OpenGL Screencast 11: Code Organization

011.c

#include "screencasts.h"

/*
 *  main()
 *  ----
 *  Start up GLUT and tell it what to do
 */
int main(int argc,char* argv[])
{
  initializeGlobals();
  glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
  glutInitWindowSize(windowWidth,windowHeight);
  glutCreateWindow(windowName);

  glutDisplayFunc(display);
  glutReshapeFunc(displayReshape);
  glutKeyboardFunc(windowKey);
  glutSpecialFunc(windowSpecial);

  glutMainLoop();
  return 0;
}

common.h

/*  Poor man's approximation of PI */
#define PI 3.1415926535898
/*  Macro for sin & cos in degrees */
#define Cos(th) cos(PI/180*(th))
#define Sin(th) sin(PI/180*(th))
/*  D degrees of rotation */
#define DEF_D 5

display.c

#include "screencasts.h"

/*
 *  displayInit
 *  -------
 *  Initializes display
 */
void displayInit()
{
  glClearColor(0.0,0.0,0.0,0.0);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
  glEnable(GL_DEPTH_TEST);
  glLoadIdentity();
}

/*
 * displayEye()
 * ------
 * Set the eye position
 */
void displayEye()
{
  if (toggleMode) {
    double Ex = -2*dim*Sin(th)*Cos(ph);
    double Ey = +2*dim        *Sin(ph);
    double Ez = +2*dim*Cos(th)*Cos(ph);
    /* camera/eye position, aim of camera lens, up-vector */
    gluLookAt(Ex,Ey,Ez , 0,0,0 , 0,Cos(ph),0);
  }
  /*  Orthogonal - set world orientation */
  else {
    glRotatef(ph,1,0,0);
    glRotatef(th,0,1,0);
  }
}

/*
 *  displayReshape()
 *  ------
 *  GLUT calls this routine when the window is resized
 */
void displayReshape(int width,int height)
{
  asp = (height>0) ? (double)width/height : 1;
  glViewport(0,0, width,height);
  displayProject();
}

/*
 * displayProject()
 * ------
 * Sets the projection
 */
void displayProject() 
{
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();

  if (toggleMode) {
    /* perspective */
    gluPerspective(fov,asp,dim/4,4*dim);
  }
  else {
    /* orthogonal projection*/
    glOrtho(-dim*asp,+dim*asp, -dim,+dim, -dim,+dim);
  }

  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}

/*
 *  display()
 *  ------
 *  Display the scene
 */
void display()
{
  /* setup functions */  
  displayInit();
  displayEye();

  /* draw */
  drawAxes();
  drawValues();

  /* magic here */
  drawScene();

  glFlush();
  glutSwapBuffers();

  errCheck("display sanity check");
}

display.h

void displayInit(void);
void displayEye(void);
void displayReshape(int width,int height);
void displayProject(void);
void display(void);

draw.c

#include "screencasts.h"

/*
 * drawAxes()
 * ------
 * Draw the axes
 */
void drawAxes() 
{
  if (toggleAxes) {
    /*  Length of axes */
    double len = 2.0;
    glColor3f(1.0,1.0,1.0);
    glBegin(GL_LINES);
    glVertex3d(0,0,0);
    glVertex3d(len,0,0);
    glVertex3d(0,0,0);
    glVertex3d(0,len,0);
    glVertex3d(0,0,0);
    glVertex3d(0,0,len);
    glEnd();
    /*  Label axes */
    glRasterPos3d(len,0,0);
    print("X");
    glRasterPos3d(0,len,0);
    print("Y");
    glRasterPos3d(0,0,len);
    print("Z");
  }
}

/*
 *  drawValues()
 *  ------
 *  Draw the values in the lower left corner
 */
void drawValues()
{
  if (toggleValues) {
    glColor3f(0.8,0.8,0.8);
    printAt(5,5,"View Angle (th, ph) =(%d, %d)", th,ph);
    printAt(5,25,"Projection mode =(%s)", toggleMode?"Perspective":"Orthogonal");
  }
}

void drawScene()
{
  /*
  cube(1,0,1, 1,1,1, 0);
  cube(-1,0,1, 1,1,1, 0);
  cone(0,1,0, 1,1,DEF_D);
  cone(0,-1,0, 1,1,90);
  */

  /* a 'tower' */
  /*
  cube(0,1.5,0, 1,3,1, 0);
  cube(0,3.5,0, 2,1,2, 45);
  spike(0,1,-3.5, 0.5,1, 90, 90,0,0);
  spike(0,1,3.5, 0.5,1, 90, -90,0,0);
  spike(-3.5,1,0, 0.5,1, 90, 0,0,-90);
  spike(3.5,1,0, 0.5,1, 90, 0,0,90);
  */
  tower(0,0,0, 1,1,1, 0);
  tower(4,0,0, 1,1,1.5, 30);
}

draw.h

void drawAxes(void);
void drawValues(void);
void drawScene(void);

error.c

#include "screencasts.h"

void errCheck(char* where)
{
   int err = glGetError();
   if (err) fprintf(stderr,"ERROR: %s [%s]\n",gluErrorString(err),where);
}

error.h

void errCheck(char* where);

globals.c

#include "screencasts.h"

char *windowName = "OpenGL screenscasts 11: Code Organization";
int windowWidth = 500;
int windowHeight = 450;

int toggleAxes = 1;
int toggleValues = 1;
int toggleMode = 0;

double dim = 5.0;
int th = 340;
int ph = 30;
int fov = 55;
int asp = 1;

Makefile

# Target to build
#TARGET = 011
TARGET = 011
#EXECS = ./executables/011
EXECS = ./executables/011

# Libraries - LINUX
#LIBS=-lglut -lGLU
# Libraries - OSX
LIBS=-framework OpenGL -framework GLUT

all: $(TARGET)

# Generic compile rules
.c.o: 
	gcc -c -O -Wall $<

# Generic compile and link
%: %.c screencasts.a
	gcc -Wall -O3 -o ./executables/$@ $^ $(LIBS)

clean:
	rm -f $(EXECS) *.o *.a

# without .h => globals.o
screencasts.a:globals.o print.o error.o shapes.o models.o interaction.o initialization.o draw.o display.o
	ar -rcs screencasts.a $^