我的OpenGL和SDL2代码有什么问题

What is wrong with my OpenGL with SDL2 code?

本文关键字:什么 问题 代码 SDL2 OpenGL 我的      更新时间:2023-10-16

我无法绘制到使用以下代码创建的窗口。

我所知道的是正确的:

  • sdl2初始化
  • glew初始化
  • 窗口创建
  • 上下文创建

我认为可能是问题所在:

  • glsl着色器,但它们正在成功编译
  • glVertexAttribPointer()
  • 缺少函数调用

我已经排除了错误检查的可能性:

  • sdl初始化
  • glew初始化
  • 窗口创建
  • 上下文创建
  • 顶点着色器编译
  • 片段着色器编译
  • 程序链接

注意:我已经编写了我的着色器内联(glsl.h).

main.cpp

    #include <GLglew.h>
    #include <SDL.h>
    #include <glmglm.hpp>
    #include <iostream>
    #include "glsl.h"
    #define SDL_INIT_FAIL -1
    #define IMAGE_INIT_FAIL 0
    #define glsl(version, glsl) "#version " #version "n" #glsl
    namespace glsl { namespace vs {
    //VERTEX SHADERS
    //=========================
    // simple VS
    //=========================
    constexpr GLchar * const simple = glsl(450 core, 
        layout(location = 0) in vec3 position;
        void main() {
            gl_Position = vec4(position, 1.0f);
        }
        );
    } namespace fs {
    //FRAGMENT SHADERS
    //=========================
    // simple FS
    //=========================
    constexpr GLchar * const simple = glsl(450 core,
        out vec4 color;
        void main() {
            color = vec4(1.0f, 0.0f, 0.0f, 1.0f);
        }       
        );
} }
    constexpr GLint image_Flags{ IMG_INIT_PNG | IMG_INIT_JPG };
    constexpr GLuint init_Flags{ SDL_INIT_VIDEO | SDL_INIT_EVENTS },window_Flags{ SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE};
    constexpr GLchar * window_Title{ "Sprite Game with OpenGL" };
    constexpr GLint window_Width{ 1200 }, window_Height{ 740 }, window_PositionX{ SDL_WINDOWPOS_CENTERED },
        window_PositionY{ SDL_WINDOWPOS_CENTERED };
    int main(int argc, char * argv[]) {
        std::cout << glsl::vs::simple << std::endl << std::endl;
    std::cout << glsl::fs::simple << std::endl << std::endl;
    system("pause");
    if (SDL_Init(init_Flags) == SDL_INIT_FAIL) {
        std::cerr << "error init sdl" << std::endl;
        return 1;
    }
    SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_BUFFER_SIZE, 32);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 23);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 5);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
    SDL_Window * window = nullptr;
    window = SDL_CreateWindow(window_Title, window_PositionX, window_PositionY, window_Width, window_Height, window_Flags);
    if (window == nullptr) {
         std::cerr << "error window is nullptr" << std::endl;
        SDL_Quit();
        return 4;
    }
    SDL_GLContext context = nullptr;
    context = SDL_GL_CreateContext(window);
    if (context == nullptr) {
        std::cerr << "error context is nullptr" << std::endl;
        SDL_DestroyWindow(window);
        window = nullptr;
        SDL_Quit();
        return 5;
    }
    glewExperimental = true;
    GLenum glewError = glewInit();
    if (glewError != GLEW_OK) {
        std::cerr << "error glew init: " << glewGetErrorString(glewError) << std::endl;
        SDL_Quit();
        return 3;
    }
    std::cout << "OpenGL Version " << glGetString(GL_VERSION) << std::endl;
    struct Mouse
    {
        Uint32 mouseState = 0;
        GLint mx{ 0 }, my{ 0 };
    };
    struct Input {
        Mouse mouse;
        SDL_Event e;
        const Uint8 * keyState = nullptr;
    } input;
    struct Shader {
        GLuint program;
        GLuint vertexShader;
        GLuint fragmentShader;
    } shader;
    shader.vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(shader.vertexShader, 1, &glsl::vs::simple, NULL);
    glCompileShader(shader.vertexShader);
    GLint vertexCompilei;
    GLchar vsiInfo[512];
    glGetShaderiv(shader.vertexShader, GL_COMPILE_STATUS, &vertexCompilei);
    if (vertexCompilei == GL_FALSE) {
        glGetShaderInfoLog(shader.vertexShader, sizeof vsiInfo, NULL, vsiInfo);
        std::cerr << vsiInfo << std::endl;
    }
    shader.fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(shader.fragmentShader, 1, &glsl::fs::simple, NULL);
    glCompileShader(shader.fragmentShader);
    GLint fragmentCompilei;
    GLchar fsiInfo[512];
    glGetShaderiv(shader.fragmentShader, GL_COMPILE_STATUS, &fragmentCompilei);
    if (fragmentCompilei == GL_FALSE) {
        glGetShaderInfoLog(shader.fragmentShader, sizeof fsiInfo, NULL, fsiInfo);
        std::cerr << fsiInfo << std::endl;
    }
    shader.program = glCreateProgram();
    glAttachShader(shader.program, shader.vertexShader);
    glAttachShader(shader.program, shader.fragmentShader);
    glLinkProgram(shader.program);
    GLint programLinki;
    GLchar programInfo[512];
    glGetProgramiv(shader.program, GL_LINK_STATUS, &programLinki);
    if (programLinki == GL_FALSE) {
        glGetProgramInfoLog(shader.program, sizeof programInfo, NULL, programInfo);
        std::cerr << programInfo << std::endl;
    }

    struct Object {
        GLuint VAO;
        GLuint VBO;
    } object;
    GLfloat vertices[] = {
        -0.5f, -0.5f, 0.0f,
         0.5f, -0.5f, 0.0f,
         0.0f,  0.5f, 0.0f
    };
    glGenVertexArrays(1, &object.VAO);
    glGenBuffers(1, &object.VBO);
    glBindVertexArray(object.VAO);
    glBindBuffer(GL_ARRAY_BUFFER, object.VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof vertices, vertices, GL_STATIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof GLfloat * 3, (GLvoid*)0);
    glBindVertexArray(0);
    glEnable(GL_DEPTH_TEST);
    do {
        glViewport(0, 0, window_Width, window_Height);
        glClearColor(0.3f, 0.1f, 0.1f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
        glUseProgram(shader.program);
        glBindVertexArray(object.VAO);
        glDrawArrays(GL_TRIANGLES, 0, 3);
        glBindVertexArray(0);
        glUseProgram(0);
        SDL_GL_SwapWindow(window);
        SDL_PollEvent(&input.e);
        input.keyState = SDL_GetKeyboardState(0);
        input.mouse.mouseState = SDL_GetMouseState(&input.mouse.mx, &input.mouse.my);
    } while (!input.keyState[SDL_SCANCODE_ESCAPE] && input.e.type != SDL_QUIT);

    glDeleteShader(shader.vertexShader);
    glDeleteShader(shader.fragmentShader);
    glDeleteProgram(shader.program);
    SDL_GL_DeleteContext(context);
    context = nullptr;
    SDL_DestroyWindow(window);
    window = nullptr;
    SDL_Quit();
    return 0;
    }

深度测试把它搞砸了。这是由注释代码直到其工作为止的老方法发现的。当然,当您调试空白屏幕错误时,这并不总是有效的。

为什么搞砸了?因为使用glClear(GL_COLOR_BUFFER_BIT | GL_COLOR_BUFFER_BIT);,您似乎粘贴错误,并且没有清除深度缓冲区,因此后续的三角形无法通过默认的深度测试(在不设置深度函数的情况下启用深度测试是很奇怪的)。