Opengl and c++ drawing multiple cubes - c++

Question

So I am able to draw a cube, but I want to draw multiple cubes, and I don't know how. Can you guys help me?
This is the code of how I draw the cube:
#include <GL/freeglut.h>
#include <stdlib.h>
void initGL(int width, int height)
{
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,2.0f,100.0f);
glMatrixMode(GL_MODELVIEW);
const GLfloat light_ambient[] = { 0.0f, 0.0f, 0.0f, 1.0f };
const GLfloat light_diffuse[] = { 1.0f, 1.0f, 1.0f, 1.0f };
const GLfloat light_specular[] = { 1.0f, 1.0f, 1.0f, 1.0f };
const GLfloat light_position[] = { 2.0f, 5.0f, 5.0f, 0.0f };
const GLfloat mat_ambient[] = { 0.7f, 0.7f, 0.7f, 1.0f };
const GLfloat mat_diffuse[] = { 0.8f, 0.8f, 0.8f, 1.0f };
const GLfloat mat_specular[] = { 1.0f, 1.0f, 1.0f, 1.0f };
const GLfloat high_shininess[] = { 100.0f };
glEnable(GL_LIGHT0);glEnable(GL_LIGHTING);
glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);
glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
glLightfv(GL_LIGHT0, GL_SPECULAR, light_specular);
glLightfv(GL_LIGHT0, GL_POSITION, light_position);
glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);
glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
glMaterialfv(GL_FRONT, GL_SHININESS, high_shininess);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,2.0f,100.0f);
glMatrixMode(GL_MODELVIEW);
glEnable(GL_CULL_FACE);glCullFace(GL_BACK);
}
static void display(void)
{
glLoadIdentity();
glPushMatrix();
glTranslatef(0.0,0.0,-10);
glRotatef(60,1,0,0);
glRotatef(60,0,1,0);
glutSolidCube(2);
glLoadIdentity();
glTranslatef(0.0,0.0,-10);
glRotatef(60,1,0,0);
glRotatef(60,0,1,0);
glutSolidCube(2);
glPopMatrix();
glFlush();
}
static void idle(void)
{
glutPostRedisplay();
}
int main(int argc, char *argv[])
{
int width = 640;
int height = 480;
glutInit(&argc, argv);
glutInitWindowSize(width,height);
glutInitWindowPosition(10,10);
glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
glutCreateWindow("Lab 1: Hello OpenGL World !");
glutDisplayFunc(display);
glutIdleFunc(idle);
initGL(width, height);
glutMainLoop();
return EXIT_SUCCESS;
}
I need to draw multiple cubes like the one that I am drawing. I tried with a for but I just started opengl today and don't know what I'm doing. I have tried multiple things and got very annoyed. Do you also recommend any book?

Answer 1

"I just started opengl today"
It will take a while to fully understand OpenGL but if you had consulted your study material, you should have spoted a few errors in you code.
You need to define a glutReshapeFunc function: without this your viewport is undefined. #KevinSpaghetti is also right your glutDisplayFunc has a bug: all cubes are drawn at the same position and a model-view matrix was not specified.
Here is a code that actually works.
#include <GL/glew.h>
#include <GL/freeglut.h>
#include <iostream>
/*******************************************************************************
********************************************************************************
********************************************************************************/
struct { int width = 640; int height = 480; } window;
/*******************************************************************************
********************************************************************************
********************************************************************************/
void resize(int width, int height)
{
glViewport(0, 0, (window.width = width), (window.height = height));
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45, ((GLdouble)window.width / window.height), 2, 100);
glMatrixMode(GL_MODELVIEW);
}
/*******************************************************************************
********************************************************************************
********************************************************************************/
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(0, 0, 30, 0, 0, 0, 0, 1, 0);
glRotatef(-30, 0, 1, 0); // <----- rotate entire scene by 30 degrees
glColor3f(0.5f, 0.0f, 0.0f);
for (int i = 0; i < 3; ++i) // <----- draw three cubes
{
glPushMatrix();
glRotatef(60, 1.0, 0.0, 0.0);
glRotatef(60, 0.0, 0.1, 0.0);
glutSolidCube(5);
glPopMatrix();
glTranslatef(0.0, 0.0, -10.0f);
}
glFlush();
}
/*******************************************************************************
********************************************************************************
********************************************************************************/
void initGL(void)
{
glClearColor(0.8f, 0.8f, 0.8f, 1.0f);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glEnable(GL_CULL_FACE);
glCullFace(GL_BACK);
glFrontFace(GL_CCW);
const GLfloat light_ambient[] = { 0.0f, 0.0f, 0.0f, 1.0f };
const GLfloat light_diffuse[] = { 1.0f, 1.0f, 1.0f, 1.0f };
const GLfloat light_specular[] = { 1.0f, 1.0f, 1.0f, 1.0f };
const GLfloat light_position[] = { 2.0f, 5.0f, 5.0f, 0.0f };
const GLfloat mat_ambient[] = { 0.7f, 0.7f, 0.7f, 1.0f };
const GLfloat mat_diffuse[] = { 0.8f, 0.8f, 0.8f, 1.0f };
const GLfloat mat_specular[] = { 1.0f, 1.0f, 1.0f, 1.0f };
const GLfloat high_shininess[] = { 100.0f };
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);
glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
glLightfv(GL_LIGHT0, GL_SPECULAR, light_specular);
glLightfv(GL_LIGHT0, GL_POSITION, light_position);
glEnable(GL_COLOR_MATERIAL);
glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);
glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
glMaterialfv(GL_FRONT, GL_SHININESS, high_shininess);
}
/*******************************************************************************
********************************************************************************
********************************************************************************/
int main(int argc, char *argv[])
{
//.....................
glutInit(&argc, argv);
glutInitContextFlags(GLUT_FORWARD_COMPATIBLE);
glutInitContextProfile(GLUT_COMPATIBILITY_PROFILE);
glutSetOption(GLUT_ACTION_ON_WINDOW_CLOSE, GLUT_ACTION_GLUTMAINLOOP_RETURNS);
glutInitWindowSize(window.width, window.height);
glutInitWindowPosition(10, 10);
glutInitDisplayMode(GLUT_DEPTH | GLUT_RGB | GLUT_SINGLE);
glutCreateWindow("Lab 1: Hello OpenGL World !");
if (glewInit() != GLEW_OK) exit(EXIT_FAILURE);
glutReshapeFunc(resize);
glutDisplayFunc(display);
initGL();
glutMainLoop();
std::cout << "...it worked!";
//.....................
return 0;
}
I would recommend: OpenGL Programming Guide. It is old OpenGl but still relevant.

Answer 2

glPushMatrix();
glTranslatef(0.0,0.0,-10);
glRotatef(60,1,0,0);
glRotatef(60,0,1,0);
glutSolidCube(2);
glLoadIdentity();
glTranslatef(0.0,0.0,-10);
glRotatef(60,1,0,0);
glRotatef(60,0,1,0);
glutSolidCube(2);
glPopMatrix();
Here it seems that you are drawing 2 cubes in the same position, so the second is drawn over the first, try changing the code to
glPushMatrix();
glTranslatef(2,0.0,-10);
glRotatef(60,1,0,0);
glRotatef(60,0,1,0);
glutSolidCube(2);
glLoadIdentity();
glTranslatef(0.0,0.0,-10);
glRotatef(60,1,0,0);
glRotatef(60,0,1,0);
glutSolidCube(2);
glPopMatrix();