,選擇主控台應用程式 • 開啟專案屬性,在連結器/輸入/其他相依性中輸入opengl32.lib glu32.lib glut32.lib。 • Writing your OpenGL code. • Compile it. CGGM Lab. Tan-Chi Ho 2002

  16. How to Compile3/4 CGGM Lab. Tan-Chi Ho 2002

  17. How to Compile4/4 • On UNIX: • Needed libraries: • libGL.so, libGLU.so, libglut.a, libX11.a, libX11.so… • Compile command: • gcc [OpenGL code files] –o [output file] –lglut –lGLU –lGL –lX11 –lm CGGM Lab. Tan-Chi Ho 2002

  18. The Simplest Program1/3 #include <GL/glut.h> void GL_display() { glClearColor(0.0f, 0.0f, 0.0f, 0.0f); glClear(GL_COLOR_BUFFER_BIT); glColor3f(1.0f, 1.0f, 1.0f); glutSolidCube(1.0); glFlush(); } void GL_reshape(GLsizei w, GLsizei h) { glViewport(0, 0, w, h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrtho(-2.0f, 2.0f, -2.0f, 2.0f, -2.0f, 2.0f); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); } CGGM Lab. Tan-Chi Ho 2002

  19. The Simplest Program2/3 void main(void) { glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); glutCreateWindow("Sample"); glutDisplayFunc(GL_display); glutReshapeFunc(GL_reshape); glutMainLoop(); } CGGM Lab. Tan-Chi Ho 2002

  20. The Simplest Program3/3 CGGM Lab. Tan-Chi Ho 2002

  21. Reference1/2 • Official site of OpenGL • http://www.opengl.org • Useful Sites • NeHe’s OpenGL Tutorials • The Developer’s Gallery CGGM Lab. Tan-Chi Ho 2002

  22. Reference2/2 • Further Reading • OpenGL Programming Guide (Red Book) • OpenGL Reference Manual (Blue Book) • OpenGL Super Bible (中文版?) CGGM Lab. Tan-Chi Ho 2002

  23. Any Question? ? CGGM Lab. Tan-Chi Ho 2002