I am trying to draw a simple cube in OpenGL and GLFW.
In the code below, I can draw the cube, but it just appears as a simple rectangle. What is happening here?
#if defined(_WIN32) || defined(_WIN64)
#include <windows.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <fstream>
#define GLEW_STATIC
#include <GL/glew.h>
#include <GL/gl.h>
#include <GLFW/glfw3.h>
const char* gameTitle = "TEST";
GLFWwindow* window;
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, 0, 0, 0, 0, 1, 0, 1, 1, 0, 1, 0,
1, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0,
0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0,
0, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0,
0, 0, 0, 0, 1, 0, 1, 1, 0, 1, 0, 0,
0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1
};
static void controls(GLFWwindow* window, int key, int scancode, int action, int mods)
{
if(action == GLFW_PRESS)
if(key == GLFW_KEY_ESCAPE)
glfwSetWindowShouldClose(window, GL_TRUE);
}
bool initWindow(const int resX, const int resY)
{
if(!glfwInit())
{
fprintf(stderr, "Failed to initialize GLFW\n");
return false;
}
glfwWindowHint(GLFW_SAMPLES, 4); // 4x antialiasing
// Open a window and create its OpenGL context
window = glfwCreateWindow(resX, resY, gameTitle, NULL, NULL);
if(window == NULL)
{
fprintf(stderr, "Failed to open GLFW window.\n");
glfwTerminate();
return false;
}
glfwMakeContextCurrent(window);
glfwSetKeyCallback(window, controls);
// Get info of GPU and supported OpenGL version
printf("Renderer: %s\n", glGetString(GL_RENDERER));
printf("OpenGL version supported %s\n", glGetString(GL_VERSION));
glEnable(GL_DEPTH_TEST); // Depth Testing
glDepthFunc(GL_LEQUAL);
glDisable(GL_CULL_FACE);
glCullFace(GL_BACK);
return true;
}
static void drawCube()
{
static float alpha = 0;
glMatrixMode(GL_PROJECTION_MATRIX);
glLoadIdentity();
glTranslatef(0,0,-2);
glMatrixMode(GL_MODELVIEW_MATRIX);
//attempt to rotate cube
//glRotatef(alpha, 1, 0, 0);
/* We have a color array and a vertex array */
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glVertexPointer(3, GL_FLOAT, 0, vertices);
glColorPointer(3, GL_FLOAT, 0, colors);
/* Send data : 24 vertices */
glDrawArrays(GL_QUADS, 0, 24);
/* Cleanup states */
glDisableClientState(GL_COLOR_ARRAY);
glDisableClientState(GL_VERTEX_ARRAY);
alpha += 0.1;
}
static void display()
{
glClearColor(0.0, 0.8, 0.3, 1.0);
while(!glfwWindowShouldClose(window))
{
// Draw stuff
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
drawCube();
// Update Screen
//glFlush();
glfwSwapBuffers(window);
// Check for any input, or window movement
glfwPollEvents();
// Scale to window size
GLint windowWidth, windowHeight;
glfwGetWindowSize(window, &windowWidth, &windowHeight);
glViewport(0, 0, windowWidth, windowHeight);
}
}
int main(int argc, char** argv)
{
if(initWindow(1024, 620))
{
display();
}
printf("Goodbye!\n");
glfwDestroyWindow(window);
glfwTerminate();
return 0;
}
I've tried "glTransformf(0,0,-10);", but if I do anything less than -2, than the cube disappears. at -2, the front face side appears. at the default position of 0, I can see the back side of the cube.
Also, when I try to rotate it, all that shows up is a rectangle moving from the top of the window, to the bottom. Seems very odd.
Why is the program is behaving this way?
drawCube(), single responsibility principle and all that.c-prefixed versions (stdio.h -> cstdio) of the C headers. Use those instead.All together:
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <cstdio>
void controls(GLFWwindow* window, int key, int scancode, int action, int mods)
{
if(action == GLFW_PRESS)
if(key == GLFW_KEY_ESCAPE)
glfwSetWindowShouldClose(window, GL_TRUE);
}
GLFWwindow* initWindow(const int resX, const int resY)
{
if(!glfwInit())
{
fprintf(stderr, "Failed to initialize GLFW\n");
return NULL;
}
glfwWindowHint(GLFW_SAMPLES, 4); // 4x antialiasing
// Open a window and create its OpenGL context
GLFWwindow* window = glfwCreateWindow(resX, resY, "TEST", NULL, NULL);
if(window == NULL)
{
fprintf(stderr, "Failed to open GLFW window.\n");
glfwTerminate();
return NULL;
}
glfwMakeContextCurrent(window);
glfwSetKeyCallback(window, controls);
// Get info of GPU and supported OpenGL version
printf("Renderer: %s\n", glGetString(GL_RENDERER));
printf("OpenGL version supported %s\n", glGetString(GL_VERSION));
glEnable(GL_DEPTH_TEST); // Depth Testing
glDepthFunc(GL_LEQUAL);
glDisable(GL_CULL_FACE);
glCullFace(GL_BACK);
return window;
}
void drawCube()
{
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, 0, 0, 0, 0, 1, 0, 1, 1, 0, 1, 0,
1, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0,
0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0,
0, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0,
0, 0, 0, 0, 1, 0, 1, 1, 0, 1, 0, 0,
0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1
};
static float alpha = 0;
//attempt to rotate cube
glRotatef(alpha, 0, 1, 0);
/* We have a color array and a vertex array */
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glVertexPointer(3, GL_FLOAT, 0, vertices);
glColorPointer(3, GL_FLOAT, 0, colors);
/* Send data : 24 vertices */
glDrawArrays(GL_QUADS, 0, 24);
/* Cleanup states */
glDisableClientState(GL_COLOR_ARRAY);
glDisableClientState(GL_VERTEX_ARRAY);
alpha += 1;
}
void display( GLFWwindow* window )
{
while(!glfwWindowShouldClose(window))
{
// Scale to window size
GLint windowWidth, windowHeight;
glfwGetWindowSize(window, &windowWidth, &windowHeight);
glViewport(0, 0, windowWidth, windowHeight);
// Draw stuff
glClearColor(0.0, 0.8, 0.3, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION_MATRIX);
glLoadIdentity();
gluPerspective( 60, (double)windowWidth / (double)windowHeight, 0.1, 100 );
glMatrixMode(GL_MODELVIEW_MATRIX);
glTranslatef(0,0,-5);
drawCube();
// Update Screen
glfwSwapBuffers(window);
// Check for any input, or window movement
glfwPollEvents();
}
}
int main(int argc, char** argv)
{
GLFWwindow* window = initWindow(1024, 620);
if( NULL != window )
{
display( window );
}
glfwDestroyWindow(window);
glfwTerminate();
return 0;
}