opengl cube is not showing properly

Question

I was trying to render the front face of a cube, but it didn't do what I wanted it to. It showed its front face and the bottom face, I don't think there is a problem with the vertices, and I just couldn't figure it out, please help me

this is all the code I have:

#include <iostream>
#include <Windows.h>
#include <SFML\Window.hpp>
#include <SFML\Graphics.hpp>
#include <GL\glew.h>
#include <glm\glm.hpp>
#include <glm\gtc\matrix_transform.hpp>

using namespace std;
using namespace sf;
using namespace glm;

const GLchar* vertexSource =
"#version 430\r\n"
"in vec3 position;"
"in vec3 color;"
"uniform mat4 fullMatrix;"
"out vec3 theColor;"
"void main()"
"{"
"vec4 v = vec4(position, 1.0);"
"gl_Position = fullMatrix * v;"
"theColor = color;"
"}";

const GLchar* fragmentSource =
"#version 430\r\n"
"in vec3 theColor;"
"out vec4 daColor;"
"void main()"
"{"
"    daColor = vec4(theColor, 1.0);"
"}";

int main() {
    Window window(VideoMode(800, 600), "OpenGL", Style::Close);
    window.setFramerateLimit(60);
    glewExperimental = GL_TRUE;
    glewInit();
    glEnable(GL_DEPTH_TEST);

struct vertex {
    vec3 position;
    vec3 color;
};

vertex vert[] = {
    vec3(-1.0f, +1.0f, +1.0f), // 0
    vec3(+1.0f, +0.0f, +0.0f),

    vec3(+1.0f, +1.0f, +1.0f), // 1
    vec3(+0.0f, +1.0f, +0.0f),

    vec3(+1.0f, +1.0f, -1.0f), // 2
    vec3(+0.0f, +0.0f, +1.0f),

    vec3(-1.0f, +1.0f, -1.0f), // 3
    vec3(+1.0f, +1.0f, +1.0f),

    vec3(-1.0f, +1.0f, -1.0f), // 4
    vec3(+1.0f, +0.0f, +1.0f),

    vec3(+1.0f, +1.0f, -1.0f), // 5
    vec3(+0.0f, +0.5f, +0.2f),

    vec3(+1.0f, -1.0f, -1.0f), // 6
    vec3(+0.8f, +0.6f, +0.4f),

    vec3(-1.0f, -1.0f, -1.0f), // 7
    vec3(+0.3f, +1.0f, +0.5f),

    vec3(+1.0f, +1.0f, -1.0f), // 8
    vec3(+0.2f, +0.5f, +0.2f),

    vec3(+1.0f, +1.0f, +1.0f), // 9
    vec3(+0.9f, +0.3f, +0.7f),

    vec3(+1.0f, -1.0f, +1.0f), // 10
    vec3(+0.3f, +0.7f, +1.0f),

    vec3(+1.0f, -1.0f, -1.0f), // 11
    vec3(+0.5f, +0.7f, +0.5f),

    vec3(-1.0f, +1.0f, +1.0f), // 12
    vec3(+0.7f, +0.8f, +0.2f),

    vec3(-1.0f, +1.0f, -1.0f), // 13
    vec3(+0.5f, +0.7f, +0.3f),

    vec3(-1.0f, -1.0f, -1.0f), // 14
    vec3(+0.4f, +0.7f, +0.7f),

    vec3(-1.0f, -1.0f, +1.0f), // 15
    vec3(+0.2f, +0.5f, +1.0f),

    vec3(+1.0f, +1.0f, +1.0f), // 16
    vec3(+0.6f, +1.0f, +0.7f),

    vec3(-1.0f, +1.0f, +1.0f), // 17
    vec3(+0.6f, +0.4f, +0.8f),

    vec3(-1.0f, -1.0f, +1.0f), // 18
    vec3(+0.2f, +0.8f, +0.7f),

    vec3(+1.0f, -1.0f, +1.0f), // 19
    vec3(+0.2f, +0.7f, +1.0f),

    vec3(+1.0f, -1.0f, -1.0f), // 20
    vec3(+0.8f, +0.3f, +0.7f),

    vec3(-1.0f, -1.0f, -1.0f), // 21
    vec3(+0.8f, +0.9f, +0.5f),

    vec3(-1.0f, -1.0f, +1.0f), // 22
    vec3(+0.5f, +0.8f, +0.5f),

    vec3(+1.0f, -1.0f, +1.0f), // 23
    vec3(+0.9f, +1.0f, +0.2f),
};

GLuint numVertices = sizeof(vert) / sizeof(*vert);

GLuint vboBuffer;
glGenBuffers(1, &vboBuffer);
glBindBuffer(GL_ARRAY_BUFFER, vboBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(vert), vert, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 6, 0);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 6, (void*)(sizeof(float) * 3));

GLushort indi[] = {
    0,   1,  2,  0,  2,  3, // Top
    4,   5,  6,  4,  6,  7, // Front
    8,   9, 10,  8, 10, 11, // Right
    12, 13, 14, 12, 14, 15, // Left
    16, 17, 18, 16, 18, 19, // Back
    20, 22, 21, 20, 23, 22, // Bottom
};

GLuint numIndices = sizeof(indi) / sizeof(*indi);

GLuint indiBuffer;
glGenBuffers(1, &indiBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indiBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indi), indi, GL_STATIC_DRAW);

GLuint vertexShaderID = glCreateShader(GL_VERTEX_SHADER);
GLuint fragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);
GLuint programID = glCreateProgram();

glShaderSource(vertexShaderID, 1, &vertexSource, 0);
glShaderSource(fragmentShaderID, 1, &fragmentSource, 0);
glCompileShader(vertexShaderID);
glCompileShader(fragmentShaderID);

glAttachShader(programID, vertexShaderID);
glAttachShader(programID, fragmentShaderID);
glLinkProgram(programID);
glUseProgram(programID);

bool running = true;
while (running)
{
    Event event;
    while (window.pollEvent(event))
    {
        if (event.type == Event::Closed) {
            running = false;
        }
        else if (event.type == Event::KeyPressed && event.key.code == Keyboard::Escape) {
            running = false;
        }
    }

    glClearColor(0, 0, 0, 1);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    mat4 transformMatrix = translate(mat4(), vec3(0.0f, 0.0f, -3.0f));
    mat4 projectionMatrix = perspective(45.0f, (float)800 / 600, 0.1f, 10.0f);
    mat4 fullMatrix = projectionMatrix * transformMatrix;

    GLint fullLocation = glGetUniformLocation(programID, "fullMatrix");

    glUniformMatrix4fv(fullLocation, 1, GL_FALSE, &fullMatrix[0][0]);

    glDrawElements(GL_TRIANGLES, numIndices, GL_UNSIGNED_SHORT, 0);

    window.display();
}
}

it shows this image

but I don't want the bottom face to show up

Answer 1

Since the depth-test already gets enabled ( glEnable(GL_DEPTH_TEST ), but is obviously not working, it seems that the window does not have a depth buffer. From the SFML documentation it looks as if one has to request that manually:

sf::ContextSettings settings;
settings.depthBits = 24;          //<-- This is the important line
settings.stencilBits = 8;
settings.antialiasingLevel = 4;
settings.majorVersion = 3;
settings.minorVersion = 0;

sf::Window window(sf::VideoMode(800, 600), "OpenGL", sf::Style::Default, settings);

You might have to adapt the OpenGL version etc. to your needs, but make sure not to set depthBits to zero.