C++ OpenGL I can't see a cube on the screen - c++

Question

I can't see a cube on the screen.I located it with glTranslatef. I got it to stop somewhere with LoadIdentity. I wanted to get a camera by changing the Matrix Modes, but the cube does not appear.
Code:
#include <Windows.h>
#include <gl/GL.h>
#include <gl/GLU.h>
#include <GLFW/glfw3.h>
#include <cstdio>
int width = 1280;
int height = 720;
GLfloat vertices[] = {
-1, -1, -1, -1, -1, 1, -1, 1, 1, -1, 1, -1,
1, -1, -1, 1, -1, 1, 1, 1, 1, 1, 1, -1,
-1, -1, -1, -1, -1, 1, 1, -1, 1, 1, -1, -1,
-1, 1, -1, -1, 1, 1, 1, 1, 1, 1, 1, -1,
-1, -1, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1,
-1, -1, 1, -1, 1, 1, 1, 1, 1, 1, -1, 1
};
GLfloat colors[] =
{
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0,
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0,
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0,
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0,
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0,
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0
};
void keyboard(GLFWwindow* window, int key, int scancode, int action, int mods) {
if (action == GLFW_PRESS)
if (key == GLFW_KEY_ESCAPE)
glfwSetWindowShouldClose(window, GL_TRUE);
}
void drawCube() {
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glVertexPointer(3, GL_FLOAT, 0, vertices);
glColorPointer(3, GL_FLOAT, 0, colors);
glDrawArrays(GL_QUADS, 0, 24);
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_COLOR_ARRAY);
}
int main(void)
{
GLFWwindow* window;
/* Initialize the library */
if (!glfwInit())
return -1;
/* Create a windowed mode window and its OpenGL context */
window = glfwCreateWindow(width, height, "C++ OpenGL Test Area", NULL, NULL);
if (!window)
{
glfwTerminate();
return -1;
}
/* Make the window's context current */
glfwMakeContextCurrent(window);
glfwSetKeyCallback(window, keyboard);
glEnable(GL_DEPTH_TEST);
/* Loop until the user closes the window */
while (!glfwWindowShouldClose(window))
{
glViewport(0, 0, width, height);
/* Render here */
glClearColor(0.0, 192/256, 1, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluLookAt(1, 1, 1, 0, 0, 0, 0, 1, 0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0, 0, 5);
drawCube();
glFlush();
/* Swap front and back buffers */
glfwSwapBuffers(window);
/* Poll for and process events */
glfwPollEvents();
}
glfwTerminate();
return 0;
}
I thought it was because I couldn't draw the cube. I checked the codes again, but there is no problem drawing the cube.

Answer 1

The cube is not in the viewing volume. If you do not specify a projection matrix, the viewing volume is a unique cube around the camera position, aligned along the line of sight. Any geometry that is not in the viewing volume is clipped. You must set up a projection matrix. The projection matrix defines the volume in the scene that is projected onto the viewport. An orthographic projection matrix can be set with glOrtho. A perspective projection matrix can be set with glFrustum or gluPerspective. The perspective projection matrix defines a Viewing frustum. e.g.:
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
float aspect = (float)width / (float)height;
gluPerspective(90.0, aspect, 0.1, 10.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(4, 4, 4, 0, 0, 0, 0, 1, 0);
drawCube();