大量修改

Question

我对glDrawElements的调用产生了分段错误。如果我废弃索引并使用glDrawArrays绘制了顶点缓冲区中的所有内容。所以我的假设是错误与我填充GL_ELEMENT_ARRAY_BUFFER的方式有关，但我没有看到问题。

我有一个球体类，可以为球体生成顶点和索引。然后我只需要以下代码来设置vbo，vao等：

    GLuint vbo;
    glGenBuffers(1, &vbo);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(struct VertexData) * sphere.GetVertices()->size(), sphere.GetVertices()->data(), GL_STATIC_DRAW);
    glBindBuffer(GL_ARRAY_BUFFER, 0);

    GLuint vao;
    glGenVertexArrays(1,&vao);
    glBindVertexArray(vao);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 4, GL_DOUBLE, GL_FALSE, sizeof(struct VertexData), (const GLvoid*)offsetof(struct VertexData, position));
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(struct VertexData), (const GLvoid*)offsetof(struct VertexData, color));
    glEnableVertexAttribArray(2);
    glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(struct VertexData), (const GLvoid*)offsetof(struct VertexData, normal));
    glEnableVertexAttribArray(3);
    glVertexAttribPointer(3, 2, GL_FLOAT, GL_FALSE, sizeof(struct VertexData), (const GLvoid*)offsetof(struct VertexData, tcoords));

    GLuint ibo;
    glGenBuffers(1, &ibo);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLushort) * sphere.GetIndices()->size(), sphere.GetIndices()->data(), GL_STATIC_DRAW);
    glBindVertexArray(0);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

..我在其中看不到任何错误。

我的绘图就是这样完成的：

glClearColor(0.0, 0.0, 0.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

float t = watch.GetElapsedTimePeriod().count();
float rotation = 0.5/1000.0*t;
rotationMatrix = glm::rotate(rotationMatrix,rotation,glm::vec3(0,1,0));
glm::mat4 modelMatrix = perspectiveMatrix * viewMatrix * rotationMatrix * identitymatrix;

glUseProgram(shaderprogram);
glUniformMatrix4fv(glGetUniformLocation(shaderprogram, "mvpmatrix"), 1, GL_FALSE, glm::value_ptr(modelMatrix));

glBindVertexArray(vao);
std::shared_ptr<std::vector<GLushort>> p = sphere.GetIndices();
size_t tt = p->size();
glDrawElements(GL_TRIANGLES,tt,GL_UNSIGNED_SHORT,0);
//glDrawArrays(GL_POINTS,0,(*sphere.GetVertices()).size());
glBindVertexArray(0);

glUseProgram(0);

SDL_GL_SwapWindow(sdlglHandler);

如果我使用它，您可以看到我注释掉的glDrawArrays调用成功（并且不要在顶部代码中设置索引缓冲区）。（它是GL_POINTS所以我可以看到每个被绘制的顶点。）

我已经注意到，如果我在我的球体中产生较少的顶点，程序就不会崩溃。所以起初我认为使用GLushort作为我的索引的类型，但是没有为它生成许多顶点是一个问题。我也使用了GLuint进行了测试，但没有做任何事情。

接下来，我注意到如果我使用的索引数量小于我的指数矢量（从球体返回），我可以让它工作;但它必须是大小的1/6（当然只有我球体三角形的1/6左右。

我已经查看了我的其余代码，看看我是否正在编写一个数组或其他内容，而且只是在我使用的openGL代码中。用数组和指针做任何事情。

因为我能够删除索引数组并看到它正常工作，所以我确信它与此有关;但是我无法解决这个问题。

哦，最后，VertexData结构如下所示：

struct VertexData
{
    GLdouble position[4];
    GLfloat color[3];
    GLfloat normal[3];
    GLfloat tcoords[2];
};

大量修改

我已经删除了所有的C ++封装并生成了这个代码，这给了我同样的错误。我完全失去了看到试图访问私人记忆的地方，看起来没有什么东西溢满了我：

#include <exception>
#include <iostream>
#include <fstream>
#include <sstream>
#include <list>
#include <string>
#include <algorithm>
#include <functional>

#include <utilities.hpp>

#include <GL/glew.h>
#include <SDL2/sdl.h>
#define GLM_FORCE_RADIANS
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <glm/gtx/transform.hpp>

struct VertexData
{
    GLdouble position[4];
    GLfloat color[3];
    GLfloat normal[3];
    GLfloat tcoords[2];
};

int main(int argc, char* argv[])
{
    try
    {
        SDL_Window* window;
        SDL_GLContext context;
        if(SDL_Init(SDL_INIT_VIDEO) < 0)
            throw std::runtime_error("unable to initialise video");

        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 4);

        SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
        SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
        SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1);
        SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES, 4);

        window = SDL_CreateWindow("SpaceEngine", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
        800, 800, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);
        if(!window)
            throw std::runtime_error("unable to create window");

        context = SDL_GL_CreateContext(window);

        SDL_GL_SetSwapInterval(1);

        GLenum glewErr = glewInit();
        if(glewErr != GLEW_OK)
        {
            SDL_GL_DeleteContext(context);
            SDL_DestroyWindow(window);
            SDL_Quit();
            throw std::runtime_error(reinterpret_cast<const char*>(glewGetErrorString(glewErr)));
        }

        glEnable(GL_DEPTH_TEST);
        glDepthFunc(GL_LESS);

        std::vector<VertexData> vertices;
        std::vector<GLushort> indices;
        int rings = 200;
        int sectors = 200;
        float radius = 1.0;

        if(rings < 2)
            rings = 2;
        if(sectors < 2)
            sectors = 2;
        while(rings * sectors >= std::numeric_limits<GLushort>::max())
        {
            rings /= 2;
            sectors /= 2;
        }

        const GLuint polyCountXPitch = rings+1;

        GLuint level = 0;

        for(GLuint p1 = 0; p1 < sectors-1; ++p1)
        {
            for(GLuint p2 = 0; p2 < rings-1; ++p2)
            {
                GLuint curr = level + p2;
                indices.push_back(curr + polyCountXPitch);
                indices.push_back(curr);
                indices.push_back(curr + 1);
                indices.push_back(curr + polyCountXPitch);
                indices.push_back(curr + 1);
                indices.push_back(curr + 1 + polyCountXPitch);
            }

            indices.push_back(level + rings - 1 + polyCountXPitch);
            indices.push_back(level + rings - 1);
            indices.push_back(level + rings);

            indices.push_back(level + rings - 1 + polyCountXPitch);
            indices.push_back(level + rings);
            indices.push_back(level + rings + polyCountXPitch);

            level += polyCountXPitch;
        }

        const GLuint polyCountSq = polyCountXPitch * sectors;           //top point
        const GLuint polyCountSq1 = polyCountSq + 1;                    //bottom point
        const GLuint polyCountSqM1 = (sectors - 1) * polyCountXPitch;   //last rows first index

        for(GLuint p2 = 0; p2 < rings - 1; ++p2)
        {
            indices.push_back(polyCountSq);
            indices.push_back(p2 + 1);
            indices.push_back(p2);

            indices.push_back(polyCountSqM1 + p2);
            indices.push_back(polyCountSqM1 + p2 + 1);
            indices.push_back(polyCountSq1);
        }

        indices.push_back(polyCountSq);
        indices.push_back(rings);
        indices.push_back(rings - 1);

        indices.push_back(polyCountSqM1 + rings - 1);
        indices.push_back(polyCountSqM1);
        indices.push_back(polyCountSq1);

        const GLdouble angleX = 2 * pi() / rings;
        const GLdouble angleY = pi() / sectors;

        GLuint i = 0;
        GLdouble axz;
        GLdouble ay = 0;

        vertices.resize(polyCountXPitch * sectors + 2);
        for(GLuint y = 0; y < sectors; ++y)
        {
            ay += angleY;
            const GLdouble sinay = std::sin(ay);
            axz = 0;

            for(GLuint xz = 0; xz < rings; ++xz)
            {
                const glm::vec3 pos((radius * std::cos(axz) * sinay),radius * std::cos(ay), radius * std::sin(axz) * sinay);
                glm::vec3 normal = pos;
                normal = glm::normalize(normal);

                GLuint tu = 0.5f;
                if(y == 0)
                {
                    if(normal.y != -1.0f && normal.y != 1.0f)
                        tu = std::acos(glm::clamp<GLdouble>(normal.x/sinay, -1.0f, 1.0f)) * 0.5 * (1.0f/pi());
                    if(normal.z < 0.0f)
                        tu = 1 - tu;
                }
                else
                    tu = vertices[i-polyCountXPitch].tcoords[0];

                VertexData v;
                v.color[0] = 1;
                v.color[1] = 1;
                v.color[2] = 1;
                v.position[0] = pos.x;
                v.position[1] = pos.y;
                v.position[2] = pos.z;
                v.position[3] = 1.0f;
                v.normal[0] = normal.x;
                v.normal[1] = normal.y;
                v.normal[2] = normal.z;
                v.tcoords[0] = tu;
                v.tcoords[1] = ay * (1.0f/pi());
                vertices.at(i) = v;

                ++i;
                axz += angleX;
            }

            vertices.at(i) = vertices.at(i - rings);
            vertices.at(i).tcoords[0] = 1.0f;
            ++i;
        }

        VertexData v;
        v.color[0] = 1;
        v.color[1] = 1;
        v.color[2] = 1;
        v.position[0] = 0;
        v.position[1] = radius;
        v.position[2] = 0;
        v.position[3] = 1.0f;
        v.normal[0] = 0;
        v.normal[1] = 1;
        v.normal[2] = 0;
        v.tcoords[0] = 0.5f;
        v.tcoords[1] = 0.0f;
        vertices.at(i) = v;
        ++i;
        v.position[1] = -radius;
        v.normal[1] = -1.0f;
        v.tcoords[1] = 1.0f;
        vertices.at(i) = v;

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

        GLuint vbo;
        glGenBuffers(1, &vbo);
        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        glBufferData(GL_ARRAY_BUFFER, sizeof(struct VertexData) * vertices.size(), vertices.data(), GL_STATIC_DRAW);

        glEnableVertexAttribArray(0);
        glVertexAttribPointer(0, 4, GL_DOUBLE, GL_FALSE, sizeof(struct VertexData), (const GLvoid*)offsetof(struct VertexData, position));
        glEnableVertexAttribArray(1);
        glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(struct VertexData), (const GLvoid*)offsetof(struct VertexData, color));
        glEnableVertexAttribArray(2);
        glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(struct VertexData), (const GLvoid*)offsetof(struct VertexData, normal));
        glEnableVertexAttribArray(3);
        glVertexAttribPointer(3, 2, GL_FLOAT, GL_FALSE, sizeof(struct VertexData), (const GLvoid*)offsetof(struct VertexData, tcoords));

        GLuint ibo;
        glGenBuffers(1, &ibo);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLushort) * indices.size(), indices.data(), GL_STATIC_DRAW);

        glBindVertexArray(0);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

        GLuint shader1,shader2;
        std::ifstream file("tutorial2.vert");
        if(!file)
            throw std::runtime_error("The file tutorial2.vert was not opened");
        else
        {
            std::string fileContents((std::istreambuf_iterator<char>(file)),std::istreambuf_iterator<char>());

            shader1 = glCreateShader(GL_VERTEX_SHADER);
            std::string fail = "glCreateShader failed using " + GL_VERTEX_SHADER;

            if(!shader1)
                throw std::runtime_error(fail.c_str());

            const GLchar* contents[1];
            contents[0] = fileContents.c_str();
            glShaderSource(shader1, 1, contents, NULL);

            glCompileShader(shader1);
            int compiled;
            glGetShaderiv(shader1, GL_COMPILE_STATUS, &compiled);
            if(compiled == 0)
            {
                int maxLength;
                glGetShaderiv(shader1, GL_INFO_LOG_LENGTH, &maxLength);
                char* vertexInfoLog = new char[maxLength];
                glGetShaderInfoLog(shader1, maxLength, &maxLength, vertexInfoLog);
                throw std::runtime_error("Shader failed to compile:\n>\t" + std::string(vertexInfoLog));
            }
        }
        std::ifstream file2("tutorial2.frag");
        if(!file2)
            throw std::runtime_error("The file tutorial2.frag was not opened");
        else
        {
            std::string fileContents((std::istreambuf_iterator<char>(file2)),std::istreambuf_iterator<char>());

            shader2 = glCreateShader(GL_FRAGMENT_SHADER);
            std::string fail = "glCreateShader failed using " + GL_FRAGMENT_SHADER;
            if(!shader2)
                throw std::runtime_error(fail.c_str());

            const GLchar* contents[1];
            contents[0] = fileContents.c_str();
            glShaderSource(shader2, 1, contents, NULL);

            glCompileShader(shader2);
            int compiled;
            glGetShaderiv(shader2, GL_COMPILE_STATUS, &compiled);
            if(compiled == 0)
            {
                int maxLength;
                glGetShaderiv(shader2, GL_INFO_LOG_LENGTH, &maxLength);
                char* vertexInfoLog = new char[maxLength];
                glGetShaderInfoLog(shader2, maxLength, &maxLength, vertexInfoLog);
                throw std::runtime_error("Shader failed to compile:\n>\t" + std::string(vertexInfoLog));
            }
        }

        GLuint program = glCreateProgram();
        if(!program)
            throw std::runtime_error("glCreateProgram failed");

        glAttachShader(program, shader1);
        glAttachShader(program, shader2);

        glBindAttribLocation(program, 0, "in_Position");
        glBindAttribLocation(program, 1, "in_Color");
        glBindAttribLocation(program, 2, "in_Normal");
        glBindAttribLocation(program, 3, "in_UV");

        glLinkProgram(program);
        int IsLinked;
        glGetProgramiv(program, GL_LINK_STATUS, (int *)&IsLinked);
        if(IsLinked == 0)
        {
           int maxLength;
           glGetProgramiv(program, GL_INFO_LOG_LENGTH, &maxLength);
           char* shaderProgramInfoLog = new char[maxLength];
           glGetProgramInfoLog(program, maxLength, &maxLength, shaderProgramInfoLog);
           throw std::runtime_error("Program failed to link:\n>\t" + std::string(shaderProgramInfoLog) + "");
        }

        glDetachShader(program, shader1);
        glDetachShader(program, shader2);

        bool done = false;

        while(!done)
        {
            SDL_Event event;
            while(SDL_PollEvent(&event))
            {
                switch(event.type)
                {
                case SDL_WINDOWEVENT:
                    switch(event.window.event)
                    {
                    case SDL_WINDOWEVENT_CLOSE:
                        done = true;
                        break;
                    }
                    break;
                }
            }

            glClearColor(0.0, 0.0, 0.0, 1.0);
            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

            glUseProgram(program);

            glBindVertexArray(vao);

            glDrawElements(GL_TRIANGLES,indices.size(),GL_UNSIGNED_SHORT,0);

            glBindVertexArray(0);

            glUseProgram(0);

            SDL_GL_SwapWindow(window);
            }

        glUseProgram(0);
        glDisableVertexAttribArray(0);
        glDisableVertexAttribArray(1);

        glDeleteProgram(program);
        glDeleteBuffers(1, &vbo);
        glDeleteVertexArrays(1, &vao);

        SDL_GL_DeleteContext(context);
        SDL_DestroyWindow(window);
        SDL_Quit();

        std::cout << "all good in the hood" << std::endl;
    }
    catch(const std::exception& e)
    {
        std::cout << "ERROR:\t" << e.what() << std::endl;
    }
    catch(...)
    {
        std::cout << "ERROR" << std::endl;
    }
    exit(EXIT_SUCCESS);
}

我的顶点着色器：

#version 150

precision highp float;

in vec4 in_Position;
in vec3 in_Color;
in vec3 in_Normal;
in vec2 in_UV;

uniform mat4 mvpmatrix;

out vec3 ex_Color;
void main(void) 
{
    gl_Position = in_Position;

    ex_Color = in_Color;
}

我的片段着色器：

#version 150

precision highp float;

in  vec3 ex_Color;
out vec4 gl_FragColor;

void main(void) 
{
    gl_FragColor = vec4(ex_Color,1.0);
}

的 EDIT2

我甚至尝试将一行文本输出到一个文件，然后迭代遍历索引1中的每个三角形1.如果我运行它几次，我发现segfault发生在indices数组中的不同点。索引查找的顶点在我的顶点数组的范围内。

for(int i = 0; i < tt; i+=3)
{
    file << "attempting " << i/3 << std::endl;
    glDrawElements(GL_TRIANGLES,i,GL_UNSIGNED_SHORT,0);
    SDL_GL_SwapWindow(sdlglHandler);
}

所以这告诉我，我试图访问超出我发送到GL_ELEMENT_ARRAY_BUFFER的范围的索引，但是再一次，我看不出问题。

Answer 1

问题在于使用GL_DOUBLE作为顶点。改为GL_FLOAT似乎已经成功了。

使用double时需要使用glVertexAttribLPointer。

有意义地使用glVertexAttribLPointer需要在着色器中重写一行（在dvec4 in_Position中）

Answer 2

您对VAO的使用看起来是正确的。不过，我可以建议您在执行glDrawElements调用之前在索引缓冲区上显式添加glBindBuffer，即

std::shared_ptr<std::vector<GLushort>> p = sphere.GetIndices();
size_t tt = p->size();

glBindVertexArray(vao);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo);
glDrawElements(GL_TRIANGLES,tt,GL_UNSIGNED_SHORT,0);
glBindVertexArray(0);

请注意，即使在今天VAO也没有得到很好的优化，更改VAO绑定可能意味着性能受到影响。 Valve例如对它进行了基准测试，截至目前，它仍然具有在其源引擎中禁用多个VAO的代码路径。在此更改之前，建议的方法是仅绑定缓冲区对象，以及要求VAO在每个上下文中创建和绑定一次的OpenGL配置文件，然后在进一步的操作中忽略它。

glDrawElements中的OpenGL SegFault

大量修改

的 EDIT2

2 个答案: