1. OpenGL Help Session CS248 Fall 2008 Derek Chan

2. OpenGL needs a windowing system OpenGL by itself does not talk to the windowing system/manager by itself. Need a toolkit to tell the windowing system that we need an OpenGL window. Examples: GLUT/ GLUI (used in Project 2)‏ SDL (more features: sound, image file loaders)‏ wxWidgets, Qt (full fledged widget toolkits, probably overkill for a game)‏

3. OpenGL needs a windowing system What does the windowing toolkit handle? Opening a window in the OS Window resizing Mouse/ keyboard presses Mouse position/movement What does OpenGL do? - draw

4. Drawing glBegin(): GL_POINTS GL_LINES GL_TRIANGLES Etc.

5. Drawing glBegin(GL_LINES); glColor3f(r,g,b); glNormal3f(x,y,z); glTexCoord2d(u,v); glVertex3f(x,y,z); … glEnd();

6. OpenGL function suffixes OpenGL functions that take different types of arguments while providing the same functionality will often have a suffix to denote which type of function they are: glVertex2i - input is 2 integers glVertex3fv - input is 3 floats in an array glVertex3f - input is 3 floats

7. OpenGL Camera glFrustrum gluPerspective glOrtho gluOrtho2d glViewport gluLookAt

8. OpenGL glEnable( )‏ glDisable( )‏ GL_DEPTH_TEST GL_BLEND GL_LIGHTING GL_LIGHT1

9. OpenGL Find simple tutorials online OpenGL does many things which you might not know about Display Lists (glGenLists, glCallList)‏

10. OpenGL extensions Extensions to the OpenGL base system often have their own suffixes. For example: glCreateProgramObjectARB (to create a shader program using an ARB extension)‏ Use GLEW (OpenGL Extension Wrangler) for easy access to extensions.

11. Basic OpenGL Game Flowchart 1. Load up an OpenGL window using a toolkit to talk to the windowing system Set up projection matrices, shading properties, etc. Load textures, etc. Event loop: Check for any events or user input and process them Redraw the OpenGL scene as necessary Wait a small amount of time.

12. General Programming Advice 1. have a math library 2. use object oriented programming 3. use c++ stl classes (or equivalent)‏

13. Example Pitfalls Depth Testing vs blending (transperancies)‏ Texture dimensions – power of 2 (fixed in more recent implementations of OpenGL)‏ Projection matrix should only be used for camera position, etc. It has a shorter stack than the Model- View matrix.