使用OpenGL绘制一个矩形和一个三角形
使用OpenGL绘制一个矩形和一个三角形
软件：VS
语言：C++
库
引入两个库一个是glew和glfw
具体步骤可看此知乎步骤
https://zhuanlan.zhihu.com/p/559251417
部分参考
[]((4条消息) OpenGL——绘制三角形和矩形_Simple J的博客-CSDN博客_opengl绘制矩形代码)
资源文件
这部分内容命名可以随意，但是后缀名一定不能修改！
core.vs
在资源文件中新建一个core.vs文档
#version 330 core
layout(location = 0) in vec3 position;
void main()
{
gl_Position = vec4(position,1.0f);
}
更改gl位置
core.fs
在资源文件中新建一个core.fs文档
#version 330 core
out vec4 FragColor;
void main()
{
FragColor = vec4(1.0f,0.0f,0.0f,1.0f);
}
可以修改图形的颜色
头文件
在头文件中新建命名为Shader.h文件
#pragma once
#include
#include
#include
#include
#include
class Shader {
public:
//GLuint ShaderProgram;
Shader(const char* vertexPath, const char* fragmentPath)
{
ShaderProgram = glCreateProgram();
CompileShaderFromFile(vertexPath, GL_VERTEX_SHADER);
CompileShaderFromFile(fragmentPath, GL_FRAGMENT_SHADER);
glLinkProgram(ShaderProgram);
CheckErrors(ShaderProgram, "PROGRAM", GL_LINK_STATUS);
#ifndef __APPLE__
glValidateProgram(ShaderProgram);
CheckErrors(ShaderProgram, "PROGRAM", GL_VALIDATE_STATUS);
#endif //!__APPLE__
}
~Shader()
{
glDeleteProgram(ShaderProgram);
}
void UseProgram()
{
glUseProgram(ShaderProgram);
}
private:
GLuint ShaderProgram;
void CompileShaderFromFile(const char* path, GLenum shaderType)
{
std::string code;
std::ifstream shaderFile;
shaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
try {
shaderFile.open(path);
std::stringstream shaderStream;
shaderStream << shaderFile.rdbuf();
shaderFile.close();
code = shaderStream.str();
}
catch (std::ifstream::failure& e)
{
std::cout << "ERROR::SHADER::FILE_NOT_SUCCESSFULLU_READ:" << e.what() << std::endl;
}
const GLchar* shaderCode = code.c_str();
GLuint shader = glCreateShader(shaderType);
glShaderSource(shader, 1, &shaderCode, NULL);
glCompileShader(shader);
CheckErrors(shader, "SHADER", GL_COMPILE_STATUS);
glAttachShader(ShaderProgram, shader);
glDeleteShader(shader);
}
void CheckErrors(GLuint obj, std::string type, GLenum checkStatus)
{
GLint success;
if (type == "SHADER")
{
glGetShaderiv(obj, checkStatus, &success);
if (!success)
{
GLchar infoLog[1024];
glGetShaderInfoLog(obj, 1024, NULL, infoLog);
std::cout << "ERROR::SHADER::COMPILATION_FAILED\n" << infoLog << std::endl;
exit(-1);
}
}
else if (type == "PROGRAM")
{
glGetProgramiv(obj, checkStatus, &success);
if (!success)
{
GLchar infoLog[1024];
glGetProgramInfoLog(obj, 1024, NULL, infoLog);
std::cout << "ERROR::PROGRAM::COMPILATION_FAILED\n" << infoLog << std::endl;
exit(-1);
}
}
}
};
源文件
在源文件中新建命名为main.cpp文件
#include
#include
#include
#include "Shader.h"
#define ERRORLOG(message) std::cout << message << std::endl;glfwTerminate();return -1;
/*
const GLchar* vertexShaderSource = "$version 330 core\n"
"layout(location = 0) in vec3 position;\n"
"void main()\n"
"{\n"
"gl_Position = vec4(position,1.0f);\n"
"}";
const GLchar* fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
"FragColor = vec4(1.0f,0.0f,0.0f,0.0f);\n"
"}";
static void CreateShaderProgram(GLuint shaderProgram)
{
GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);
GLint success;
GLchar infoLog[1024];
glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(vertexShader, 1024, NULL, infoLog);
std::cout << "ERROR::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
}
GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(fragmentShader, 1024, NULL, infoLog);
std::cout << "ERROR::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
}
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success)
{
glGetProgramInfoLog(shaderProgram, 1024, NULL, infoLog);
std::cout << "ERROR::PROGRAM::LINK_FAILED\n" << infoLog << std::endl;
}
#ifndef __APPLE__
glValidateProgram(shaderProgram);
glGetProgramiv(shaderProgram, GL_VALIDATE_STATUS, &success);
if (!success)
{
glGetProgramInfoLog(shaderProgram, 1024, NULL, infoLog);
std::cout << "ERROR::PROGRAM::VALIDATION_FAILED\n" << infoLog << std::endl;
}
#endif
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
}
*/
GLuint VAO, VBO,VEO;
static void RenderScreen(GLFWwindow* window)
{
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);//界面颜色
glClear(GL_COLOR_BUFFER_BIT);
glBindVertexArray(VAO);
//glDrawArrays(GL_POINTS, 0, 1);
glDrawArrays(GL_TRIANGLES, 4, 3);//三角形
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);//矩形
glBindVertexArray(0);
glfwSwapBuffers(window);
}
static void CreateVertexBuffer()
{
GLfloat vertices1[] = {
-1.0f, 0.0f, 0.0f, // 左
0.0f, 0.0f, 0.0f, // 右
-0.5f, 0.5f, 0.0f // 顶点
};
GLfloat vertices2[] = {
0.5f, 0.0f, 0.0f, // 右上角
0.5f, -0.5f, 0.0f, // 右下角
0.0f, -0.5f, 0.0f,// 左下角
1.0f, 0.0f, 0.0f,// 左上角
};
unsigned int indices[] = { // 注意索引从0开始!
0, 1, 3, // 第一个三角形
1, 2, 3 // 第二个三角形
};
GLfloat vertices[] = {
//矩形
0.5f, 0.0f, 0.0f, // 右上角
0.5f, -0.5f, 0.0f, // 右下角
0.0f, -0.5f, 0.0f,// 左下角
0.0f, 0.0f, 0.0f,// 左上角
//三角形
-1.0f, 0.0f, 0.0f, // 左
0.0f, 0.0f, 0.0f, // 右
-0.5f, 0.5f, 0.0f // 顶点
};
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);//三角形
glGenBuffers(1, &VEO);//矩形
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);//三角形
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, VEO);//矩形
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
}
static void SetViewport(GLFWwindow* window)
{
int screenWidth, screenHeight;
glfwGetFramebufferSize(window, &screenWidth, &screenHeight);
glViewport(0, 0, screenWidth, screenHeight);
}
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);
#ifdef __APPLE__
glfwWindowHint(GLFE_OPENGL_FORENGL_FOREARD_COMPAT, GL_TRUE);
#endif //__APPLE__
GLFWwindow* window = glfwCreateWindow(800, 600, "OpenGLTutorial1", NULL, NULL);
if (window == NULL) { ERRORLOG("Failde to creat GLFW window") }
glfwMakeContextCurrent(window);
if (GLEW_OK != glewInit()) { ERRORLOG("Failed tp init glew") }
CreateVertexBuffer();
Shader shader = Shader("res/core.vs", "res/core.fs");
//GLuint ShaderProgram = glCreateProgram();
//CreateShaderProgram(ShaderProgram);
while (!glfwWindowShouldClose(window))
{
SetViewport(window);
glfwPollEvents();
//glUseProgram(ShaderProgram);
shader.UseProgram();
RenderScreen(window);
}
glfwTerminate();
return 1;
}
运行结果
可能问题
- 打代码的过程中可能会飘红，就是引入库失败，思考可能是引入glew和glfw路径不对
明明一开始和教程一步步配置的怎么可能会出错！后来和舍友对比后，发现在新建项目的时候，有一个地方不能勾选
就是这儿！因为如果勾选了的话路径就和教程中的不一样了。可以看看下图如果勾选了的文件里是啥
下图是没勾选的，新建完后可以去你的项目文件夹下面看看。如果和下图一致那就没问题
- 还有一种情况就是代码没飘红，能运行，但是运行出来是这样，如下图
error原因是打不开文件，思考应该是fs和vs两个文件路径不对。看了看代码
果然，因为是上课跟着老师打的，根本没有res这个文件夹哈哈哈哈。那就要去Project5文件下自己新建一个res文件夹，然后把core.fs和core.vs两个文件放进去，如下图
注意看清楚res的路径哦
改进
就是如何让两个图形的颜色不一样，再能改下他们的位置吧，可能在下篇笔记放出来（如果有时间的话哈哈哈）