1. Introduction : What is OpenGL
Software interface to graphics hardware
Hardware-independent interface
OpenGL's main purpose is to render two- and three-dimensional objects into a frame buffer.

2. Fundamentals Primitives and Commands
defined by a group of one or more vertices
Commands are always processed in the order in which they are received
Procedural versus Descriptive
Execution Model
client-servermodel for interpretation of OpenGL commands

3. Basic OpenGL Operation
High-level block diagram of how OpenGL processes data

4. Getting started with OpenGL
Initialisation
Setting up the window for rendering
Set up the correct window style and class attribute : WS_CLIPSIBLINGS and WS_CLIPCHILDREN Should have CS_OWNDC instead of CS_PARENTDC
Set up a pixel format
Create a device context
Creating a rendering context.

5. Pixel Format
Description of the actual format given to a particular window
Some of the properties that you want some control over
Single or double buffering
Drawing to a window and/or bitmap
Supporting GDI and/or OpenGL calls
RGBA or color-indexed
Color depth (bits/pixel)
z-axis depth

6. Getting started with OpenGL Contd.
Tell OpenGL about the window you're rendering to and how you want your scene to be viewed
Responding to the WM_SIZE message.
Responding to the WM_PAINT message.
Responding to the WM_ERASEBACKGROUND message.
Responding to the WM_PALETTECHANGED, WM_QUERYNEWPALETTE, and WM_ACTIVATE messages (if you use a color-index pixel format).
Deleting the RC and DC when your program finishes.

7. Initialisation

8. Simple example using OpenGL
Add OpenGL32.lib GLu32.lib and GLaux.lib
Include the header files
#include <windows.h> // Header File For Windows
#include <gl\gl.h> // Header File For The OpenGL32 Library
#include <gl\glu.h> // Header File For The GLu32 Library
#include <gl\glaux.h> // Header File For The GLaux Library
InitGL
glShadeModel(GL_SMOOTH);
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
ReSizeGLScene(GLsizei width, GLsizei height)
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
glMatrixMode(GL_MODELVIEW);

9. Simple example using OpenGL : Contd.
DrawGLScene(GLvoid)
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glTranslatef(-1.5f,0.0f,-6.0f);
glBegin(GL_TRIANGLES); glVertex3f( 0.0f, 1.0f, 0.0f); glVertex3f(-1.0f,-1.0f, 0.0f); glVertex3f( 1.0f,-1.0f, 0.0f); glEnd();
CreateGLWindow()
CreateWindow()
Initialise Pixel Format PIXELFORMATDESCRIPTOR pfd
ChoosePixelFormat(hDC,&pfd)
SetPixelFormat(hDC,PixelFormat,&pfd)
wglCreateContext(hDC)
wglMakeCurrent(hDC,hRC)
call ReSizeGLScene(width, height);
call InitGL()

10. Frame Buffers Contain different amounts of data per pixel
Bitplane : A buffer that stores a single bit of information about pixels
Color buffer
holds the color information You can use GL_STEREO or GL_DOUBLEBUFFER
Depth buffer
stores a depth value for each pixel
Stencil buffer
to restrict drawing to certain portions of the screen
Accumulation buffer
holds RGBA color data
accumulating a series of images into a final, composite image

11. Colors
each pixel emits different amounts of red, green, and blue light
can be stored either in RGBA mode or color index mode
API used
glColor3f (1.0, 0.0, 0.0);

12. Rotation Three major axes and therefore three rotations API used
glRotatef(Angle,Xvector,Yvector,Zvector)

13. Drawing Solid Objects
glVertex3f( 0.0f, 1.0f, 0.0f); // Top Of Triangle (Front) glVertex3f(-1.0f,-1.0f, 1.0f); // Left Of Triangle (Front) glVertex3f( 1.0f,-1.0f, 1.0f); // Right Of Triangle (Front)
Display lists
group of OpenGL commands that have been stored for later execution
improve performance
API's used
gluint glGenLists()
glNewList(listname, GL_COMPILE)
glEndList()

14. Texture Mapping Textures are simply rectangular arrays of data
Allows you to glue an image to a polygon
Texture mapping ensures that all the right things happen as the polygon is transformed and rendered
Filtering
Process of averaging or interpolating texels
provide different trade-offs between speed and image quality
API's used
glTexParameteri() for GL_TEXTURE_MIN_FILTER and GL_TEXTURE_MAG_FILTER
Parameter : GL_NEAREST or GL_LINEAR or MIPMAP

15. Blending
Tells how to specify a blending function that combines color values from a source and a destination
Occurs after your scene has been rasterized and converted to fragments, but just before the final pixels are drawn in the framebuffer
Basic Alpha Blending
result = ALPHA * srcPixel + ( 1 - ALPHA ) * destPixel
API's
glColor4f(1.0f,1.0f,1.0f,0.5f);
glBlendFunc(GL_SRC_ALPHA,GL_ONE);

16. 2D Texture Font
use just one texture to display any of 256 different characters on the screen.
average character is 16 pixels wide and roughly 16 pixels tall.
Take your standard 256x256 texture it's easy to see that you can fit 16 letters across, and you can have a total of 16 rows up and down.
glPushMatrix()
glPopMatrix();

17. Quadratics
used to create complex objects such as spheres, discs, cylinders and cones.
GluNewQuadric()
gluQuadricNormals(quadratic, GLU_SMOOTH);
glTranslatef(0.0f,0.0f,-1.5f); // Center The Cylinder
gluCylinder(quadratic,1.0f,1.0f,3.0f,32,32); // Draw Our Cylinder
Tessellation
to display of concave polygons, polygons containing hole, or polygons with intersecting edges

18. Masking two step process:
place a black and white image of the texture on top of the scene
switch blending modes, and map the texture on top of the black cut out.

19. Clipping & Reflections
Requires stencil buffer
Steps :
gluSphere()
glBindTexture(GL_TEXTURE_2D, texture[2]);
glColor4f(1.0f, 1.0f, 1.0f, 0.4f);
glEnable(GL_BLEND); // Enable Blending
glBlendFunc(GL_SRC_ALPHA, GL_ONE);
glEnable(GL_TEXTURE_GEN_S); //enable Sphere Mapping
glEnable(GL_TEXTURE_GEN_T); // Enable Sphere Mapping
gluSphere(q, 0.35f, 32, 16);
clearing the buffers
define clipping plane eqaution : used for clipping the reflected image.

20. Clipping & Reflections : Contd
set the color mask to white
glColorMask(0,0,0,0);
enable stencil testing
glEnable(GL_STENCIL_TEST);
glStencilFunc(GL_ALWAYS, 1, 1);
glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
Draw the floor
Change the color mask to opaque
enable the clipping plane
draw the reflected image

21. Shadows Extensively uses the stensil buffer
A shaded region is a region in a scene that cannot be "seen" by a light source.
INFINITY : how far to extend the shadow volume polygons
Data reuired for casting a shadow :
array of vertices
vertex normals : to calculate orientation of the face
plane equation
indices into the array of faces in the object : to define edges

22. Limitations
Printing
OpenGL and GDI graphics cannot be mixed in a double-buffered window
There are no per-window hardware color palettes.
There is no direct support for the Clipboard, dynamic data exchange (DDE), or OLE
There is no support for the following pixel format features: stereoscopic images, alpha bitplanes, and auxiliary buffers