在见过各类使用OpenGL制作的看起来很酷的效果后，愈发的萌生了想要学习的想法。

本系列基于LearnOpenGL-CN教程，记录整体的学习过程与遇到的各类问题。

环境配置

虽然教程里使用的是Visual Studio来搭建OpenGL环境，但是我实在是不想用这么重量级的应用，因为我的目标是学习OpenGL，因此选用了Visual Studio Code来作为开发环境。

配置C/C++环境

由于之前很少写过C/C++，所有理所当然的环境也要从0开始搭建。还在大学还残留了一丝记忆，还记得MingGW，CMake这些。

下载配置MingGW环境

MingGw
安装好后配置相应的环境变量，可以使用以下命名检查配置是否成功

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gcc -v

配置GLFW和GLAD

GLFW就直接使用预编译好的就行: GLFW下载
GLAD需要配置对应的版本来生成头文件和实现：GLAD
这部分可以完全参照LearnOpenGL文档里的教程：

打开GLAD的在线服务，将语言(Language)设置为C/C++，在API选项中，选择3.3以上的OpenGL(gl)版本（我们的教程中将使用3.3版本，但更新的版本也能用）。之后将模式(Profile)设置为Core，并且保证选中了生成加载器(Generate a loader)选项。现在可以先（暂时）忽略扩展(Extensions)中的内容。都选择完之后，点击生成(Generate)按钮来生成库文件。

搭建OpenGL C/C++项目

我推荐将上述下载的内容都整和到同一个文件夹下，比如

  • LearnOpenGL
    • glfw-3.4.bin.WIN64 (GLFW依赖)
    • mingw64
    • Projects (项目文件夹)

配置C/C++项目

现在开始着手VS Code的配置，首先安装以下扩展：

然后我们可以新建个项目，按下Ctrl + Shift + P运行Create C++ Projects来快速构建CMake项目。
整体项目结构如下：
项目结构
我们可以直接运行检查是否输出Hello world!来确认项目是否构建成功

添加GLFW,GLAD依赖

  1. 将glfw-3.4.bin.WIN64里的include/GLFW复制到项目的include目录下，lib-mingw-w64同样的移到项目的lib目录下

    当然，你也可以手动配置include/lib路径到glfw来避免复制文件

  2. 将GLAD生成的zip里的include和src整体复制到项目中，目录都是对应的。

由于默认是C++项目，所有我们还需要调整Makefile文件来识别.c文件。

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# define the C source files
SOURCES		:= $(wildcard $(patsubst %,%/*.cpp, $(SOURCEDIRS))) $(wildcard $(patsubst %,%/*.c, $(SOURCEDIRS)))

# define the C object files
OBJECTS		:= $(patsubst %.cpp,%.o,$(patsubst %.c,%.o,$(SOURCES)))

.c.o:
	$(CXX) $(INCLUDES) -c -MMD $< -o $@

最后Makefile文件如下：

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#
# 'make'        build executable file 'main'
# 'make clean'  removes all .o and executable files
#

# define the Cpp compiler to use
CXX = g++

# define any compile-time flags
CXXFLAGS	:= -std=c++17 -Wall -Wextra -g

# define library paths in addition to /usr/lib
#   if I wanted to include libraries not in /usr/lib I'd specify
#   their path using -Lpath, something like:
LFLAGS := -lglfw3 -lopengl32 -lgdi32

# define output directory
OUTPUT	:= output

# define source directory
SRC		:= src

# define include directory
INCLUDE	:= include

# define lib directory
LIB		:= lib

ifeq ($(OS),Windows_NT)
MAIN	:= main.exe
SOURCEDIRS	:= $(SRC)
INCLUDEDIRS	:= $(INCLUDE)
LIBDIRS		:= $(LIB)
FIXPATH = $(subst /,\,$1)
RM			:= del /q /f
MD	:= mkdir
else
MAIN	:= main
SOURCEDIRS	:= $(shell find $(SRC) -type d)
INCLUDEDIRS	:= $(shell find $(INCLUDE) -type d)
LIBDIRS		:= $(shell find $(LIB) -type d)
FIXPATH = $1
RM = rm -f
MD	:= mkdir -p
endif

# define any directories containing header files other than /usr/include
INCLUDES	:= $(patsubst %,-I%, $(INCLUDEDIRS:%/=%))

# define the C libs
LIBS		:= $(patsubst %,-L%, $(LIBDIRS:%/=%))

# define the C source files
SOURCES		:= $(wildcard $(patsubst %,%/*.cpp, $(SOURCEDIRS))) $(wildcard $(patsubst %,%/*.c, $(SOURCEDIRS)))

# define the C object files
OBJECTS		:= $(patsubst %.cpp,%.o,$(patsubst %.c,%.o,$(SOURCES)))

# define the dependency output files
DEPS		:= $(OBJECTS:.o=.d)

#
# The following part of the makefile is generic; it can be used to
# build any executable just by changing the definitions above and by
# deleting dependencies appended to the file from 'make depend'
#

OUTPUTMAIN	:= $(call FIXPATH,$(OUTPUT)/$(MAIN))

all: $(OUTPUT) $(MAIN)
	@echo Executing 'all' complete!

$(OUTPUT):
	$(MD) $(OUTPUT)

$(MAIN): $(OBJECTS)
	$(CXX) $(CXXFLAGS) $(INCLUDES) -o $(OUTPUTMAIN) $(OBJECTS) $(LFLAGS) $(LIBS)

# include all .d files
-include $(DEPS)

# this is a suffix replacement rule for building .o's and .d's from .c's
# it uses automatic variables $<: the name of the prerequisite of
# the rule(a .c file) and $@: the name of the target of the rule (a .o file)
# -MMD generates dependency output files same name as the .o file
# (see the gnu make manual section about automatic variables)
.cpp.o:
	$(CXX) $(CXXFLAGS) $(INCLUDES) -c -MMD $<  -o $@
.c.o:
	$(CXX) $(INCLUDES) -c -MMD $< -o $@

.PHONY: clean
clean:
	$(RM) $(OUTPUTMAIN)
	$(RM) $(call FIXPATH,$(OBJECTS))
	$(RM) $(call FIXPATH,$(DEPS))
	@echo Cleanup complete!

run: all
	./$(OUTPUTMAIN)
	@echo Executing 'run: all' complete!

现在我们可以测试以下，将main.cpp文件修改为OpenGL示例代码：

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#include <glad/glad.h>
#include <GLFW/glfw3.h>

#include <iostream>

void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow *window);

// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

int main()
{
    // glfw: initialize and configure
    // ------------------------------
    glfwInit();
    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

    // glfw window creation
    // --------------------
    GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
    if (window == NULL)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    // glad: load all OpenGL function pointers
    // ---------------------------------------
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }    

    // render loop
    // -----------
    while (!glfwWindowShouldClose(window))
    {
        // input
        // -----
        processInput(window);

        // render
        // ------
        glClearColor(0.6f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        // -------------------------------------------------------------------------------
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    // glfw: terminate, clearing all previously allocated GLFW resources.
    // ------------------------------------------------------------------
    glfwTerminate();
    return 0;
}

// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
void processInput(GLFWwindow *window)
{
    if(glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);
}

// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    // make sure the viewport matches the new window dimensions; note that width and 
    // height will be significantly larger than specified on retina displays.
    glViewport(0, 0, width, height);
}

直接运行，应该会展示一个窗口，最终项目结构与示例如下图：
运行

示例源码

以上示例项目源码已同步到Github: LearnOpenGL Github，如果有其他的问题可以尝试直接clone下来。

许可协议

本文采用 署名-非商业性使用-相同方式共享 4.0 国际 许可协议，转载请注明出处。

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