1. OpenGL and Related Libraries
DEMO 1
DEMO 2
WHAT IS OpenGL?
The OpenGL graphics system is an application programming interface (API) to graphics hardware
@ 2017 by Jim X. Chen:
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2. @ 2017 by Jim X. Chen: jchen@cs.gmu.edu
OpenGL-Related Libraries
The OpenGL Utility Library (GLU) contains
several routines that use OpenGL commands.
It is considered part of your OpenGL.
The OpenGL Extension to the X Window
System (GLX) provides a means of creating an
OpenGL context and associating it with a
drawable window on a machine that uses the X.
OpenGL Auxiliary Library (AUX) or Utility
Toolkit (GLUT)
to make programming examples simpler.
Works for X, Win, Apple, etc.
WGL for Windows; AGL for Apple; PGL for OS/2
JOGL – Java OpenGL API
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OpenGL and DirectX libraries
Theoretically, OpenGL and DirectX (Direct3D) are the same
OpenGL and Direct3D are mature graphics library
OpenGL is easier to learn and use, and is integrated in most modern graphics textbooks
DirectX is much more popular in PC game industry in the past
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JOGL – Java for OpenGL
JOGL implements Java bindings for OpenGL.
Provides platform for 3D graphics applications in Java
JOGL provides full access to OpenGL functions and integrates with the AWT or Swing widget sets.
Part of a suite of open-source technologies initiated by the Game Technology Group at Sun Microsystems.
JOGL1_0_Frame
* JOGL initial set up:
* Open a frame with a background color
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Shaders
Earlier GPU programming are through separate libraries: Cg, HLSL, etc.
OpenGL 4.x includes GLSL as a standard: shader programming that runs on GPU
Cg library faced out 2013
Old CPU graphics pipeline faced out
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6. The rendering pipeline
Vertex shader: parallel vertex processing
Fragment shader: parallel fragment processing
JOGL1_0_Point
Draw a point with vertex and fragment shaders
JOGL1_1_PointVFfiles
vertex and fragment shader programs are stored in corresponding files
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Animation
Motion in a movie was achieved by projecting a sequence of pictures at 24 frames per second on the screen
60 f/s is smoother than 30, and 120 is marginally better than 60. Refresh rates faster than 120 make no difference.
Double-buffering
The frontbuffer is displayed while the backbuffer is drawn.
When the drawing of a frame is complete, the two buffers are swapped.
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JOGL’s Animator
JOGL1_2_Animate
* Animate a point
* Animator starts a thread that calls display() repetitively
* Uniform sends a variable value from JOGL main program to the shader program
Technical details are covered in the program
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9. For Drawing an Object Just Once
JOGL1_2_Animate
comment out clearing the background: a shimmy line (alternating points in two buffers)
Treat double-buffer as a single-buffer
setting glDrawBuffer() to GL_FRONT with a glFlush() call.
To switch back to double-buffered, you need to set glDrawBuffer() to GL_BACK.
You can just choose to draw into both buffers:
glDrawBuffer(GL_FRONT_AND_BACK);
@ 2017 by Jim X. Chen:

10. @ 2017 by Jim X. Chen: jchen@cs.gmu.edu
Some old Examples Coded In OpenGL
DEMO 1
DEMO 3
DEMO 5
DEMO 7
DEMO 2
DEMO 4
DEMO 6
DEMO 8
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Vector Operations
Vector: a and b
a=(a0, a1, a2); b=(b0, b1, b2);
It gives a length and a direction
Length: |a| = sqrt(a0*a0 + a1*a1 + a2*a2)
Direction: a/|a| = (a0 /|a| , a1 /|a| , a2 /|a| )
// normalize a vector to unit vector
public void normalize(double a[]) {
double d = Math.sqrt(a[0]*a[0] + a[1]*a[1]+ a[2]*a[2]);
if (d == 0) {System.err.println("0 length vector: normalize()."); return;}
a[0] /= d; a[1] /= d; a[2] /= d; }
GLSL: normalize(vec3) or normalize(vec4)
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12. Vector Operations – Cont.
Addition/Subtraction
a+b = (a0+b0, a1+b1, a2+b2);
GLSL: vec3 ± vec3
Dot Product (easy for finding cos)
ab = |a||b|cos = a0*b0 + a1*b1 + a2*b2
GLSL: dot(vec3,vec3) or dot(vec4,vec4)
public double dotprod(double[] a, double[] b) {
return (a[0] * b[0] + a[1] * b[1] + a[2] * b[2]); }
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13. Vector Operations – Cont.
Cross Product (easy for finding the perpendicular vector, or normal)
a×b = a vector perpendicular to a&b
a×b = n|a||b|sin // cross product of two vectors
GLSL: cross(vec3,vec3)
public void crossprod(double[] a, double[] b, double[] v) {
v[0] = a[1] * b[2] - a[2] * b[1];
v[1] = a[2] * b[0] - a[0] * b[2];
v[2] = a[0] * b[1] - a[1] * b[0]; }
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14. @ 2017 by Jim X. Chen: jchen@cs.gmu.edu
Reflect v1 around n to v2 n v1 v2
n is normalized;
dotprod(v1,n) is the projection length of v1 on n
2*dotprod(v1,n) is twice of the above
2*dotprod(v1,n)*n is the vector along n with the length
The above minus v1 will give you v2 v1 v2 v1 v2 v1 v2
@ 2017 by Jim X. Chen:

15. @ 2017 by Jim X. Chen: jchen@cs.gmu.edu
Reflect v1 around n to v2 n v1 v2
// reflect v1 around n to v2 public void reflect(double v1[], double n[], double v2[]) { // v2 = 2*dot(v1, n)*n + v1 for (int i = 0; i < 3; i++) { v2[i] = 2 * dotprod(v1, n) * n[i] - v1[i]; } GLSL: reflect(v1, n); v1 v2 v1 v2 v1 v2
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16. @ 2017 by Jim X. Chen: jchen@cs.gmu.edu
HW1: due before next class
draw points that moves slowly along a circle
Draw multiple points that move and bounce inside the circle
Draw multiple points that bounces outside a circle and inside a rectangle
@ 2017 by Jim X. Chen:
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