OpenGL

1
OpenGL

• Matt Anderson
• Chris Becker
• George Gensure
• Justin Glaser
• Brian Jenkins

2
The Basics

• Brief history
• Foundation
• Versions Current 1.4, Next 2.0
• Company ownership
• SGI
• Governance
• OpenGL ARB
• OpenGL PCC
• DirectX vs. OpenGL
• COM ( Windows OOP ) vs. C API
• Black Box vs. White Box
• Portability
• Code size and complexity

3
Versions

• 1.1
• Texture bindings
• 1.2
• 3D texturing
• 1.3
• Compressed textures
• Environment mapping
• Multitexturing
• 1.4
• ARB Vertex extension
• Depth and Shadow texturing
• 2.0
• More direct application control of such things as
  texture memory.
• Inclusion of vertex and pixel shading engines

4
Features

• Hardware libraries ( card dependent )
• Software libraries ( card independent )
• Mesa, Windows OpenGL
• Extensions
• wgl, glx, agl, glut, glaux
• GLU

5
API

• Matrices
• The matrix stack
• glPush, glPop, glRotate, glTranslate, glScale
• Defining Vertices
• glBegin, glVertex, glEnd
• Making Color
• glColor

6
Coding example

• glClearColor( 0.0f, 0.0f, 0.0f, 0.0f )
• glClear( GL_COLOR_BUFFER_BIT )
• glShadeModel( GL_SMOOTH )
• glBegin (GL_TRIANGLES)
• glColor3f (1.0, 0.0, 0.0)
• glVertex2f (5.0, 5.0)
• glColor3f (0.0, 1.0, 0.0)
• glVertex2f (25.0, 5.0)
• glColor3f (0.0, 0.0, 1.0)
• glVertex2f (5.0, 25.0)
• glEnd()
• glFlush()

7
Coding example 2

• glClearColor( 0.0f, 0.0f, 0.0f, 0.0f )
• glClear(GL_COLOR_BUFFER_BIT)
• glColor3f(1.0, 1.0, 1.0)
• glLoadIdentity()
• gluLookAt( 0.0, 0.0, 5.0, // camera position
• 0.0, 0.0, 0.0, // look at position
• 0.0, 1.0, 0.0) // up vector
• glScalef(1.0, 2.0, 1.0)
• glutWireCube(1.0)
• glFlush()

8
Textures

• Loading and storing
• RGB, RGBA, BGR
• Mipmapping
• Texture binding
• UV coordinates
• 1D, 2D, 3D
• Linear vs. Nearest

9
Blending

• Alpha channel
• Translucency
• Anti-aliasing
• Gateway to multitexturing

10
Lighting

• Lights
• Ambient, Diffuse, Specular, Shininess
• Materials
• Ambient, Diffuse, Specular, Emissions
• Light Models
• Spotlights
• Local or Infinite
• Attenuation

11
Fog

• Depth queuing
• Linear, Exponential, Exponential2
• Starting and Ending distance
• Density
• Color

12
Face Culling

• Closed surface rendering
• Removes polygons that do not face the camera
• Speeds up rendering
• glEnable( GL_CULL_FACE )
• glCullFace with GL_FRONT, GL_BACK or
  GL_FRONT_AND_BACK

13
Stencil Buffer

• Restricts drawing to certain portions of the
  screen
• Useful for planar reflections and UI

14
NURBS and Evaluator Meshes

• Non-Uniform Rational B-Splines
• Used for modeling smooth and perturbed surfaces

15
Tessellators and Quadrics

• Tessellators are used for breaking up concave
  polygons into convex primitives through winding
  rules
• Quadrics are used for creating geometric objects,
  such as spheres, cylinders and disks
• Both are defined in the GLU

16
Examples