Opengl 3.3不会画任何东西.使用GLSL 330核心

问题描述

我正在遵循此站点的指南，并已停止在第2课上学习.起初，我尝试编写自己的代码，但在该代码不起作用后，我只是从站点中获取了代码.而且除了glClearColor之外，它什么也没画.

I am following the guides from this site and have stopped on the lesson 2. At first I have tried wiriting my own code but after it didn't work I have simply taken the code from the site. And it still doesn't draw anything besides the glClearColor.

我做了什么:

1. 检查了编译和链接.效果很好
2. 已检查的错误.不知道我是否做对了，但似乎一切都很好(我收到1280错误，但我已经读过GLEW会导致它，可以忽略它).
3. 在主循环中移动了glUseProgram，但没有得到任何结果.
4. 更改了颜色并尝试修改了着色器.还是没事

1. Checked compiling and linking. Works fine
2. Checked errors. Not sure if I have done it right but seems like everything's allright (I get a 1280 error but I have read that GLEW can cause it and it can be ignored).
3. Moved the glUseProgram through the main loop but didn't get any results.
4. Changed colors and tried modifying shaders. Still nothing

我将发布当前的代码(该网站的原始代码):

I will post the code I have at the moment (the original code from the site):

#include <stdio.h>
#include <stdlib.h>
#include <glew.h>
#include <glfw3.h>
#include <glm/glm.hpp>
#include <fstream>
#include <iostream>
#include <string>
#include <vector>


int max(int i, int j)
{
    if (i > j) return i;
    return j;
}


GLuint LoadShaders(const char * vertex_file_path, const char * fragment_file_path){

    // Create the shaders
    GLuint VertexShaderID = glCreateShader(GL_VERTEX_SHADER);
    GLuint FragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);

    // Read the Vertex Shader code from the file
    std::string VertexShaderCode;
    std::ifstream VertexShaderStream(vertex_file_path, std::ios::in);
    if (VertexShaderStream.is_open())
    {
        std::string Line = "";
        while (getline(VertexShaderStream, Line))
            VertexShaderCode += "\n" + Line;
        VertexShaderStream.close();
    }

    // Read the Fragment Shader code from the file
    std::string FragmentShaderCode;
    std::ifstream FragmentShaderStream(fragment_file_path, std::ios::in);
    if (FragmentShaderStream.is_open()){
        std::string Line = "";
        while (getline(FragmentShaderStream, Line))
            FragmentShaderCode += "\n" + Line;
        FragmentShaderStream.close();
    }

    GLint Result = GL_FALSE;
    int InfoLogLength;

    // Compile Vertex Shader
    printf("Compiling shader : %s\n", vertex_file_path);
    char const * VertexSourcePointer = VertexShaderCode.c_str();
    glShaderSource(VertexShaderID, 1, &VertexSourcePointer, NULL);
    glCompileShader(VertexShaderID);

    // Check Vertex Shader
    glGetShaderiv(VertexShaderID, GL_COMPILE_STATUS, &Result);
    glGetShaderiv(VertexShaderID, GL_INFO_LOG_LENGTH, &InfoLogLength);
    std::vector<char> VertexShaderErrorMessage(InfoLogLength);
    glGetShaderInfoLog(VertexShaderID, InfoLogLength, NULL, &VertexShaderErrorMessage[0]);
    fprintf(stdout, "%s\n", &VertexShaderErrorMessage[0]);

    // Compile Fragment Shader
    printf("Compiling shader : %s\n", fragment_file_path);
    char const * FragmentSourcePointer = FragmentShaderCode.c_str();
    glShaderSource(FragmentShaderID, 1, &FragmentSourcePointer, NULL);
    glCompileShader(FragmentShaderID);

    // Check Fragment Shader
    glGetShaderiv(FragmentShaderID, GL_COMPILE_STATUS, &Result);
    glGetShaderiv(FragmentShaderID, GL_INFO_LOG_LENGTH, &InfoLogLength);
    std::vector<char> FragmentShaderErrorMessage(InfoLogLength);
    glGetShaderInfoLog(FragmentShaderID, InfoLogLength, NULL, &FragmentShaderErrorMessage[0]);
    fprintf(stdout, "%s\n", &FragmentShaderErrorMessage[0]);

    // Link the program
    fprintf(stdout, "Linking program\n\n");
    GLuint ProgramID = glCreateProgram();
    glAttachShader(ProgramID, VertexShaderID);
    glAttachShader(ProgramID, FragmentShaderID);
    glLinkProgram(ProgramID);


    // Check the program
    glGetProgramiv(ProgramID, GL_LINK_STATUS, &Result);
    glGetProgramiv(ProgramID, GL_INFO_LOG_LENGTH, &InfoLogLength);
    std::vector<char> ProgramErrorMessage(max(InfoLogLength, int(1)));
    std::cout << "Checking program\n";

    glGetProgramInfoLog(ProgramID, InfoLogLength, NULL, &ProgramErrorMessage[0]);
    fprintf(stdout, "%s\n", &ProgramErrorMessage[0]);
    glDeleteShader(VertexShaderID);
    glDeleteShader(FragmentShaderID);
    std::cout << "END";

    return ProgramID;
}


int main(void)
{
    if (!glfwInit())
    {
        std::cout << "Cannot init glfw";
        return -1;
    }

    //glfwWindowHint(GLFW_SAMPLES, 4); // 4x antialiasing
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); // We want OpenGL 3.3
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // To make MacOS happy; should not be needed
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); //We don't want the old OpenGL



    // Open a window and create its OpenGL context
    GLFWwindow* window; // (In the accompanying source code, this variable is global)
    window = glfwCreateWindow(1024, 768, "Tutorial 01", NULL, NULL);
    if (window == NULL){
        fprintf(stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.\n");
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window); // Initialize GLEW
    glewExperimental = GL_TRUE; // Needed in core profile
    if (glewInit() != GLEW_OK) {
        fprintf(stderr, "Failed to initialize GLEW\n");
        return -1;
    }

    // Ensure we can capture the escape key being pressed below
    glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);


    // This will identify our vertex buffer
    GLuint vertexbuffer;

    // Generate 1 buffer, put the resulting identifier in vertexbuffer
    glGenBuffers(1, &vertexbuffer);

    // The following commands will talk about our 'vertexbuffer' buffer
    glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);

    // Give our vertices to OpenGL.
    static const GLfloat g_vertex_buffer_data[] = {
        -1.0f, -1.0f, 0.0f,
        1.0f, -1.0f, 0.0f,
        0.0f, 1.0f, 0.0f
    };
    glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);

    glClearColor(0.0f, 0.0f, 0.4f, 0.0f);
    GLuint programID = LoadShaders("res\\vertex.glsl", "res\\fragment.glsl");

    do{

        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glUseProgram(programID);

        glEnableVertexAttribArray(0);
        glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
        glVertexAttribPointer(
            0,                  // attribute 0. No particular reason for 0, but must match the layout in the shader.
            3,                  // size
            GL_FLOAT,           // type
            GL_FALSE,           // normalized?
            0,                  // stride
            (void*)0            // array buffer offset
            );

        // Draw the triangle !
        glDrawArrays(GL_TRIANGLES, 0, 3); // Starting from vertex 0; 3 vertices total -> 1 triangle

        glDisableVertexAttribArray(0);

        // Swap buffers
        glfwSwapBuffers(window);
        glfwPollEvents();


    } // Check if the ESC key was pressed or the window was closed
    while (glfwGetKey(window, GLFW_KEY_ESCAPE) != GLFW_PRESS &&
    glfwWindowShouldClose(window) == 0);

    return 0;
}

fragment.glsl

#version 330 core
out vec3 color;

void main(){
    color = vec3(1,1,0);
}

vertex.glsl

#version 330 core

layout(location = 0) in vec3 vertexPosition_modelspace;
void main(){
gl_Position.xyz = vertexPosition_modelspace;
    gl_Position.w = 1.0;
 }

推荐答案

OpenGL核心配置文件要求使用顶点数组对象(VAO).这是在规范的不建议使用和已删除的功能"中:

The OpenGL Core Profile requires the use of Vertex Array Objects (VAOs). This is in the "Deprecated and Removed Features" of the spec:

您正在使用的教程建议将此代码用作初始化的一部分:

The tutorial you are using suggests to use this code as part of your initialization:

GLuint VertexArrayID;
glGenVertexArrays(1, &VertexArrayID);
glBindVertexArray(VertexArrayID);

这足以使教程代码正常工作.为了在更复杂的应用程序中有效使用VAO，您可能需要为每个对象创建一个VAO.然后，它将跟踪对象的完整顶点设置状态，并允许您在绘制之前通过一次glBindVertexArray()调用来设置状态.

This will be enough to get the tutorial code working. To make productive use of VAOs in more complex applications, you will probably want to create a VAO for each object. This will then track the full vertex setup state for the object, and allow you to set the state with a single glBindVertexArray() call before drawing.

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