So, 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?
I've tried "glTransformf(0,0,-10);", but if I do anything less than -2, than the cube dissappears. 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.
Can anyone help me find out why the program is behaving this way?
#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;
}
c and is compiled along with all other examples when you build GLFW. If you built GLFW from the source package then you already have this as simple.exe on Windows, simple on Linux or simple.
GLFW provides a thin, multi-platform abstraction layer, primarily for applications whose sole graphics output is through OpenGL, OpenGL ES or Vulkan.
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;
}
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