c++ - 尝试将纹理映射到 GLSL 中的三角形时发生访问冲突

Question

问题在于当我将要绘制的纹理传递给片段着色器时，它是一个 64x64 RGBA 无符号 8 位纹理。我看过其他人的代码，阅读函数定义。使用 glGetError() 检查错误，无论我将它放在程序中的什么位置，它都会返回 0，直到它在调用 glDrawArrays(GL_TRIANGLES, 0, 6); 后抛出访问冲突可能是非常明显的事情，我最近问了一个问题，但我一直在努力自己解决这个问题。所以我希望我不会觉得问这个问题很麻烦。

这是我尝试将纹理加载到内存中的代码

glGenTextures(1, textures);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, textures[0]);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, BTH_IMAGE_WIDTH, BTH_IMAGE_HEIGHT, 0, GL_RGBA, GL_UNSIGNED_BYTE, BTH_IMAGE_DATA);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

这是我尝试将它传递给着色器的地方

GLint texture0 = glGetUniformLocation(gShaderProgram, "texture0");
glUniform1i(texture0, 0);

我的片段着色器

#version 400

out vec4 fragment_color;

uniform sampler2D texture0;

in fData
{
    vec3 normal;
    vec4 color;
    mat4 v;
    vec2 tex_coord;
} frag;



void main () {
    vec3 n = normalize(frag.normal);
    float intensity = min(max(dot(n, vec3(0,0,-1)), 0.0), 1.0);

    //fragment_color = frag.color * (intensity);
    fragment_color = texture(texture0,frag.tex_coord.st) *  intensity;
}

完整的 main.cpp

//--------------------------------------------------------------------------------------
// BTH - Stefan Petersson 2014.
//--------------------------------------------------------------------------------------
#include <vector>
#include <windows.h>
#include <iostream>
#include <string>
#include <fstream>
#include <streambuf>
#include <chrono>
#include <gl/glew.h>
#include <gl/GL.h>
# define M_PI           3.14159265358979323846
#include "glm\glm.hpp"
#include "glm\gtc\matrix_transform.hpp"
#include "bth_image.h"
#pragma comment(lib, "opengl32.lib")
#pragma comment(lib, "glew32.lib")

using namespace std;
using namespace glm;
HWND InitWindow(HINSTANCE hInstance);
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
HGLRC CreateOpenGLContext(HWND wndHandle);

GLuint gVertexBuffer = 0;
GLuint gVertexAttribute = 0;
GLuint gShaderProgram = 0;
GLuint textures[1];
mat4x4 view;
mat4x4 world;
mat4x4 projection;
float DT;

struct CPUvalues
{
    float v1;
    float v2;
    float v3;
    float v4;
};

CPUvalues Gv = { 0.5, 0, 0, 0 };

GLuint gu = 0;

#define BUFFER_OFFSET(i) ((char *)nullptr + (i))

void CreateShaders()
{
    GLuint vs = glCreateShader(GL_VERTEX_SHADER);
    ifstream shaderFile("VertexShader.glsl");
    std::string shaderText((std::istreambuf_iterator<char>(shaderFile)), std::istreambuf_iterator<char>());
    shaderFile.close();
    const char* shaderTextPtr = shaderText.c_str();
    glShaderSource(vs, 1, &shaderTextPtr, nullptr);
    glCompileShader(vs);

    //create fragment shader | same process.
    GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
    shaderFile.open("Fragment.glsl");
    shaderText.assign((std::istreambuf_iterator<char>(shaderFile)), std::istreambuf_iterator<char>());
    shaderFile.close();
    shaderTextPtr = shaderText.c_str();
    glShaderSource(fs, 1, &shaderTextPtr, nullptr);
    glCompileShader(fs);

    GLuint gs = glCreateShader(GL_GEOMETRY_SHADER);
    shaderFile.open("GMshader.glsl");
    shaderText.assign((std::istreambuf_iterator<char>(shaderFile)), std::istreambuf_iterator<char>());
    shaderFile.close();
    shaderTextPtr = shaderText.c_str();
    glShaderSource(gs, 1, &shaderTextPtr, nullptr);
    glCompileShader(gs);

    GLint success = 0;
    glGetShaderiv(gs, GL_COMPILE_STATUS, &success);
    if (success == GL_FALSE)
    {
        GLint logSize = 0;
        glGetShaderiv(gs, GL_INFO_LOG_LENGTH, &logSize);
        std::vector<GLchar> errorLog(logSize);
        glGetShaderInfoLog(gs, logSize, &logSize, &errorLog[0]);
        for (int i = 0; i < errorLog.size(); i++)
        {
            cout << errorLog.at(i);
        }
    }
    //link shader program (connect vs and ps)
    gShaderProgram = glCreateProgram();
    glAttachShader(gShaderProgram, fs);
    glAttachShader(gShaderProgram, gs);
    glAttachShader(gShaderProgram, vs);
    glLinkProgram(gShaderProgram);


    glGenTextures(1, textures);
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, textures[0]);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, BTH_IMAGE_WIDTH, BTH_IMAGE_HEIGHT, 0, GL_RGBA, GL_UNSIGNED_BYTE, BTH_IMAGE_DATA);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);





    GLint isLinked = 0;
    glGetProgramiv(gShaderProgram, GL_LINK_STATUS, &isLinked);
    if (isLinked == GL_FALSE)
    {
        GLint maxLength = 0;
        glGetProgramiv(gShaderProgram, GL_INFO_LOG_LENGTH, &maxLength);
        std::vector<GLchar> infoLog(maxLength);
        glGetProgramInfoLog(gShaderProgram, maxLength, &maxLength, &infoLog[0]);
        for (GLint i = 0; i < maxLength; i++)
        {
            cout << infoLog.at(i);
        }
    }
}

void CreateTriangleData()
{
    // this is how we will structure the input data for the vertex shader
    // every six floats, is one vertex.

    struct TriangleVertex
    {
        float x, y, z;
        float r, g, b;
        float s, t;
    };
    // create the actual data in plane Z = 0
    TriangleVertex triangleVertices[6] = 
    {
        // pos and color for each vertex
        { -0.5f, 0.5f, 0.0f,    1.0f, 0.0f, 0.0f,   1.0f, 0.0f },
        { 0.5f, -0.5f, 0.0f,    0.0f, 1.0f, 0.0f,   0.0f, 1.0f },
        { -0.5f, -0.5f, 0.0f,   0.0f, 0.0f, 1.0f,   1.0f, 0.0f },

        { 0.5f, 0.5f, 0.0f,     0.0f, 0.0f, 1.0f,   1.0f, 0.0f },
        { 0.5f, -0.5f, 0.0f,    0.0f, 1.0f, 0.0f,   0.0f, 1.0f },
        { -0.5f, 0.5f, 0.0f,    1.0f, 0.0f, 0.0f,   1.0f, 0.0f }


    };
    // Vertex Array Object (VAO) 
    glGenVertexArrays(1, &gVertexAttribute);
    // bind == enable
    glBindVertexArray(gVertexAttribute);
    // this activates the first and second attributes of this VAO
    glEnableVertexAttribArray(0); 
    glEnableVertexAttribArray(1);
    glEnableVertexAttribArray(2);

    // create a vertex buffer object (VBO) id
    glGenBuffers(1, &gVertexBuffer);
    // Bind the buffer ID as an ARRAY_BUFFER
    glBindBuffer(GL_ARRAY_BUFFER, gVertexBuffer);
    // This "could" imply copying to the GPU, depending on what the driver wants to do...
    glBufferData(GL_ARRAY_BUFFER, sizeof(triangleVertices), triangleVertices, GL_STATIC_DRAW);

    // query where which slot corresponds to the input vertex_position in the Vertex Shader 
    GLint vertexPos = glGetAttribLocation(gShaderProgram, "vertex_position");
    // specify that: the vertex attribute "vertexPos", of 3 elements of type FLOAT, not normalized, with STRIDE != 0,
    //               starts at offset 0 of the gVertexBuffer (it is implicitly bound!)
    glVertexAttribPointer(vertexPos, 3,    GL_FLOAT, GL_FALSE,     sizeof(TriangleVertex), BUFFER_OFFSET(0));

    // query where which slot corresponds to the input vertex_color in the Vertex Shader 
    //GLint vertexColor = glGetAttribLocation(gShaderProgram, "vertex_color");
    // specify that: the vertex attribute "vertex_color", of 3 elements of type FLOAT, not normalized, with STRIDE != 0,
    //               starts at offset (12 bytes) of the gVertexBuffer 
    //glVertexAttribPointer(vertexColor, 3,    GL_FLOAT, GL_FALSE,     sizeof(TriangleVertex), BUFFER_OFFSET(sizeof(float)*3));

    GLint tex_coord = glGetAttribLocation(gShaderProgram, "coord");
    glVertexAttribPointer(tex_coord,   2,    GL_FLOAT, GL_FALSE,     sizeof(TriangleVertex), BUFFER_OFFSET(sizeof(float)*6));

    //cout << "Error: "<< glGetError() << endl;
}

void SetViewport()
{
    glViewport(0, 0, 640, 480);
}

void Render()
{
    // set the color TO BE used
    glClearColor(0, 0, 0, 1);
    // use the color to clear the color buffer
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);


    glUseProgram(gShaderProgram);
    glBindVertexArray(gVertexAttribute);

    glGenBuffers(1, &gu);
    glBindBuffer(GL_UNIFORM_BUFFER, gu);



    //glBufferSubData(GL_UNIFORM_BUFFER, 0, sizeof(CPUvalues), &Gv);


    GLint _p = glGetUniformLocation(gShaderProgram, "p");
    GLint _m = glGetUniformLocation(gShaderProgram, "m");
    GLint _v = glGetUniformLocation(gShaderProgram, "v");

    //glActiveTexture(GL_TEXTURE0);
    //glBindTexture(GL_TEXTURE_2D, textures[0]);

    GLint texture0 = glGetUniformLocation(gShaderProgram, "texture0");
    glUniform1i(texture0, 0);
    glUniformMatrix4fv(_p, 1, GL_FALSE, &projection[0][0]);
    glUniformMatrix4fv(_m, 1, GL_FALSE, &world[0][0]);
    glUniformMatrix4fv(_v, 1, GL_FALSE, &view[0][0]);


    //GLint texture0 = glGetUniformLocation(gShaderProgram, "texture0");
    //glUniform1i(texture0, GL_TEXTURE0);

    // draw 3 vertices starting from index 0 in the vertex array currently bound (VAO), with current in-use shader
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);
    glFrontFace(GL_CW);
    glCullFace(GL_BACK);
    cout << "Error: " << glGetError() << endl;
    glDrawArrays(GL_TRIANGLES, 0, 6);
}

int WINAPI wWinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmdLine, int nCmdShow )
{
    AllocConsole();
    freopen("CONOUT$", "w", stdout);
    DT = 0.016;
    MSG msg = { 0 };
    HWND wndHandle = InitWindow(hInstance); //1. Skapa fönster
    if (wndHandle)
    {
        HDC hDC = GetDC(wndHandle);

        HGLRC hRC = CreateOpenGLContext(wndHandle); //2. Skapa och koppla OpenGL context

        glewInit(); //3. Initiera The OpenGL Extension Wrangler Library (GLEW)

        SetViewport(); //4. Sätt viewport

        CreateShaders(); //5. Skapa vertex- och fragment-shaders

        CreateTriangleData(); //6. Definiera triangelvertiser, 7. Skapa vertex buffer object (VBO), 8.Skapa vertex array object (VAO)

        ShowWindow(wndHandle, nCmdShow);
        view = lookAt(vec3(0, 0, -2), vec3(0, 0, 0), vec3(0, 1, 0));
        mat4x4 sm;
        sm = scale(sm, vec3(1, 1, 1));
        mat4x4 tm;
        tm = translate(tm, vec3(0, 0, 0));
        mat4x4 rm;
        rm = mat4x4(1);
        projection = perspective<float>(M_PI*0.45, 640 / 480, 0.1, 20);


        while (WM_QUIT != msg.message)
        {
            auto start_time = chrono::high_resolution_clock::now();
            //Gv.v1 += 0.05 * DT;

            Gv.v1 += 1 * DT;
            world = tm * rotate(rm, Gv.v1, vec3(0, 1, 0)) * sm;


            if (PeekMessage(&msg, nullptr, 0, 0, PM_REMOVE))
            {
                TranslateMessage(&msg);
                DispatchMessage(&msg);
            }
            else
            {
                Render(); //9. Rendera
                SwapBuffers(hDC); //10. Växla front- och back-buffer
            }
            auto final_time = chrono::high_resolution_clock::now() - start_time;
            DT = chrono::duration_cast<std::chrono::milliseconds>(final_time).count() / (double)1000;
        }

        wglMakeCurrent(NULL, NULL);
        ReleaseDC(wndHandle, hDC);
        wglDeleteContext(hRC);
        DestroyWindow(wndHandle);
    }

    return (int) msg.wParam;
}

HWND InitWindow(HINSTANCE hInstance)
{
    WNDCLASSEX wcex = { 0 };
    wcex.cbSize = sizeof(WNDCLASSEX); 
    wcex.style          = CS_HREDRAW | CS_VREDRAW;
    wcex.lpfnWndProc    = WndProc;
    wcex.hInstance      = hInstance;
    wcex.lpszClassName = L"BTH_GL_DEMO";
    if( !RegisterClassEx(&wcex) )
        return false;

    RECT rc = { 0, 0, 640, 480 };
    AdjustWindowRect( &rc, WS_OVERLAPPEDWINDOW, FALSE );

    HWND handle = CreateWindow(
        L"BTH_GL_DEMO",
        L"BTH OpenGL Demo",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        rc.right - rc.left,
        rc.bottom - rc.top,
        nullptr,
        nullptr,
        hInstance,
        nullptr);

    return handle;
}

LRESULT CALLBACK WndProc( HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam )
{
    switch (message) 
    {
    case WM_DESTROY:
        PostQuitMessage(0);
        break;      
    }

    return DefWindowProc(hWnd, message, wParam, lParam);
}

HGLRC CreateOpenGLContext(HWND wndHandle)
{
    //get handle to a device context (DC) for the client area
    //of a specified window or for the entire screen
    HDC hDC = GetDC(wndHandle);

    //details: http://msdn.microsoft.com/en-us/library/windows/desktop/dd318286(v=vs.85).aspx
    static  PIXELFORMATDESCRIPTOR pixelFormatDesc =
    {
        sizeof(PIXELFORMATDESCRIPTOR),    // size of this pfd  
        1,                                // version number  
        PFD_DRAW_TO_WINDOW |              // support window  
        PFD_SUPPORT_OPENGL |              // support OpenGL  
        PFD_DOUBLEBUFFER,                 // double buffered        
        PFD_TYPE_RGBA,                    // RGBA type  
        32,                               // 32-bit color depth  
        0, 0, 0, 0, 0, 0,                 // color bits ignored  
        0,                                // no alpha buffer  
        0,                                // shift bit ignored  
        0,                                // no accumulation buffer  
        0, 0, 0, 0,                       // accum bits ignored  
        0,                                // 0-bits for depth buffer <-- modified by Stefan      
        0,                                // no stencil buffer  
        0,                                // no auxiliary buffer  
        PFD_MAIN_PLANE,                   // main layer  
        0,                                // reserved  
        0, 0, 0                           // layer masks ignored  
    };

    //attempt to match an appropriate pixel format supported by a
    //device context to a given pixel format specification.
    int pixelFormat = ChoosePixelFormat(hDC, &pixelFormatDesc);

    //set the pixel format of the specified device context
    //to the format specified by the iPixelFormat index.
    SetPixelFormat(hDC, pixelFormat, &pixelFormatDesc);

    //create a new OpenGL rendering context, which is suitable for drawing
    //on the device referenced by hdc. The rendering context has the same
    //pixel format as the device context.
    HGLRC hRC = wglCreateContext(hDC);

    //makes a specified OpenGL rendering context the calling thread's current
    //rendering context. All subsequent OpenGL calls made by the thread are
    //drawn on the device identified by hdc. 
    wglMakeCurrent(hDC, hRC);

    return hRC;
}

BTH_IMAGE_WIDTH、BTH_IMAGE_HEIGHT 和 BTH_IMAGE_DATA 在 bth_image.h 中定义，以下是其定义的内容(由于 BTH_IMAGE_DATA 较大，将不包括整个定义)

const unsigned int BTH_IMAGE_WIDTH = 64;
const unsigned int BTH_IMAGE_HEIGHT = 64;

//Image data stored in 8-bit RGBA format
unsigned char BTH_IMAGE_DATA[] = {
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,16,16,16,16,16,16,16,16........... 
};

调用 sizeof(BTH_IMAGE_DATA) 得到 16384，它的大小与未压缩的 8 位 64x64 RGBA 编码纹理相匹配(它被硬编码为大学作业的一部分，我对此无能为力)

Answer 1

这次崩溃与纹理无关，而是与您设置顶点属性数组指针的方式有关。

GL 将从您启用的每个数组中获取属性值，并且您在此处为通用顶点属性 0、1 和 2 启用属性数组:

glBindVertexArray(gVertexAttribute);
// this activates the first and second attributes of this VAO
glEnableVertexAttribArray(0); 
glEnableVertexAttribArray(1);
glEnableVertexAttribArray(2);

稍后，您为两个数组设置属性指针:

GLint vertexPos = glGetAttribLocation(gShaderProgram, "vertex_position");
glVertexAttribPointer(vertexPos, 3,    GL_FLOAT, GL_FALSE,     sizeof(TriangleVertex), BUFFER_OFFSET(0));

GLint tex_coord = glGetAttribLocation(gShaderProgram, "coord");
glVertexAttribPointer(tex_coord,   2,    GL_FLOAT, GL_FALSE,     sizeof(TriangleVertex), BUFFER_OFFSET(sizeof(float)*6));

这里有两个错误:

1. 您的第一部分假定 0、1、2 是着色器使用的相关属性索引。由于您从未手动明确分配属性位置(通过顶点着色器代码中的 layout(location=...)，或在链接程序之前通过 glBindAttribLocation，此假设是完全错误。GL 不需要从 0 开始按顺序分配属性位置(尽管大多数情况下如此)，而且您也不能假定任何特定顺序。

2. 您启用了 3 个数组，但只为两个数组设置了一个属性指针。在最好的情况下，其中两个实际上是您启用的两个，在最坏的情况下，它们是完全不同的集合——尽管如此，您仍然至少有一个启用的数组，您从未为其设置指针.默认的顶点指针在客户端内存中只是NULL。因此，您的绘制调用将尝试取消引用 NULL 指针，操作系统将在尝试中终止您的进程，这是应该的。