文章目录
1、简介
1.1 OpenGL简介
Linux 系统中的 OpenGL 是一个跨语言、跨平台的应用程序编程接口(API),用于渲染2D和3D矢量图形。
这里显示 OpenGL 的版本信息:
glxinfo| grep version
glxinfo:这是一个用于查询关于 OpenGL 图形系统的信息的命令行工具。它提供了关于图形硬件、驱动程序以及支持的 OpenGL 扩展的详细信息。
grep:这是一个文本搜索工具,用于搜索文本文件或输出中匹配特定模式的行。在这里,它用于搜索包含“version”这个词的行。
glxinfo没有安装,执行如下命令进行安装:
sudo apt install mesa-utils
安装成功,继续上面的glxinfo命令如下:
使用 glxgears 命令来测试 OpenGL 的性能,它是一个简单的 OpenGL 程序,显示旋转的齿轮,可以用来测试图形硬件的渲染能力。
glxgears
eglinfo:类似于 glxinfo,但是用于查询有关 EGL (嵌入式系统图形接口) 的信息。
eglinfo
1.2 glew简介
GLEW(OpenGL Extension Wrangler Library)是一个跨平台的开源 C/C++ 扩展加载库,用于确定目标平台支持哪些 OpenGL 扩展。它提供了高效的运行时机制,并且已经过多种操作系统的测试,包括 Windows、Linux、Mac OS X、FreeBSD、Irix 和 Solaris。GLEW 使得 OpenGL 核心和扩展功能的声明都包含在单个头文件中,简化了 OpenGL 扩展的使用。
输入glew官方网址:
https://glew.sourceforge.net/
2、安装glew
2.1 命令安装glew
sudo apt-cache search glew
# sudo apt-get install libglew-dbg libglew-dev libglew1.13 libglewmx-dbg libglewmx-dev libglewmx1.13 glew-utils
sudo apt-get -y install glew-utils
在 Linux 系统中安装 GLEW 可以通过包管理器进行。例如,在基于 Debian 的系统(如 Ubuntu)中,可以使用以下命令安装 GLEW:
# sudo apt install libglew2.1 libglew-dev
sudo apt-get install libglew-dev
# /usr/lib/x86_64-linux-gnu/libGLEW.so
这将安装 GLEW 的开发文件,包括库文件和头文件。安装后,你可以在项目中包含 GLEW 头文件,并链接到 GLEW 库以使用 OpenGL 扩展。
如果通过cmake编译,在CMakeLists.txt添加如下代码:
find_package(GLEW REQUIRED)
target_link_libraries(untitled1 GLEW::GLEW)
- 完整的CMakeLists.txt:
cmake_minimum_required(VERSION 3.16)
project(untitled1 LANGUAGES CXX)
set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
find_package(GLEW REQUIRED)
add_executable(untitled1
main.cpp
)
target_link_libraries(untitled1 GLEW::GLEW)
include(GNUInstallDirs)
install(TARGETS untitled1
LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
)
- main.cpp:
#include <GL/glew.h>
#include <iostream>
int main(int argc, char *argv[])
{
std::cout << "hello yxy" << std::endl;
// 初始化 GLEW
glewExperimental = GL_TRUE;
if (glewInit() != GLEW_OK) {
std::cout << "glew init failed." << std::endl;
}
else {
std::cout << "glew init ok." << std::endl;
}
return 0;
}
编译测试项目代码如下:
再给一个glew测试的例子:
- main.cpp:
#include <GL/glew.h>
#include <stdio.h>
#include <stdlib.h>
#define S(x) SS(x)
#define SS(x) #x
int main(int argc, char* argv[]) {
printf("GLEW CMake test, %s build\n",
S(GLEW_CMAKE_TEST_CONFIG));
printf("-- linked to %s which is %s\n",
S(GLEW_CMAKE_TEST_TARGET_FILE_NAME),
S(GLEW_CMAKE_TEST_TARGET_TYPE));
const GLubyte* v = glewGetString(GLEW_VERSION);
if(v) {
printf("-- glewGetString(GLEW_VERSION) returns %s\n-- test passed.\n", v);
return EXIT_SUCCESS;
} else {
printf("-- glewGetString(GLEW_VERSION) returns NULL\n-- test failed.\n");
return EXIT_FAILURE;
}
}
卸载libglew-dev库后运行如下:
sudo apt autoremove libglew-dev
再编译上面的测试项目代码如下:
2.2 直接代码安装glew
如果你需要从源代码编译 GLEW,可以访问 GLEW 的官方网站或其 GitHub 仓库获取源代码。编译 GLEW 通常需要安装一些构建工具,如 make、gcc、git 等。在 Linux 系统上,可以使用以下命令安装这些工具:
sudo apt-get install build-essential libxmu-dev libxi-dev libgl-dev
GLEW(OpenGL Extension Wrangler)的官方网站是 http://glew.sourceforge.net/,可以在这个网站上下载GLEW的源代码并进行安装。
wget下载源码如下:
wget https://jaist.dl.sourceforge.net/project/glew/glew/2.1.0/glew-2.1.0.tgz
或者使用curl命令下载:
curl https://jaist.dl.sourceforge.net/project/glew/glew/2.1.0/glew-2.1.0.tgz -o glew-2.1.0.tgz
执行如下命令进行解压和编译。
tar -zxvf glew-2.1.0.tgz
cd glew-2.1.0
#cmake ../cmake -DCMAKE_INSTALL_PREFIX=./install
make
sudo make install
解压glew-2.1.0.tgz如下:
通过make编译源代码如下:
安装编译后文件到系统目录:
sudo make install
make clean
查看一下本机上glew被安装的文件夹:
find / -name libGLEW.so
使用如下代码,静态链接到特定位置的自定义编译 GLEW 库:
#GLEW libraries
add_library(glew_static STATIC IMPORTED)
# add_library(glew_static SHARED IMPORTED)
set_target_properties(glew_static PROPERTIES
IMPORTED_LOCATION /usr/lib64/libGLEW.a)
target_link_libraries(testglew glew_static)
也可以将它与共享库一起使用,只需从 add_library 中删除 STATIC 关键字。
如果通过cmake编译,在CMakeLists.txt添加如下代码:
- CMakeLists.txt
cmake_minimum_required(VERSION 3.16)
project(untitled1 LANGUAGES CXX)
set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
#####################
# glew
add_library(glew_static STATIC IMPORTED)
set_target_properties(glew_static PROPERTIES
IMPORTED_LOCATION /usr/lib64/libGLEW.a)
#####################
# opengl
find_package(OpenGL REQUIRED)
add_executable(untitled1
main.cpp
)
target_link_libraries(untitled1 glew_static OpenGL::GL)
include(GNUInstallDirs)
install(TARGETS untitled1
LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
)
- main.cpp
#include <GL/glew.h>
#include <iostream>
int main(int argc, char *argv[])
{
std::cout << "hello yxy" << std::endl;
// 初始化 GLEW
glewExperimental = GL_TRUE;
if (glewInit() != GLEW_OK) {
std::cout << "glew init failed." << std::endl;
}
else {
std::cout << "glew init ok." << std::endl;
}
return 0;
}
编译测试项目如下:
2.3 cmake代码安装glew
tar -zxvf glew-2.1.0.tgz
cd glew-2.1.0
cd build
mkdir linux
cd linux
cmake ../cmake -DCMAKE_INSTALL_PREFIX=./install
# cmake ../cmake -DCMAKE_INSTALL_PREFIX=/usr/local/thirdparty
make
make install
执行make install后安装到当前文件夹的install子文件夹里:
3、测试glew
3.1 测试glew+freeglut
- CMakeLists.txt:
cmake_minimum_required(VERSION 3.16)
project(testglew LANGUAGES CXX)
set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
#####################
# glew
find_package(GLEW REQUIRED)
#####################
# glut
find_package(OpenGL REQUIRED)
find_package(GLUT REQUIRED)
include_directories(${OPENGL_INCLUDE_DIRS})
include_directories(${GLUT_INCLUDE_DIRS})
add_executable(testglew
main.cpp
)
target_link_libraries(testglew
GLEW::GLEW
${OPENGL_LIBRARIES} ${GLUT_LIBRARIES}
)
include(GNUInstallDirs)
install(TARGETS testglew
LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
)
- main.cpp
#include <iostream>
// GLEW
#define GLEW_STATIC
#include <GL/glew.h>
#include <GL/glut.h>
void init(void)
{
glClearColor(1.0, 1.0, 1.0, 0.0);
glMatrixMode(GL_PROJECTION);
gluOrtho2D(0.0, 200.0, 0.0, 160.0);
}
void lineSegment(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0, 0.0, 0.0);
glBegin(GL_LINES);
glVertex2i (180, 15);
glVertex2i (10, 145);
glEnd();
glFlush();
}
int main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowPosition(50, 100);
glutInitWindowSize(400, 300);
glutCreateWindow("Example OpenGL Program");
// Set this to true so GLEW knows to use a modern approach to retrieving function pointers and extensions
glewExperimental = GL_TRUE;
// Initialize GLEW to setup the OpenGL Function pointers
if(glewInit() != GLEW_OK) {
std::cout << "Failed to initialize GLEW" << std::endl;
return -1;
}
else {
std::cout << "GLEW is ok!" << std::endl;
}
init();
glutDisplayFunc(lineSegment);
glutMainLoop();
return 0;
}
3.2 测试glew+glfw
- CMakeLists.txt:
cmake_minimum_required(VERSION 3.16)
project(untitled1 LANGUAGES CXX)
set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
#####################
# glfw
find_package(glfw3 REQUIRED)
#####################
# glew
add_library(glew_static STATIC IMPORTED)
set_target_properties(glew_static PROPERTIES
IMPORTED_LOCATION /usr/lib64/libGLEW.a)
#####################
# opengl
find_package(OpenGL REQUIRED)
add_executable(untitled1
main.cpp
)
target_link_libraries(untitled1 glew_static OpenGL::GL glfw)
include(GNUInstallDirs)
install(TARGETS untitled1
LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
)
- main.cpp
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>
void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow *window);
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 300;
// 顶点着色器,GLSL语言
const char *vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main()\n"
"{\n"
" gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"}\0";
// 片元着色器
const char *fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
" FragColor = vec4(0.0f, 1.0f, 0.0f, 1.0f);\n"
"}\n\0";
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, "Ubuntu Opengl, yxy", 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;
// }
if(glewInit() != GLEW_OK) {
std::cout << "Failed to initialize GLEW" << std::endl;
return -1;
}
// build and compile our shader program
// ------------------------------------
// vertex shader
int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);
// check for shader compile errors
int success;
char infoLog[512];
glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
}
// fragment shader
int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);
// check for shader compile errors
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
}
// link shaders
int shaderProgram = glCreateProgram(); // shaderProgram 是多个着色器合并之后并最终链接完成的版本
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
// check for linking errors
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
}
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
float vertices[] = {
-0.5f, -0.5f, 0.0f, // left
0.5f, -0.5f, 0.0f, // right
0.0f, 0.5f, 0.0f // top
};
unsigned int VBO, VAO;
//创建VAO对象
glGenVertexArrays(1, &VAO);
glBindVertexArray(VAO);
//创建VBO对象,把顶点数组复制到一个顶点缓冲中,供OpenGL使用
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO); // 缓冲绑定到GL_ARRAY_BUFFER
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW); // 顶点数据复制到缓冲的内存中
//解释顶点数据方式
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0); // 顶点数据的解释
glEnableVertexAttribArray(0);
// 解绑VAO
glBindVertexArray(0);
// 解绑VBO
glBindBuffer(GL_ARRAY_BUFFER, 0);
// render loop
while (!glfwWindowShouldClose(window))
{
// input
processInput(window);
// render
glClearColor(1.0f, 0.7f, 0.7f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
// draw our first triangle
glUseProgram(shaderProgram);
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, 3);
glfwSwapBuffers(window);
glfwPollEvents();
}
// optional: de-allocate all resources
glDeleteVertexArrays(1, &VAO);
glDeleteBuffers(1, &VBO);
glDeleteProgram(shaderProgram);
glfwTerminate();
return 0;
}
//键盘按键回调函数
void processInput(GLFWwindow *window)
{
if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
}
//调整窗口大小回调函数
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
glViewport(0, 0, width, height);
}
结语
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