Blank screen when running and no errors

Ran the code and no errors. A blank screen appear. Can't see where I went wrong after I edited this section of the code.

Trying to integrate a planet system of 4 planets and 1 sun. The program was running and showing the system, but once I edited this section of the code. It became blank screen.

planetsystem.cpp

#include <string>
using namespace std;    // to avoid having to use std::

#define GLEW_STATIC     // include GLEW as a static library
#include <GLEW/glew.h>  // include GLEW
#include <GLFW/glfw3.h> // include GLFW (which includes the OpenGL header)
#include <glm/glm.hpp>  // include GLM (ideally should only use the GLM headers that are actually used)
#include <glm/gtx/transform.hpp>
using namespace glm;    // to avoid having to use glm::

#include "shader.h"
#include "camera.h"

#define PI 3.14159265
#define MAX_SLICES 50
#define MIN_SLICES 8
#define MAX_VERTICES (MAX_SLICES+2)*3   // a triangle fan should have a minimum of 3 vertices
#define CIRCLE_RADIUS 3.0
#define WINDOW_WIDTH 1000
#define WINDOW_HEIGHT 1000

// struct for vertex attributes
struct Vertex
{
    GLfloat position[3];
    GLfloat color[3];
};

// global variables

GLfloat g_vertices_circle[MAX_VERTICES] = {
    0.0f, 0.0f, 0.0f,
    0.0f, 0.0f, 0.0f
};

GLfloat g_colors_circle[MAX_VERTICES] = {
    1.0f, 0.0f, 0.0f,
    1.0f, 0.0f, 0.0f
};

GLuint g_slices = MAX_SLICES;   // number of circle slices

Vertex g_vertices[] = {
    // vertex 1
    -0.5f, 0.5f, 0.5f,  // position
    1.0f, 0.0f, 1.0f,   // colour
    // vertex 2
    -0.5f, -0.5f, 0.5f, // position
    1.0f, 0.0f, 0.0f,   // colour
    // vertex 3
    0.5f, 0.5f, 0.5f,   // position
    1.0f, 1.0f, 1.0f,   // colour
    // vertex 4
    0.5f, -0.5f, 0.5f,  // position
    1.0f, 1.0f, 0.0f,   // colour
    // vertex 5
    -0.5f, 0.5f, -0.5f, // position
    0.0f, 0.0f, 1.0f,   // colour
    // vertex 6
    -0.5f, -0.5f, -0.5f,// position
    0.0f, 0.0f, 0.0f,   // colour
    // vertex 7
    0.5f, 0.5f, -0.5f,  // position
    0.0f, 1.0f, 1.0f,   // colour
    // vertex 8
    0.5f, -0.5f, -0.5f, // position
    0.0f, 1.0f, 0.0f,   // colour
};

GLuint g_indices[] = {
    0, 1, 2,    // triangle 1
    2, 1, 3,    // triangle 2
    4, 5, 0,    // triangle 3
    0, 5, 1,    // ...
    2, 3, 6,
    6, 3, 7,
    4, 0, 6,
    6, 0, 2,
    1, 5, 3,
    3, 5, 7,
    5, 4, 7,
    7, 4, 6,    // triangle 12
};

GLuint g_IBO = 0;               // index buffer object identifier
GLuint g_VBO[3];                // vertex buffer object identifier
GLuint g_VAO[2];                // vertex array object identifier
GLuint g_shaderProgramID = 0;   // shader program identifier
GLuint g_MVP_Index = 0;         // location in shader
GLuint g_alphaIndex;            // for transparency of 4th planet
glm::mat4 g_modelMatrix[5];     // planets object model matrices
glm::mat4 g_modelMatrixCircle[5];// circle model matrices
glm::mat4 g_modelMatrixSubPlanets[5];// object matrices for sub-planets (moon, disc etc)
glm::mat4 g_viewMatrix;         // view matrix
glm::mat4 g_projectionMatrix;   // projection matrix

Camera g_camera;            // camera 

float g_orbitSpeed[5] = { 0.3f, 0.5f, 0.4f, 0.2f, 0.1f };       // for speed of rotation around sun
float g_rotationSpeed[5] = { 0.07f, 0.7f, 3.0f, 5.0f, 1.0f };   // for speed of rotation on own axis
float g_scaleSize[5] = { 0.5f, 0.5f, 0.5f, 0.5f, 0.5f };        // for scaling the orbiting planets
float g_axisOfRotation[5] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, };  // for offsetting the axis of rotation
float g_alpha = 0.5f;       // transparency of 4th planet
bool g_enableAnimation = true;

void generate_circle()
{
    float angle = PI * 2 / static_cast<float>(g_slices);    // used to generate x and y coordinates
    float scale_factor = static_cast<float>(WINDOW_HEIGHT) / WINDOW_WIDTH;  // scale to make it a circle instead of an elipse
    int index = 0;  // vertex index

    g_vertices_circle[3] = CIRCLE_RADIUS * scale_factor;    // set x coordinate of vertex 1

    // generate vertex coordinates for triangle fan
    for (int i = 2; i < g_slices + 2; i++)
    {
        // multiply by 3 because a vertex has x, y, z coordinates
        index = i * 3;

        g_vertices_circle[index] = CIRCLE_RADIUS * cos(angle) * scale_factor;
        g_vertices_circle[index + 1] = CIRCLE_RADIUS * sin(angle);
        g_vertices_circle[index + 2] = 0.0f;

        //Color for edges. See stackoverflow
        g_colors_circle[index] = 1.0f;
        g_colors_circle[index + 1] = 0.0f;
        g_colors_circle[index + 2] = 0.0f;

        // update to next angle
        angle += PI * 2 / static_cast<float>(g_slices);
    }

    // Gets rid of line from middle of circle
    g_vertices_circle[0] = g_vertices_circle[3];
    g_vertices_circle[1] = g_vertices_circle[4];
    g_vertices_circle[2] = g_vertices_circle[5];
}

static void init(GLFWwindow* window)
{
    glClearColor(0.0, 0.0, 0.0, 1.0);   // set clear background colour

    glEnable(GL_DEPTH_TEST);    // enable depth buffer test
    glEnable(GL_BLEND);
    glBlendEquationSeparate(GL_FUNC_ADD, GL_FUNC_ADD);
    glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ZERO);

    // create and compile our GLSL program from the shader files
    g_shaderProgramID = loadShaders("MVP_VS.vert", "ColorFS.frag");

    // find the location of shader variables
    GLuint positionIndex = glGetAttribLocation(g_shaderProgramID, "aPosition");
    GLuint colorIndex = glGetAttribLocation(g_shaderProgramID, "aColor");
    g_MVP_Index = glGetUniformLocation(g_shaderProgramID, "uModelViewProjectionMatrix");
    g_alphaIndex = glGetUniformLocation(g_shaderProgramID, "uAlpha");

    // initialise model matrix to the identity matrix
    g_modelMatrix[0] = g_modelMatrix[1] = g_modelMatrix[2] = g_modelMatrix[3] = g_modelMatrix[4] = glm::mat4(1.0f);
    g_modelMatrixCircle[0] = g_modelMatrixCircle[1] = g_modelMatrixCircle[2] = g_modelMatrixCircle[3] = g_modelMatrixCircle[4] = glm::mat4(1.0f);
    g_modelMatrixSubPlanets[2] = g_modelMatrixSubPlanets[3] = glm::mat4(1.0f);;

    // set camera's view matrix
    g_camera.setViewMatrix(glm::vec3(0, 3, 14), glm::vec3(0, 0, 0), glm::vec3(0, 1, 0));

    int width, height;
    glfwGetFramebufferSize(window, &width, &height);
    float aspectRatio = static_cast<float>(width) / height;

    // set camera's projection matrix
    g_camera.setProjectionMatrix(g_projectionMatrix);

    // initialise projection matrix
    g_projectionMatrix = glm::perspective(45.0f, aspectRatio, 0.1f, 100.0f);

    // generate identifier for VBO and copy data to GPU
    glGenBuffers(1, &g_VBO[0]);
    glBindBuffer(GL_ARRAY_BUFFER, g_VBO[0]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertices), g_vertices, GL_STATIC_DRAW);

    // generate identifier for IBO and copy data to GPU
    glGenBuffers(1, &g_IBO);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_IBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(g_indices), g_indices, GL_STATIC_DRAW);

    // generate identifiers for VAO
    glGenVertexArrays(1, &g_VAO[0]);

    // create VAO and specify VBO data
    glBindVertexArray(g_VAO[0]);
    glBindBuffer(GL_ARRAY_BUFFER, g_VBO[0]);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_IBO);
    // interleaved attributes
    glVertexAttribPointer(positionIndex, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), reinterpret_cast<void*>(offsetof(Vertex, position)));
    glVertexAttribPointer(colorIndex, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), reinterpret_cast<void*>(offsetof(Vertex, color)));

    glEnableVertexAttribArray(positionIndex);   // enable vertex attributes
    glEnableVertexAttribArray(colorIndex);

    /*------------------------Circle----------------------*/

    // generate vertices of triangle fan
    generate_circle();

    // create VBO and buffer the data
    glGenBuffers(1, &g_VBO[1]);
    glBindBuffer(GL_ARRAY_BUFFER, g_VBO[1]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 3 * (g_slices + 2), g_vertices_circle, GL_STATIC_DRAW);

    glGenBuffers(1, &g_VBO[2]);
    glBindBuffer(GL_ARRAY_BUFFER, g_VBO[2]);
    glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 3 * (g_slices + 2), g_colors_circle, GL_STATIC_DRAW);

    // create VAO and specify VBO data
    glGenVertexArrays(1, &g_VAO[1]);
    glBindVertexArray(g_VAO[1]);
    glBindBuffer(GL_ARRAY_BUFFER, g_VBO[1]);
    glVertexAttribPointer(positionIndex, 3, GL_FLOAT, GL_FALSE, 0, 0);  // specify the form of the data
    glBindBuffer(GL_ARRAY_BUFFER, g_VBO[2]);
    glVertexAttribPointer(colorIndex, 3, GL_FLOAT, GL_FALSE, 0, 0); // specify the form of the data

    glEnableVertexAttribArray(positionIndex);   // enable vertex attributes
    glEnableVertexAttribArray(colorIndex);

    /*----------------------------------------------------*/
}

//Generates a random value between 0.1 and 0.9
double generateRandomFloat(float min, float max)
{
    return min + static_cast <float> (rand()) / (static_cast <float> (RAND_MAX / (max - min)));
}

// function used to update the scene
static void update_scene()
{
    // static variables for rotation angles
    static float orbitAngle[5] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, };
    static float rotationAngle[5] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };
    float scaleFactor = 0.05;

    orbitAngle[0] += g_orbitSpeed[0] * scaleFactor;
    orbitAngle[1] += g_orbitSpeed[1] * scaleFactor;
    orbitAngle[2] += g_orbitSpeed[2] * scaleFactor;
    orbitAngle[3] += g_orbitSpeed[3] * scaleFactor;
    orbitAngle[4] += g_orbitSpeed[4] * scaleFactor;

    // update rotation angles
    rotationAngle[0] += g_rotationSpeed[0] * scaleFactor;
    rotationAngle[1] += g_rotationSpeed[1] * scaleFactor;
    rotationAngle[2] += g_rotationSpeed[2] * scaleFactor;
    rotationAngle[3] += g_rotationSpeed[3] * scaleFactor;
    rotationAngle[4] += g_rotationSpeed[4] * scaleFactor;

    // update model matrix (planets)
    g_modelMatrix[0] = glm::rotate(rotationAngle[0], glm::vec3(0.0f, 1.0f, 0.0f));

    g_modelMatrix[1] = glm::translate(glm::vec3(g_axisOfRotation[1], 0.0f, 0.0f))   //moves the axis of rotation along x-axis
        * glm::rotate(orbitAngle[1], glm::vec3(0.0f, 1.0f, 0.0f))
        * glm::translate(glm::vec3(2.0f, 0.0f, 0.0f))
        * glm::rotate(rotationAngle[1], glm::vec3(0.0f, -1.0f, 0.0f))       //enables rotation on own axis. try comment
        * glm::rotate(glm::radians(45.0f), glm::vec3(1.0f, 0.0f, 0.0f))     //rotates into a diamond shape
        * glm::rotate(glm::radians(45.0f), glm::vec3(0.0f, 0.0f, 1.0f))     //rotates into a diamond shape
        * glm::scale(glm::vec3(g_scaleSize[1], g_scaleSize[1], g_scaleSize[1]));

    g_modelMatrix[2] = glm::translate(glm::vec3(g_axisOfRotation[2], 0.0f, 0.0f))
        * glm::rotate(orbitAngle[2], glm::vec3(0.0f, -1.0f, 0.0f))
        * glm::translate(glm::vec3(4.0f, 0.0f, 0.0f))
        * glm::rotate(rotationAngle[2], glm::vec3(0.0f, 1.0f, 0.0f))
        * glm::scale(glm::vec3(g_scaleSize[2], g_scaleSize[2], g_scaleSize[2]));

    g_modelMatrix[3] = glm::translate(glm::vec3(g_axisOfRotation[3], 0.0f, 0.0f))
        * glm::rotate(orbitAngle[3], glm::vec3(0.0f, 1.0f, 0.0f))
        * glm::translate(glm::vec3(6.0f, 0.0f, 0.0f))
        * glm::rotate(rotationAngle[3], glm::vec3(0.0f, 1.0f, 0.0f))
        * glm::scale(glm::vec3(g_scaleSize[3], g_scaleSize[3], g_scaleSize[3]));

    g_modelMatrix[4] = glm::translate(glm::vec3(g_axisOfRotation[4], 0.0f, 0.0f))
        * glm::rotate(orbitAngle[4], glm::vec3(0.0f, -1.0f, 0.0f))  // -y changes orbit to clock-wise
        * glm::translate(glm::vec3(8.0f, 0.0f, 0.0f))
        * glm::rotate(rotationAngle[4], glm::vec3(0.0f, -1.0f, 0.0f))
        * glm::scale(glm::vec3(g_scaleSize[4], g_scaleSize[4], g_scaleSize[4]));

    // update model matrix (orbit paths ie.circles)
    g_modelMatrixCircle[1] = glm::translate(glm::vec3(g_axisOfRotation[1], 0.0f, 0.0f)) * glm::scale(glm::vec3(0.68f, 0.68f, 0.68f)) * glm::rotate(glm::radians(90.0f), glm::vec3(1.0f, 0.0f, 0.0f));
    g_modelMatrixCircle[2] = glm::translate(glm::vec3(g_axisOfRotation[2], 0.0f, 0.0f)) * glm::scale(glm::vec3(1.35f, 1.35f, 1.35f)) * glm::rotate(glm::radians(90.0f), glm::vec3(1.0f, 0.0f, 0.0f));
    g_modelMatrixCircle[3] = glm::translate(glm::vec3(g_axisOfRotation[3], 0.0f, 0.0f)) * glm::scale(glm::vec3(2.0f, 2.0f, 2.0f)) * glm::rotate(glm::radians(90.0f), glm::vec3(1.0f, 0.0f, 0.0f));
    g_modelMatrixCircle[4] = glm::translate(glm::vec3(g_axisOfRotation[4], 0.0f, 0.0f)) * glm::scale(glm::vec3(2.7f, 2.7f, 2.7f)) * glm::rotate(glm::radians(90.0f), glm::vec3(1.0f, 0.0f, 0.0f));

    // update model matrix (mini planets eg. moon)
    g_modelMatrixSubPlanets[2] = glm::translate(glm::vec3(g_axisOfRotation[1], 0.0f, 0.0f))
        * glm::scale(glm::vec3(0.35f, 0.35f, 0.35f))
        * glm::rotate(glm::radians(90.0f), glm::vec3(1.0f, 0.0f, 0.0f));

    g_modelMatrixSubPlanets[3] = glm::translate(glm::vec3(g_axisOfRotation[3], 0.0f, 0.0f))
        * glm::rotate(orbitAngle[3], glm::vec3(0.0f, 1.0f, 0.0f))
        * glm::translate(glm::vec3(6.0f, 0.0f, 0.0f))
        * glm::rotate(rotationAngle[3], glm::vec3(0.0f, 1.0f, 0.0f))
        * glm::scale(glm::vec3(g_scaleSize[3], g_scaleSize[3], g_scaleSize[3]));
}

// function used to render the scene
static void render_scene()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // clear colour buffer and depth buffer

    glUseProgram(g_shaderProgramID);    // use the shaders associated with the shader program

    glm::mat4 MVP = glm::mat4(1.0f);    //ModelViewProjection matrix to be shared. Initialized to identity

//Circle 1
    MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrixCircle[1];
    glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
    glBindVertexArray(g_VAO[1]);            // make VAO active
    glDrawArrays(GL_LINE_LOOP, 0, g_slices + 2);    // display the vertices based on the primitive type

//Circle 2                                              
    MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrixCircle[2];
    glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
    glDrawArrays(GL_LINE_LOOP, 0, g_slices + 2);    // display the vertices based on the primitive type

//Circle 3                                              
    MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrixCircle[3];
    glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
    glDrawArrays(GL_LINE_LOOP, 0, g_slices + 2);    // display the vertices based on the primitive type

//Circle 4                                              
    MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrixCircle[4];;
    glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
    glDrawArrays(GL_LINE_LOOP, 0, g_slices + 2);    // display the vertices based on the primitive type

// Circle for Object 2
    MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrix[2] * g_modelMatrixSubPlanets[2];
    glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
    glDrawArrays(GL_TRIANGLE_FAN, 0, g_slices + 2); // display the vertices based on the primitive type

    glBindVertexArray(g_VAO[0]);        // make VAO active

// Object 1
    MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrix[0];
    glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
    glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0);   // display the vertices based on their indices and primitive type

// Object 2
    MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrix[1];
    glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
    glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0);   // display the vertices based on their indices and primitive type

// Object 3
    MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrix[2];
    glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
    glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0);   // display the vertices based on their indices and primitive type

// Object 4
    MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrix[3];
    glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
    glUniform1fv(g_alphaIndex,1, &g_alpha);
    glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0);   // display the vertices based on their indices and primitive type

// Object 5
    MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrix[4];
    glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
    glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0);   // display the vertices based on their indices and primitive type

// Moon for Object 3
    MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrixSubPlanets[3] * g_modelMatrix[4];
    glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
    glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0);   // display the vertices based on their indices and primitive type

    glFlush();  // flush the pipeline
}

static void cursor_position_callback(GLFWwindow* window, double xpos, double ypos)
{
    // variables to store mouse cursor coordinates
    static double previous_xpos = xpos;
    static double previous_ypos = ypos;
    double delta_x = xpos - previous_xpos;
    double delta_y = ypos - previous_ypos;

    // pass mouse movement to camera class
    g_camera.updateYaw(delta_x);
    g_camera.updatePitch(delta_y);

    // update previous mouse coordinates
    previous_xpos = xpos;
    previous_ypos = ypos;
}

// key press or release callback function
static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
    // quit if the ESCAPE key was press
    if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
    {
        // set flag to close the window
        glfwSetWindowShouldClose(window, GL_TRUE);
        return;
    }
    // toggle animation
    else if (key == GLFW_KEY_P && action == GLFW_PRESS) {
        static int count = 1;

        if (count % 2 == 0)
            g_enableAnimation = true;
        else
            g_enableAnimation = false;

        count++;
    }
    // render in perspective view
    else if (key == GLFW_KEY_1 && action == GLFW_PRESS) {
        cout << "Perspective-View" << endl << endl;
        // set camera's view matrix
        g_camera.setViewMatrix(glm::vec3(0, 3, 14), glm::vec3(0, 0, 0), glm::vec3(0, 1, 0));
        render_scene();
    }
    // render from top view
    else if (key == GLFW_KEY_2 && action == GLFW_PRESS) {
        cout << "Top-View" << endl << endl;
        // set camera's view matrix
        g_camera.setViewMatrix(glm::vec3(0, 15, 0), glm::vec3(0, 0, 0), glm::vec3(0, 0,-1));
        render_scene();
    }

    // Randomize size, orbit speed, axis rotation speed of planets
    else if (key == GLFW_KEY_R && action == GLFW_PRESS) {

        // Randomize planet size
        g_scaleSize[1] = generateRandomFloat(0.1, 0.75);
        g_scaleSize[2] = generateRandomFloat(0.1, 0.75);
        g_scaleSize[3] = generateRandomFloat(0.1, 0.75);
        g_scaleSize[4] = generateRandomFloat(0.1, 0.75);

        // Randomize speed of rotation (on planets own axis)
        g_rotationSpeed[1] = generateRandomFloat(0.1, 2.0);
        g_rotationSpeed[2] = generateRandomFloat(0.1, 2.0);
        g_rotationSpeed[3] = generateRandomFloat(0.1, 2.0);
        g_rotationSpeed[4] = generateRandomFloat(0.1, 2.0);

        // Randomize speed of rotation around sun
        g_orbitSpeed[1] = generateRandomFloat(0.1, 0.7);
        g_orbitSpeed[2] = generateRandomFloat(0.1, 0.7);
        g_orbitSpeed[3] = generateRandomFloat(0.1, 0.7);
        g_orbitSpeed[4] = generateRandomFloat(0.1, 0.7);

        // Randomize offset for axis of rotation
        g_axisOfRotation[1] = generateRandomFloat(-0.5, 0.5);
        g_axisOfRotation[2] = generateRandomFloat(-0.5, 0.5);
        g_axisOfRotation[3] = generateRandomFloat(-0.5, 0.5);
        g_axisOfRotation[4] = generateRandomFloat(-0.5, 0.5);

        // Display info for each planet
        cout << "PLANET 1 - \tSize: " << g_scaleSize[1] << "\tSpeed: " << g_rotationSpeed[1]
            << "\tOrbit Speed: " << g_orbitSpeed[1] << "\tAxis offset: " << g_axisOfRotation[1] << endl;
        cout << "PLANET 2 - \tSize: " << g_scaleSize[2] << "\tSpeed: " << g_rotationSpeed[2]
            << "\tOrbit Speed: " << g_orbitSpeed[2] << "\tAxis offset: " << g_axisOfRotation[2] << endl;
        cout << "PLANET 3 - \tSize: " << g_scaleSize[3] << "\tSpeed: " << g_rotationSpeed[3]
            << "\tOrbit Speed: " << g_orbitSpeed[3] << "\tAxis offset: " << g_axisOfRotation[3] << endl;
        cout << "PLANET 4 - \tSize: " << g_scaleSize[4] << "\tSpeed: " << g_rotationSpeed[4]
            << "\tOrbit Speed: " << g_orbitSpeed[4] << "\tAxis offset: " << g_axisOfRotation[4] << endl;
        cout << endl;

        render_scene();
    }
}

// error callback function
static void error_callback(int error, const char* description)
{
    cerr << description << endl;    // output error description
}

int main(void)
{
    GLFWwindow* window = NULL;  // pointer to a GLFW window handle

    glfwSetErrorCallback(error_callback);   // set error callback function

    // initialise GLFW
    if (!glfwInit())
    {
        // if failed to initialise GLFW
        exit(EXIT_FAILURE);
    }

    // minimum OpenGL version 3.3
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);

    // create a window and its OpenGL context
    window = glfwCreateWindow(1000, 1000, "Assessment 1", NULL, NULL);

    // if failed to create window
    if (window == NULL)
    {
        glfwTerminate();
        exit(EXIT_FAILURE);
    }

    glfwMakeContextCurrent(window); // set window context as the current context
    glfwSwapInterval(1);            // swap buffer interval

    // initialise GLEW
    if (glewInit() != GLEW_OK)
    {
        // if failed to initialise GLEW
        cerr << "GLEW initialisation failed" << endl;
        exit(EXIT_FAILURE);
    }

    // set key callback function
    glfwSetKeyCallback(window, key_callback);
    glfwSetCursorPosCallback(window, cursor_position_callback);

    // use sticky mode to avoid missing state changes from polling
    glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);

    // use mouse to move camera, hence use disable cursor mode
    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);

    // initialise rendering states
    init(window);

    // variables for simple time management
    float lastUpdateTime = glfwGetTime();
    float currentTime = lastUpdateTime;

    // the rendering loop
    while (!glfwWindowShouldClose(window))
    {
        currentTime = glfwGetTime();

        g_camera.update(window);    // update camera

        // only update if more than 0.02 seconds since last update
        if (currentTime - lastUpdateTime > 0.02)
        {
            if (g_enableAnimation) { update_scene(); }      // update the scene
            render_scene();     // render the scene

            glfwSwapBuffers(window);    // swap buffers
            glfwPollEvents();           // poll for events

            lastUpdateTime = currentTime;   // update last update time
        }
    }

    // clean up
    glDeleteProgram(g_shaderProgramID);
    glDeleteBuffers(1, &g_IBO);
    glDeleteBuffers(1, &g_VBO[0]);
    glDeleteBuffers(1, &g_VBO[1]);
    glDeleteVertexArrays(1, &g_VAO[0]);
    glDeleteVertexArrays(1, &g_VAO[1]);

    // close the window and terminate GLFW
    glfwDestroyWindow(window);
    glfwTerminate();

    exit(EXIT_SUCCESS);
}

color.frag

#version 330 core

// interpolated values from the vertex shaders
in vec3 vColor;

// uniform input data
uniform vec3 uAlpha;

// output data
out vec4 fColor;

void main()
{
    // set output color
    fColor = vec4(uAlpha,1);
}