c++ - OpenGL glClearColor 总是黑屏

Question

我正在尝试在 C++ 中运行我的第一个 opengl 程序，它会在 Mac OS X 上的终端打开一个窗口、设置背景颜色并给出标题。

代码可以正常编译和链接。当我运行该程序时，窗口和标题可以正常打开，但背景颜色始终为黑色。

据我了解，函数 glClearColor 设置背景色。但是，无论我向函数传递什么参数，窗口的背景颜色始终是黑色。

如果有人能向我解释我所犯的错误，我将不胜感激。谢谢，下面是代码:

#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;
}

Answer 1

glClearColor，与所有 OpenGL 函数一样，在当前 OpenGL 上下文中工作。

您没有将窗口的上下文设置为调用线程的当前上下文，因此您对 glClearColor 的调用在这里不执行任何操作。添加:

glfwMakeContextCurrent(window);

在你的循环之前。

来自 glfwMakeContextCurrent文档:

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.