HelloTriangle.cpp

#include "HelloTriangle.h"
#include<iostream>
#include<glad/glad.h>
#include<GLFW/glfw3.h>
void processInput(GLFWwindow *window)
{
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);
}
void HelloTriangle::HelloTriangle(GLFWwindow* window){
    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";
    const char *fragmentShaderSource = "#version 330 core\n"
    "out vec4 FragColor;\n"
    "void main()\n"
    "{\n"
    "FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
    "}\0";
    
    unsigned int vertexShader;
    vertexShader = glCreateShader(GL_VERTEX_SHADER); // 创建一个顶点着色器
    glShaderSource(vertexShader,1,&vertexShaderSource,NULL);//参数依次为着色器对象，着色器代码字符串数量，源码
    glCompileShader(vertexShader);

    unsigned int fragmentShader;
    fragmentShader = glCreateShader(GL_FRAGMENT_SHADER); 
    glShaderSource(fragmentShader,1,&fragmentShaderSource,NULL);
    glCompileShader(fragmentShader);

    unsigned int shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram,vertexShader);
    glAttachShader(shaderProgram,fragmentShader);
    glLinkProgram(shaderProgram);
    glDeleteShader(fragmentShader);
    glDeleteShader(vertexShader);
    
    float vertices[] = {
        -0.5f, -0.5f, 0.0f,
        0.5f, -0.5f, 0.0f,
        0.0f,  0.5f, 0.0f
    };
    unsigned int VBO;
    glGenBuffers(1,&VBO);
    
    unsigned int VAO;
    glGenVertexArrays(1,&VAO);
    glBindVertexArray(VAO);

glBindBuffer(GL_ARRAY_BUFFER,VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,sizeof(float)*3,(void*)0);
    glEnableVertexAttribArray(0);
    
    glBindBuffer(GL_ARRAY_BUFFER, 0); 
    glBindVertexArray(0); 

     

    //检测是否有错误
    int success;
    char infoLog[512];
    glGetShaderiv(vertexShader,GL_COMPILE_STATUS,&success);
    if(!success){
        glGetShaderInfoLog(vertexShader,512,NULL,infoLog);
        std::cout<<"error log:"<<infoLog<<std::endl;
    }


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

        // render
        // ------
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        // draw our first triangle
        glUseProgram(shaderProgram);
        glBindVertexArray(VAO); // seeing as we only have a single VAO there's no need to bind it every time, but we'll do so to keep things a bit more organized
        glDrawArrays(GL_TRIANGLES, 0, 3);
        // glBindVertexArray(0); // no need to unbind it every time 
 
        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        // -------------------------------------------------------------------------------
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    // optional: de-allocate all resources once they've outlived their purpose:
    // ------------------------------------------------------------------------
    glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);
    glDeleteProgram(shaderProgram);

    // glfw: terminate, clearing all previously allocated GLFW resources.
    // ------------------------------------------------------------------
    glfwTerminate();
    return ;
}
void HelloTriangle::DrawTwoTriangles(GLFWwindow* window){
    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";
    const char *fragmentShaderSource = "#version 330 core\n"
    "out vec4 FragColor;\n"
    "void main()\n"
    "{\n"
    "FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
    "}\0";
    float vertices[] = {
        0.5f, 0.5f, 0.0f,   // 右上角
        0.5f, -0.5f, 0.0f,  // 右下角
        -0.5f, -0.5f, 0.0f, // 左下角
        -0.5f, 0.5f, 0.0f   // 左上角
    };
    unsigned int index[] = {
        0,1,3,
        1,2,3
    };
    auto vertex_shader_program = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertex_shader_program,1,&vertexShaderSource,NULL);
    glCompileShader(vertex_shader_program);

    auto fragment_shared_program = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragment_shared_program,1,&fragmentShaderSource,NULL);
    glCompileShader(fragment_shared_program);
    
    auto program1 = glCreateProgram();
    glAttachShader(program1,vertex_shader_program);
    glAttachShader(program1,fragment_shared_program);
    glLinkProgram(program1);
    glDeleteShader(fragment_shared_program);
    glDeleteShader(vertex_shader_program);

    GLuint VBO,VAO,EBO;
    glGenVertexArrays(1, &VAO); 
    glBindVertexArray(VAO);
    

    glGenBuffers(1,&VBO);
    glBindBuffer(GL_ARRAY_BUFFER,VBO);
    glBufferData(GL_ARRAY_BUFFER,sizeof(vertices),vertices,GL_STATIC_DRAW);
    
    glGenBuffers(1,&EBO);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,EBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER,sizeof(index),index,GL_STATIC_DRAW);

    glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,3*sizeof(float),(void*)0);
    glEnableVertexAttribArray(0); // 开启VertexAttri
    glBindVertexArray(0);

    glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);

    while(!glfwWindowShouldClose(window)){
        glUseProgram(program1);
        glBindVertexArray(VAO);

        //glDrawArrays(GL_TRIANGLES,0,3);
        glDrawElements(GL_TRIANGLES,6,GL_UNSIGNED_INT,NULL);
        glfwSwapBuffers(window);
        glBindVertexArray(0);
        glfwPollEvents();

    }
    glDeleteProgram(program1);
    glfwTerminate();
    
}