c++ - 生成缓冲区时出现 OpenGL 段错误

Question

我正在使用统一 block ，但在为它们创建统一缓冲区时遇到了问题。问题是当在某个地方生成缓冲区时(如第一个代码示例所示，大约向下 2/3)，在 glClear(); 期间发生段错误；

有趣的是，glGenBuffers 的顺序很重要，因为如果我交换对函数的 2 次调用，就不会发生段错误。

程序.cpp:

#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <helpful.hpp> //Contains text read and shader loading functions


using namespace std;


int main(int args, char* argv[])
{
    //## Create context ##//
    unsigned int a;
    glfwInit();


    glfwWindowHint(GLFW_DEPTH_BITS,16);

    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 1);

    GLFWwindow* window = glfwCreateWindow(1368, 768, "", NULL, NULL);

    glfwMakeContextCurrent(window);


    glewExperimental=GL_TRUE;
    glewInit();

    cout << "GL context created" << endl;

    a = glGetError();
    if (a!=0)cout << "Context error" << a << endl;

    glViewport(0, 0, 1368, 768);


    //## Setup shader ##//

    const char* vsText = textFileRead("shaders/testShader/shader.vert");    //Reads a text file
    const char* fsText = textFileRead("shaders/testShader/shader.frag");

    string vsource = "#version 140 \n";
    string fsource = "#version 140 \n";

    vsource += vsText;
    fsource += fsText;

    array<GLuint, 3> out = loadShaders("testShader",vsource,fsource);

    GLuint shader_id = out[0];
    GLuint shader_vp = out[1];
    GLuint shader_fp = out[2];

    glBindAttribLocation(shader_id, 0, "in_Vertex");
    glBindFragDataLocation(shader_id, 0, "out_Scene");

    glAttachShader(shader_id, shader_fp);
    glAttachShader(shader_id, shader_vp);
    glLinkProgram(shader_id);

    glUseProgram(shader_id);

    cout << "s : " << shader_id << endl;

    GLuint globalIndex = glGetUniformBlockIndex(shader_id, "GlobalSettings");
    glUniformBlockBinding(shader_id, globalIndex, 1);

    GLuint modelIndex = glGetUniformBlockIndex(shader_id, "ModelSettings");
    glUniformBlockBinding(shader_id, modelIndex, 2);


    //## Fill Uniform block buffers ##//

    float f[16] = {
        1.f,    .2f,    1.f,    .2f,
        1.f,    .2f,    1.f,    .2f,
        1.f,    .2f,    1.f,    .2f,
        1.f,    .2f,    1.f,    .6f,
    };

    GLuint subo; //"GlobalSettings" block
    glGenBuffers(1, &subo);
    glBindBuffer(GL_UNIFORM_BUFFER, subo);
    glBufferData(GL_UNIFORM_BUFFER, sizeof(float) * 16, f, GL_DYNAMIC_DRAW);
    glBindBufferBase(GL_UNIFORM_BUFFER, subo, 1);

    //This is what causes the error
    //Comment out these 2 lines and it works
    //Or swap this block with the one below
    GLuint b;
    glGenBuffers(1, &b);

    GLuint mubo; //"ModelSettings" block
    glGenBuffers(1, &mubo);
    glBindBuffer(GL_UNIFORM_BUFFER, mubo);
    glBufferData(GL_UNIFORM_BUFFER, sizeof(float) * 16, f, GL_DYNAMIC_DRAW);
    glBindBufferBase(GL_UNIFORM_BUFFER, mubo, 2);





    //## Create a simple quad to draw on screen ##//
    GLuint vao;
    GLuint vbo;
    glGenVertexArrays(1, &vao);
    glGenBuffers(1, &vbo);

    std::vector<glm::vec3> v;

    v.push_back(glm::vec3(-1.,-1.,0));
    v.push_back(glm::vec3(1.,-1.,0));
    v.push_back(glm::vec3(1.,1.,0));
    v.push_back(glm::vec3(-1.,-1.,0));
    v.push_back(glm::vec3(1.,1.,0));
    v.push_back(glm::vec3(-1.,1.,0));

    glBindVertexArray(vao);

    glEnableVertexAttribArray(0);

    int numVertices = v.size();
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, numVertices * sizeof(GLfloat) * 3, v.data(), GL_STATIC_DRAW);
    glVertexAttribPointer((GLuint)0, 3, GL_FLOAT, GL_FALSE, 0, 0);

    glBindVertexArray(0);

    glfwPollEvents();

    glClearColor(0.2,0.2,0.2,1);
    while (true)
    {
        glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

        glBindVertexArray(vao);
        glUseProgram(shader_id);
        glDrawArrays(GL_TRIANGLES, 0, numVertices);
        glBindVertexArray(0);

        glfwSwapBuffers(window);
    }

}

这是着色器:

顶点:

layout( std140 ) uniform GlobalSettings {
    mat4 projectionMatrix;
};

layout( std140 ) uniform ModelSettings {
    mat4 MVMatrix;
};

in vec3 in_Vertex;
in vec3 in_Normal;

out vec4 eyePosition;
out vec4 screenPosition;

out vec3 pass_Normal;

void main(void)
{
    vec4 vertex=vec4(in_Vertex, 1.0);

    eyePosition = MVMatrix * vertex;

    screenPosition = gl_Position = vertex;

    pass_Normal = in_Normal;

}

片段

layout( std140 ) uniform GlobalSettings {
    mat4 projectionMatrix;
};

layout( std140 ) uniform ModelSettings {
    mat4 MVMatrix;
};


in vec4 screenPosition;
in vec4 eyePosition;
in vec3 pass_Normal;
out vec4 out_Scene;

void main(void)
{   
    float d = dot(normalize(pass_Normal), vec3(0,0,-1));
    float a = 1;
    //if(d>0)a=1;
    out_Scene = vec4(MVMatrix[3][1],MVMatrix[3][2],MVMatrix[3][3],a);
}

着色器加载函数可以在这里找到http://pastebin.com/XqewS28W需要的。

Answer 1

问题是 glBindBufferBase 中的参数是错误的方式，因此索引参数被赋予了缓冲区名称，反之亦然。它只是巧合地工作，因为缓冲区名称恰好与索引相同，并且在额外缓冲区中生成导致索引不再与缓冲区匹配。