我正在尝试在 Mac 上测试 glfw3。我无法构建一个简单的项目,因为我无法链接到 OpenGL。
目录结构
├── CMakeLists.txt
├── OpenGL
│ ├── Application.cpp
│ ├── CMakeLists.txt
│ └── dependencies
│ └── GLFW
│ ├── include
│ │ └── GLFW
│ │ ├── glfw3.h
│ │ └── glfw3native.h
│ ├── lib
│ │ └── libglfw3.a
│ └── src
└── bin
CMakeList.txt
顶级 CMakeList.txt
cmake_minimum_required(VERSION 3.11)
set(CMAKE_CXX_STANDARD 17)
set(EXECUTABLE_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/bin)
add_subdirectory(OpenGL)
嵌套 CMakeList.txt
cmake_minimum_required(VERSION 3.11)
project(OpenGL)
find_package(OpenGL REQUIRED)
add_executable(OpenGL Application.cpp)
target_include_directories(OpenGL PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/dependencies/GLFW/include)
target_link_libraries(OpenGL ${OPENGL_LIBRARIES} ${CMAKE_CURRENT_SOURCE_DIR}/dependencies/GLFW/lib/libglfw3.a)
Applicatin.cpp(从glfw.org直接带到这里)
#include <iostream>
#include <GLFW/glfw3.h>
int main()
{
GLFWwindow* window;
/* Initialize the library */
if (!glfwInit())
return -1;
/* Create a windowed mode window and its OpenGL context */
window = glfwCreateWindow(640, 480, "Hello World", nullptr, nullptr);
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); <-- this line throws an error
/* Swap front and back buffers */
glfwSwapBuffers(window);
/* Poll for and process events */
glfwPollEvents();
}
glfwTerminate();
return 0;
}
错误信息
make[3]: *** No rule to make target '../OpenGL/dependencies/GLFW/include/lib/libglfw3.a', needed by '../bin/OpenGL'. Stop.
make[3]: *** Waiting for unfinished jobs....
[ 50%] Building CXX object OpenGL/CMakeFiles/OpenGL.dir/Application.cpp.o
/Users/dblock/CLionProjects/OpenGL/OpenGL/Application.cpp:27:17: error: use of undeclared identifier 'GL_COLOR_BUFFER_BIT'
glClear(GL_COLOR_BUFFER_BIT);
^
1 error generated.
make[3]: *** [OpenGL/CMakeFiles/OpenGL.dir/build.make:63: OpenGL/CMakeFiles/OpenGL.dir/Application.cpp.o] Error 1
make[2]: *** [CMakeFiles/Makefile2:86: OpenGL/CMakeFiles/OpenGL.dir/all] Error 2
make[1]: *** [CMakeFiles/Makefile2:98: OpenGL/CMakeFiles/OpenGL.dir/rule] Error 2
make: *** [Makefile:118: OpenGL] Error 2
我的 IDE (CLion) 说明如下
Can't resolve variable 'glClear'
Can't resolve variable 'GL_COLOR_BUFFER_BIT'
请让我知道我哪里出错了。
编辑
我添加了#import,现在我收到一个新错误
/usr/local/Cellar/cmake/3.11.1/bin/cmake --build /Users/dblock/CLionProjects/OpenGL/cmake-build-debug --target OpenGL -- -j 4
make[3]: *** No rule to make target '../OpenGL/dependencies/GLFW/include/lib/libglfw3.a', needed by '../bin/OpenGL'. Stop.
make[2]: *** [CMakeFiles/Makefile2:86: OpenGL/CMakeFiles/OpenGL.dir/all] Error 2
make[1]: *** [CMakeFiles/Makefile2:98: OpenGL/CMakeFiles/OpenGL.dir/rule] Error 2
make: *** [Makefile:118: OpenGL] Error 2
解决方案
#include <OpenGL/gl.h> //<-- add this included to main.cpp fixed my issue
IDE 清楚地表明没有找到声明glClear
和GL_COLOR_BUFFER_BIT
由于 OpenGL 是一种标准/规范,因此驱动程序制造商将规范实现到特定显卡支持的驱动程序。由于OpenGL驱动有很多不同的版本,其大部分函数的位置在编译时是未知的,需要在运行时查询。然后开发人员的任务是检索他/她需要的函数的位置并将它们存储在函数指针中以供以后使用。
您需要声明 OpenGL 函数的标头和加载这些函数的加载器。值得庆幸的是,也有一些用于此目的的库,其中 GLAD 是一个流行且最新的库。
生成 GLAD 加载器/标题 - http://glad.dav1d.de。
更新目录结构:
├── CMakeLists.txt
├── OpenGL
│ ├── Application.cpp
│ ├── CMakeLists.txt
│ ├── glad.c
│ └── dependencies
│ ├── GLFW
│ │ └── ...
│ ├── glad
│ │ └── glad.h
│ └── KHR
│ └── khrplatform.h
└── bin
更新嵌套的 CMakeList.txt:
set(SOURCES Application.cpp glad.c)
add_executable(OpenGL ${SOURCES})
target_include_directories(OpenGL PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/dependencies)
更新 Applicatin.cpp:
#include <glad/glad.h>
#include <GLFW/glfw3.h>
...
glfwMakeContextCurrent(window);
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
// Failed to create GLFW window
glfwTerminate();
return -1;
}
// now you can use OpenGL functions
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