I've created a very simple implementation of a GLFW window. My implementation looks like so
// Include standard headers
#include <stdio.h>
#include <stdlib.h>
// Include glfw for window handling
#include <GLFW/glfw3.h>
int SCREEN_WIDTH = 1280;
int SCREEN_HEIGHT = 720;
GLFWwindow* window;
int main() {
if(!glfwInit()) {
fprintf( stderr, "Failed to initialize GLFW!\n" );
return -1;
}
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_COMPAT_PROFILE);
window = glfwCreateWindow(SCREEN_WIDTH, SCREEN_HEIGHT, "Title", NULL, NULL);
if( !window )
{
fprintf( stderr, "Failed to create window!\n" );
glfwTerminate();
return -1;
}
glClearColor(0.0f, 0.0f, 1.0f, 0.0f);
do {
glfwSwapBuffers(window);
} while(!glfwGetKey(window, GLFW_KEY_ESCAPE));
glfwTerminate();
return 0;
}
It compiles fine, but when I run the application it just "freezes", not showing the correct clear color or anything. It just thinks like crazy (that "thinking"-cursor icon in Windows 7 spins and never stops).
I'm wondering why it freezes like such, does anyone have an idea?
EDIT:
Found the solution to my problem. I was learning from a GLFW2 example, but having the newest version (GLFW3) required me to redo the code some; the thing I didn't realize was that the glSwapBuffers(window) call doens't call glfwPollEvents() by itself, giving me the problem I had.
You're not clearing the buffers, hence the clear colour is not showing through.
You're not adding any kind of delay, so you're swapping empty buffers flat out ("thinking like crazy").
Related
When I started I used the GLFW example code:
#include <GLFW/glfw3.h>
int main(void)
{
GLFWwindow* window;
/* Initialize the library */
if (!glfwInit())
return -1;
/* Create a windowed mode window and its OpenGL context */
window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
if (!window)
{
glfwTerminate();
return -1;
}
/* Make the window's context current */
glfwMakeContextCurrent(window);
/* Loop until the user closes the window */
while (!glfwWindowShouldClose(window))
{
/* Render here */
glClear(GL_COLOR_BUFFER_BIT);
/* Swap front and back buffers */
glfwSwapBuffers(window);
/* Poll for and process events */
glfwPollEvents();
}
glfwTerminate();
return 0;
}
When running this it gives me a black screen titled "Hello world" which is exactly what I want. But by simply adding GLAD:
#include <glad/glad.h>
#include <GLFW/glfw3.h>
...and giving window hints:
//Specify the OpenGL versions we're using
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
Suddenly it tells me the window failed to initialize.
But by simply adding this:
#ifdef __APPLE__
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif
...it allows the window to initialize but crashes when glClear(GL_COLOR_BUFFER_BIT) is called and it gives me the error
'./Voxel\ Game' terminated by signal SIGSEGV (Address boundary error)
I know this because when I remove that line it works, it just doesn't clear the screen.
This is the full code I have now in case the error is somewhere else in there:
#include <iostream>
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#define SCREEN_WIDTH 640
#define SCREEN_HIEGHT 480
int main()
{
GLFWwindow* window;
//Initialize the library
if (!glfwInit())
{
std::cout << "Failed to initalize GLFW" << std::endl;
return -1;
}
//Specify the OpenGL versions we're using
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
#ifdef __APPLE__
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif
//Create a windowed mode window and its OpenGL context
window = glfwCreateWindow(SCREEN_WIDTH, SCREEN_HIEGHT, "Voxel Game", NULL, NULL);
if (!window)
{
std::cout << "Failed create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
//Make the window's context current
glfwMakeContextCurrent(window);
//Loop until the user closes the window
while (!glfwWindowShouldClose(window))
{
//Render here
//glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
//Swap front and back buffers
glfwSwapBuffers(window);
//Poll for and process events
glfwPollEvents();
}
glfwTerminate();
return 0;
}
You are not initializing glad, add gladLoadGL(glfwGetProcAddress); after glfwMakeContextCurrent() and check it returns OK.
In general, there is no OpenGL library apart from some old OpenGL1.1 stuff (in Windows at least), all those GL calls are implemented in the graphics drivers directly, GLAD library just defines a lot of function pointers and wraps them in nicer macros. Then during initialization, it will dynamically load the functions from the drivers present on the machine. Hence the need to generate GLAD for specific OpenGL version.
So if you get segfaults on some GL calls, a good guess is some of those functions were not found, maybe because they are not supported on the HW or because you did not setup GLAD/GLFW correctly.
I'm trying to change the background color in a window generated by OpenGL/GLFW and I'm using a similar code than the one in the GLFW docs. I'm on Ubuntu 20.04 and the window background is always black, no matter the parameters in the glClearColor() function.
I tried this on Windows 10 using VS and it worked perfectly, but on Ubuntu it's not working at all. No error messages are generated.
I also followed The Cherno's Sparky game engine series, and tried encapsulating the glClear() function in a class method, but this didn't change anything.
This is the whole code:
#include <iostream>
#include <GL/gl.h>
#include <GLFW/glfw3.h>
int main(int argc, char *argv[])
{
std::cout << "Hello world!" << std::endl;
if (!glfwInit())
{
// Initialization failed
exit(EXIT_FAILURE);
}
GLFWwindow* window = glfwCreateWindow(640, 480, "My Title", NULL, NULL);
if (!window)
{
// Window or OpenGL context creation failed
std::cout << "Error creating window!" << std::endl;
glfwTerminate();
exit(EXIT_FAILURE);
}
glfwMakeContextCurrent(window);
glfwSwapInterval(1);
glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
while (!glfwWindowShouldClose(window))
{
int width, height;
glfwGetFramebufferSize(window, &width, &height);
glViewport(0, 0, width, height);
glClear(GL_COLOR_BUFFER_BIT);
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwDestroyWindow(window);
glfwTerminate();
exit(EXIT_SUCCESS);
return 0;
}
I'm supposed to get a window with a red background but it's black.
As additional elements, I'm also using CMake to help configuring and building the project (quite overkill I know), and I believe clang is the compiler used for the project. Maybe that influences the result.
You need an appropriate loader after glfwMakeContextCurrent(window).
If you are using glad, you should call gladLoadGL(glfwGetProcAddress) after glfwMakeContextCurrent(window) as the official doc suggests here.
I'm following a fairly simple tutorial and all the files compile, and I am using openGL, glew, and glfw in my current code. The window is not displaying correctly and I don't think it's even displaying. I have my main.cpp:
#include "stdafx.h"
#include "Libs.h"
int main(int argc, char **argv) {
glfwInit();
const int WINDOW_WIDTH = 640;
const int WINDOW_HEIGHT = 480;
int FRAME_BUFFER_WIDTH = 0;
int FRAME_BUFFER_HEIGHT = 0;
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 4);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
GLFWwindow* window = glfwCreateWindow(WINDOW_WIDTH, WINDOW_HEIGHT, "Custom Name", NULL, NULL);
glfwGetFramebufferSize(window, &FRAME_BUFFER_WIDTH, &FRAME_BUFFER_HEIGHT);
glViewport(0, 0, FRAME_BUFFER_WIDTH, FRAME_BUFFER_HEIGHT);
glfwMakeContextCurrent(window);
glewExperimental = GL_TRUE;
if (glfwInit() != GLEW_OK) {
std::cout << "GLFW INIT != GL_OK \n";
glfwTerminate();
}
//Main loop
while (!glfwWindowShouldClose(window)) {
glfwPollEvents();
glClearColor(0.0f, 1.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
glfwSwapBuffers(window);
glFlush();
}
glfwTerminate();
return 1;
}
and my Libs.h
#pragma once
#include <iostream>
#include <glew.h>
#include <glfw3.h>
#include <glm.hpp>
#include <vec2.hpp>
#include <vec3.hpp>
#include <vec4.hpp>
#include <mat4x4.hpp>
#include <gtc/matrix_transform.hpp>
#include <gtc/type_ptr.hpp>
#include <SOIL2.h>
The whole thing compiles just fine and opens without any errors. I can't see any of the console text that I'm displaying (std::cout) as I'm running in visual studio.
The problem is when it opens, the window is displayed like this: Window that's displayed
As you can see, the window is completely blank and there is no green (which it should be). Also, the window name is my solution name and not the one that I gave it ("Custom Name"). Lastly, the icon for the window is a package, which I think means that it's not GL but rather Visual Studio making it. I have no idea why this is happening and no errors are occurring.
If anyone has a possible fix that would be great, thanks.
Fixed:
Pretty simple, I made my project with extra files already there. I needed to make it from an empty project, hopefully this can help somebody in the future.
I'm trying to run my first opengl program in C++, which opens a window, sets a background color, and gives a title, from Terminal on Mac OS X.
The code compiles and links fine. When I run the program the window and title open fine but the background color is always black.
It is my understanding that the function glClearColor sets the background color. However, no matter what parameters I pass to the function, the background color of the window is always black.
If anyone can explain to me what errors I'm making, I would very much appreciate it. Thanks and below is the code:
#include <iostream>
#define GLEW_STATIC
#include <GL/glew.h>
#include <GLFW/glfw3.h>
const GLint WIDTH = 800, HEIGHT = 600;
int main()
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "Learn OpenGL", nullptr, nullptr);
int screenWidth, screenHeight;
glfwGetFramebufferSize(window, &screenWidth, &screenHeight);
if(nullptr == window)
{
std::cout << "Failed to create GLFW window" << '\n';
glfwTerminate();
return -1;
}
glewExperimental = GL_TRUE;
GLenum err=glewInit();
if(err != glewInit())
{
std::cout << "Failed to initialize GLEW" << '\n';
return -1;
}
glViewport(0, 0, screenWidth, screenHeight);
while(!glfwWindowShouldClose(window))
{
glfwPollEvents();
glClearColor(0.2f, 0.2f, 0.9f, 0.5f);
glClear(GL_COLOR_BUFFER_BIT);
glfwSwapBuffers(window);
}
glfwTerminate();
return 0;
}
glClearColor, like all OpenGL functions, works on the current OpenGL context.
You're not setting your window's context as current for your calling thread, so your call to glClearColor does nothing here. Add:
glfwMakeContextCurrent(window);
before your loop.
From glfwMakeContextCurrent docs:
This function makes the OpenGL or OpenGL ES context of the specified window current on the calling thread. A context can only be made current on a single thread at a time and each thread can have only a single current context at a time.
For those of you crazy enough to use pure WIN32 programming:
If your PIXELFORMATDESCRIPTOR has the flag:
PFD_DOUBLEBUFFER
Then all draw calls target the back buffer.
You need to use the windows GDI32 call "SwapBuffers( HDC )" to show the results of your OpenGL calls.
wlgMakeCurrent()
glClearColor( R, G, B, 1.0 ); //: <--Make sure alpha isn't transparent.
glClear( GL_COLOR_BUFFER_BIT )
SwapBuffers( your_window_HDC ); //: from GDI32.dll
To get access to SwapBuffers I use LoadLibrary and GetProcAddress and
put the function pointer in my Win32 functions library.
Also notworthy:
Call SwapBuffers on the same thread as your OpenGL calls.
One more thing. I used multiple threads. So this might be helpful to know:
My window was created in thread "B"
My Context was created in thread "A" using HDC from thread "B"
My openGL draw calls are in thread "A".
I mention this because before I found out about SwapBuffers I thought the problem was because of my multi threading. OpenGL wasn't giving me any errors though, so I had to guess around and experiment and read.
I am trying to create a Blank Window in OpenGL with help of GLFW. below is my code
#include <stdio.h>
#include <stdlib.h>
#include <GL/glew.h>
#include <glfw3.h>
GLFWwindow* window;
#include <glm/glm.hpp>
using namespace glm;
int main( void )
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
window = glfwCreateWindow(800,600,"learnopengl",NULL,NULL);
if (window == NULL)
{
fprintf(stderr,"there is a problem with window creation\n");
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
glewExperimental = GL_TRUE;
if (glewInit() != GLEW_OK)
{
fprintf(stderr,"Failed to initialize GLEW\n");
return -1;
}
int width, height;
glfwGetFramebufferSize(window,&width,&height);
glViewport(0,0,width,height);
while(!glfwWindowShouldClose(window))
{
glfwPollEvents();
glfwSwapBuffers(window);
}
glfwTerminate();
}
but when i try to run the above code instead of a black blank it shows an instance of my current screen in newly created window.
Why do you expect this code to result in a blank window?
As per the spec, the back buffer contents become undefined after you swap the buffers (and initially, they are of course undefined too). As a result, the output you should get is also undefined and basically anything might show up.
Add a glClear(GL_COLOR_BUFFER_BIT) to your render loop if you want some defined output.
I know the answer is late but may concern other people and help them, I ran this code and it's working pretty well, but the problem is not in your code, it is your video card driver, so what is happening ?
OpenGL has what is called "The Default Framebuffer", it is the Framebuffer (the buffer contains what you will see) that OpenGL is created with. It is created along with the OpenGL Context. Like Framebuffer Objects, the default framebuffer is a series of images. Unlike FBOs, one of these images usually represents what you actually see on some part of your screen. in other words the default framebuffer is the buffer used by the operating system to render your desktop and other application's windows, so your application is using the default framebuffer as the framebuffer is not edited by your app, so you may need to clear the framebuffer with some other values, let's say colors. this is your code edited with buffer clearing using colors.
#include <stdio.h>
#include <stdlib.h>
#include <GL/glew.h>
#include <glfw3.h>
GLFWwindow* window;
#include <glm/glm.hpp>
using namespace glm;
int main( void )
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
window = glfwCreateWindow(800,600,"learnopengl",NULL,NULL);
if (window == NULL)
{
fprintf(stderr,"there is a problem with window creation\n");
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
glewExperimental = GL_TRUE;
if (glewInit() != GLEW_OK)
{
fprintf(stderr,"Failed to initialize GLEW\n");
return -1;
}
int width, height;
glfwGetFramebufferSize(window,&width,&height);
glViewport(0,0,width,height);
//this is an added line
glClearColor(1, 1, 1, 1); //the RGBA color we will clear with
while(!glfwWindowShouldClose(window))
{
glfwPollEvents();
//this is an added line
glClear(GL_COLOR_BUFFER_BIT); //the buffer used to clear with
glfwSwapBuffers(window);
}
glfwTerminate();
}
Hope this answer and this code help other people who may have this situation.
for further information about the framebuffer check this link : https://learnopengl.com/Advanced-OpenGL/Framebuffers