[from Josh] OpenGL code

I propose that if ones wishes to post code then they post it between "pre" tags so that they preserve formatting and allow others to test their code out.

"look at how I did this under HTML view to see what a pre tag is"

The way that I have built my code everything that is needed to run the simulation (such as "math.h", "freeglut.h",...etc) is "#include"ed in one header file. Also within that header file I define the global variables that will be used for the simulation such as number of particles, current runtime, dt, solar mass,... etc. I also define a class object called particle and define a dynamic array of particle objects. I then include this first header file in another header file called "forces.h". In the header file "forces.h" I define all the different forces that I want to take effect in my simulation (currently just gravitational but its very easy to add in other forces). I then include the forces header file into another header file called "movePos.h". In "movPos.h" all the numerical integration takes place. It calls functions from "forces.h" to do so and updates the particles positions. I then include "movePos.h" into my graphic header called "3Ddisplay.h" which I have posted below. Here, within my render function I call functions in "movePos.h" which update the particle object array that I defined in the very first header file. I then graph the positions of each of the particles adding visualization techniques and also display data.

Up until now everything has been contained in seperate header files that are easily updated, debugged, and managed. You should know that header files release their properties to any file that includes them, (ie. things that include header files inherit all things within the header files). I then have a file (not a header) called "main.cpp". This file includes "3Ddisplay.h" and thus inherits all the other header files functions and global variables. In "main.cpp" I define a single function called "main" that interactivity asks the user what type of simulation they would like to perform, what the parameters of the simulation are and then calls the displaySim function in "3Ddisplay.h" which then displays the simulation as you requested. The program is terminated when the user presses "q" in the display window.

Also my simulation utilizes openMP and will run in parallel across all available CPU cores.

I tested my program using "extern" variables instead of in inherited header variables but the complexity rose considerably and made debugging a nightmare. I also test various pointer array object declaration techniques to see which one was the fastest and I found that the using my current method of memory allocation is the fastest. This is similar to the way we would do things with CUDA too since CUDA works fastest with "pinned memory" (memory that is allocated once and remains static for the remainder of the program).

If you would like to use the below code you will have to either a) modify it completely so that it works with your code format, or b) try and follow my format.

In general you really only need to do two things:
- change displaySim function to "main" and add #include freeglut.h at the top of your program
- in the render function replace the movePos3D with your own code that updates particle positions. (Note where it says pPart[i] is my particle object and you should replace it with what ever your particle is or the corresponding x,y,z,vx,vy,vz of your code.

Note: you will need to have freeglut installed on your system and locatable by your compiler. See my previous post on the topic for those using windows.

#include "movePos.h"

/*openGL vars*/
static int left_click = GLUT_UP;
static int right_click = GLUT_UP;
static int xold;
static int yold;
static int width;
static int height;
static int wh;
static int hw;
static int vidtype = 'n';
static int leavetrail = 0;
static int paused = 0;
static double rotate_x = 30;
static double rotate_y = 15;
static double alpha = 0;
static double beta = 0;
static double scale = 100;
static double trans = -0.1*scale;

/*openGL functions*/
void ReshapeFunc(int new_width, int new_height){
width = (double)new_width;
height = (double)new_height;

hw = height / (double) width;
wh = width / (double) height;

glMatrixMode(GL_PROJECTION);

glLoadIdentity();
gluPerspective(20 * sqrt(double(1 + hw * hw)), wh, 8, 12);

glMatrixMode(GL_MODELVIEW);
glutPostRedisplay();
}

void MotionFunc(int x, int y){
if (GLUT_DOWN == left_click){
rotate_y = rotate_y + (y - yold) / 5.f;
rotate_x = rotate_x + (x - xold) / 5.f;
if (rotate_y > 90) rotate_y = 90;
if (rotate_y < -90) rotate_y = -90;   glutPostRedisplay();  }  if (GLUT_DOWN == right_click){   beta = beta + (y - yold) / 2.f;   alpha = alpha + (x - xold) / 2.f;   glutPostRedisplay();  }  xold = x;  yold = y; }  void keyCB(unsigned char key, int x, int y){  if( key == 'q' ){   free(pPart);   exit(0);  }  if( key == '+' ){   scale *= 2.0/3.0;  }  if( key == '-' ){   scale *= 1.5;  }  if( key == 'r' ){   vidtype = 'r';  }  if( key == 'v' ){   vidtype = 'v';  }  if( key == 'n' ){   vidtype = 'n';  }  if( key == 't' ){   leavetrail = abs(leavetrail - 1);  }  if( key == 'p' ){   paused = abs(paused - 1);  } }  void renderBitmapCharacher(float x, float y, float z, void *font,char *string){  char *c;  glRasterPos3f(x,y,z);  for (c=string; *c != '\0'; c++){   glutBitmapCharacter(font, *c);  } }  void Render(int face){  double D;  int i;  /* Axis */  glBegin(GL_LINES);  glColor3d(1, 0, 0); glVertex3d(-0.7*scale, -0.7*scale, -0.7*scale); glVertex3d( 0.7*scale, -0.7*scale, -0.7*scale);  glColor3d(0, 1, 0); glVertex3d(-0.7*scale, -0.7*scale, -0.7*scale); glVertex3d(-0.7*scale,  0.7*scale, -0.7*scale);  glColor3d(0, 0, 1); glVertex3d(-0.7*scale, -0.7*scale, -0.7*scale); glVertex3d(-0.7*scale, -0.7*scale,  0.7*scale);  glEnd();   glRotated(beta, 1, 0, 0);  glRotated(alpha, 0, 1, 0);  glColor3d(1, 1, 1);     glBegin(GL_POINTS);  if (face==0) movePos3D();  KE = 0.0;  #pragma omp parallel for  for (i=0;i width)
glOrtho(-scale, scale, -scale * hw, scale * hw, -scale, scale);
else
glOrtho(-scale * wh, scale * wh, -scale, scale, -scale, scale);


glMatrixMode(GL_MODELVIEW);
/* Perspective view */
glViewport(0, 0, width / 2, height / 2);
glPushMatrix();

/* Display data */
char Npart_str[33];
sprintf(Npart_str,"N=%d",Npart);
renderBitmapCharacher(-scale,scale - 0*scale*0.06,0,(void *)GLUT_BITMAP_8_BY_13,Npart_str);
char G_str[33];
sprintf(G_str,"G=%2.4Lf",G);
renderBitmapCharacher(-scale,scale - 1*scale*0.06,0,(void *)GLUT_BITMAP_8_BY_13,G_str);
char t_str[33];
sprintf(t_str,"t=%2.4Lf",t);
renderBitmapCharacher(-scale,scale - 2*scale*0.06,0,(void *)GLUT_BITMAP_8_BY_13,t_str);
char h_str[33];
sprintf(h_str,"h=%2.4Lf",h);
renderBitmapCharacher(-scale,scale - 3*scale*0.06,0,(void *)GLUT_BITMAP_8_BY_13,h_str);
char scale_str[33];
sprintf(scale_str,"axis scale=%2.4Lf",scale*2);
renderBitmapCharacher(-scale,scale - 4*scale*0.06,0,(void *)GLUT_BITMAP_8_BY_13,scale_str);
char K_str[33];
sprintf(K_str,"Kinetic Energy=%2.4Lf",KE);
renderBitmapCharacher(-scale,scale - 5*scale*0.06,0,(void *)GLUT_BITMAP_8_BY_13,K_str);

glTranslated(0,0,trans);
glRotated(rotate_y, 1, 0, 0);
glRotated(rotate_x, 0, 1, 0);
Render(0);
glPopMatrix();

/* Right view */
glViewport(0, height / 2 + 1, width / 2 + 1, height / 2);
glPushMatrix();
glRotated(90, 0, -1, 0);
Render(1);
glPopMatrix();

/* Face view */
glViewport(width / 2 + 1, height / 2 + 1, width / 2, height / 2);
glPushMatrix();
Render(2);
glPopMatrix();

/* Top view */
glViewport(width / 2 + 1, 0, width / 2, height / 2);
glPushMatrix();
glRotated(90, 1, 0, 0);
Render(3);
glPopMatrix();

/* Projection matrix is restored */
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);

/* End */
glFlush();
glutSwapBuffers();
}


/* Run upon click */
void MouseFunc(int button, int state, int x, int y)
{
if (GLUT_LEFT_BUTTON == button)
  left_click = state;
if (GLUT_RIGHT_BUTTON == button)
  right_click = state;
xold = x;
yold = y;
}

/* Timed refresh to control refresh rate */
void TimerdisplayCB(int value){
if (paused == 0) glutPostRedisplay();
glutTimerFunc(33,TimerdisplayCB,value);
}


void displaySim(int *argcp, char **argv){
/* Creation of the window */
glutInit(argcp, argv);
glutInitDisplayMode(GLUT_RGBA);
glutInitWindowSize(glutGet(GLUT_SCREEN_WIDTH),glutGet(GLUT_SCREEN_HEIGHT));
glutCreateWindow("Particle Simulation");

/* OpenGL settings */
glClearColor(0, 0, 0, 0);
glEnable(GL_CULL_FACE);
glCullFace(GL_BACK);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

/* Declaration of the callbacks */
glutDisplayFunc(DisplayFunc);
glutReshapeFunc(ReshapeFunc);
glutKeyboardFunc(keyCB);
glutMouseFunc(MouseFunc);
glutMotionFunc(MotionFunc);
glutTimerFunc(33,TimerdisplayCB,0);

/* Main display */
glutMainLoop();
}