How to setup gluLookat() and glOrtho() in openGL? - c

Question

I am new to openGL and have a hard time to understand how to actually parametrize the function gluLookat. I what it does but don't know how to know which parameters I should pass to that function and what consequences it will have.
This is my current code and strangely enough I don't even see the axis I drew... I think it is due to the parameters I pass to the function gluLookAt();
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <GL/glut.h>
void init(void)
{
glClearColor(0.8, 0.8, 0.8, 0.0); /* window color white */
glEnable(GL_DEPTH_TEST);
}
void drawScene(void)
{
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(3.0,3.0,3.0, 0.0,0.0,0.0, 0.0,1.0,0.0);
//used some random parameters...
gluLookAt(0.0, 0.0, 0.0, 5.0, 5.0, 5.0, 0, 1, 0);
//axis
//x
glColor3f(1.0,0.0,0.0);
glLineWidth(1.0);
glBegin(GL_LINES);
glVertex3d(0.0,0.0,0.0);
glVertex3d(1.0,0.0,0.0);
glEnd();
//y
glColor3f(0.0,1.0,0.0);
glLineWidth(1.0);
glBegin(GL_LINES);
glVertex3d(0.0,0.0,0.0);
glVertex3d(1.0,0.0,0.0);
glEnd();
//z
glColor3f(0.0,0.0,1.0);
glLineWidth(1.0);
glBegin(GL_LINES);
glVertex3d(0.0,0.0,0.0);
glVertex3d(1.0,0.0,0.0);
glEnd();
glFlush();
}
void herschaal(){
glViewport(0,0,500,500);
glMatrixMode(GL_PROJECTION);
glOrtho(-10, 10, 10, -10, 10, -10);
glLoadIdentity();
}
int main( int argc, char * argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH );
glutInitWindowPosition(50, 100);
glutInitWindowSize(500, 500);
glutCreateWindow("mijn test");
glutReshapeFunc(herschaal);
init();
glutDisplayFunc(drawScene);
glutMainLoop();
return 0;
}