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: jchen@cs.gmu.edu .1.

@ 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 @ 2017 by Jim X. Chen: jchen@cs.gmu.edu .2.

@ 2017 by Jim X. Chen: jchen@cs.gmu.edu 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 @ 2017 by Jim X. Chen: jchen@cs.gmu.edu .3.

@ 2017 by Jim X. Chen: jchen@cs.gmu.edu 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 @ 2017 by Jim X. Chen: jchen@cs.gmu.edu .4.

@ 2017 by Jim X. Chen: jchen@cs.gmu.edu 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 @ 2017 by Jim X. Chen: jchen@cs.gmu.edu

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 @ 2017 by Jim X. Chen: jchen@cs.gmu.edu

@ 2017 by Jim X. Chen: jchen@cs.gmu.edu 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. @ 2017 by Jim X. Chen: jchen@cs.gmu.edu .7.

@ 2017 by Jim X. Chen: jchen@cs.gmu.edu 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 @ 2017 by Jim X. Chen: jchen@cs.gmu.edu

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: jchen@cs.gmu.edu

@ 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 @ 2017 by Jim X. Chen: jchen@cs.gmu.edu .10.

@ 2017 by Jim X. Chen: jchen@cs.gmu.edu 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) @ 2017 by Jim X. Chen: jchen@cs.gmu.edu

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]); } @ 2017 by Jim X. Chen: jchen@cs.gmu.edu

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]; } @ 2017 by Jim X. Chen: jchen@cs.gmu.edu

@ 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: jchen@cs.gmu.edu

@ 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 @ 2017 by Jim X. Chen: jchen@cs.gmu.edu

@ 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: jchen@cs.gmu.edu .16.