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WHAT IS OPENGL?
“a software interface to graphics hardware.”
Low- level graphics API
Fast and portable 3D graphics library
NOTE: OpenGL is ONLY a graphics library
3 OPENGL LIBRARIES
OpenGL (GL) – used in modeling an object via a set of geometric primitives such as point, line and polygon.
OpenGL Utility Library (GLU)- important utilities (such as setting camera view and projection) and more building models (such as quadric surfaces and polygon tessellation).
OpenGL Utilities Toolkit (GLUT) – used for creating a window, handling key and mouse inputs. It also provides more building models (such as sphere and torus).
HOW TO INCLUDE OPENGL LIBRARY
#include <gl/gl.h>
#include <gl/glu.h>
#include <gl/glut.h>
#include <gl/freeglut.h>
Silicon Graphics Inc. (SGI) used “IRIS GL”, a 3D programming API in their high-end IRIS graphics workstations.
When SGI tried porting IRIS GL to other hardware platforms problems occurred :(
OpenGL is the result of SGI’s efforts to improve IRIS GL’s portability (came out in 1992).
HISTORY
OpenGL 1.x - fixed function
OpenGL 2.x - early programmable
OpenGL 3.x/4.x - modern programmable,Core profile and deprecation
OpenGL ES 1.x - mobile fixed function
OpenGL ES 2.x - mobile programmable
FIVE GENERATIONS OF OPENGL
HOW OPENGL WORKS
OpenGL is a procedural rather than a descriptive graphics language.
Instead of describing the scene and how it should appear, the programmer actually describes the steps necessary to achieve a certain appearance or effect.
DESCRIPTIVE
PROCEDURAL
Orange cube rotated at 90°
1. Rotate at 90°2. Orange3. Cube4. Vertex 1 at [-1,1,1]5. Vertex 2 at [1,1,1]6. …. 7. ….
POPULAR OPENGL-BASED PROGRAMSAdobe After Effects
Autodesk Maya
Autodesk AutoCAD
Google Earth
Counter-Strike
Minecraft
Left 4 Dead 2
Portal2
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