Question

我无法将图像纹理渲染到屏幕上。除了空白的黑屏外，没有显示任何内容，并且没有明显的错误。我认为这个问题与glOrtho电话有关，但我不确定。

所有相关代码均包含在下方。（在初始化之后和第一次渲染调用之前调用OnResize）

需要OpenGL2.1兼容性，以及稍后添加着色器的视图。纹理内容被硬编码到渲染器只是暂时的，我已经准备好了一个纹理类，一旦我找出了什么是错的。

我想我可能需要一个FrameBuffer对象？我发现的教程经常有很大不同，通常都是针对OGL3

Video::Video() : running(true)
{
    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        std::string err = "Error initialising video: ";
        err += SDL_GetError();
        throw std::runtime_error(err);
    }

    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);
    SDL_GL_SetAttribute(SDL_GL_ACCELERATED_VISUAL, 1);
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);

    int flags = SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_MAXIMIZED;

    this->window = SDL_CreateWindow("lolpenGL", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 800, 600, flags);
    if (this->window == nullptr) {
        std::string err = "Error creating SDL window: ";
        err += SDL_GetError();
        throw std::runtime_error(err);
    }

    this->glcontext = SDL_GL_CreateContext(this->window);
    if (this->glcontext == nullptr) {
        std::string err = "Error creating GL context: ";
        err += SDL_GetError();
        throw std::runtime_error(err);
    }

    GLenum glew_err = glewInit();
    if (glew_err != GLEW_OK) {
        std::string err = "Error initialising GLEW: ";
        err += (char *)glewGetErrorString(glew_err);
        throw std::runtime_error(err);
    }

    if (!GLEW_VERSION_2_1) {
        throw std::runtime_error("OpenGL 2.1 not available");
    }

    int max_tex_size;
    glGetIntegerv(GL_MAX_TEXTURE_SIZE, &max_tex_size);
    if (max_tex_size < 1024) {
        throw std::runtime_error("Maximum supported texture size too small");
    }

    int max_tex_units;
    glGetIntegerv(GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS, &max_tex_units);
    if (max_tex_units < 2) {
        throw std::runtime_error("GPU does not have enough texture unnits");
    }

    SDL_GL_SetSwapInterval(1); // vsync

    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    glDisable(GL_DEPTH_TEST); // what's drawn last is displayed on top.




// Temp texture load
        glGenTextures(1, &this->texid);
        glBindTexture(GL_TEXTURE_2D, this->texid);
        // Set our texture parameters
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
        // Set texture filtering
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        // Load, create texture and generate mipmaps
        int width, height;
        unsigned char *image = SOIL_load_image("awesomeface.png", &width, &height, 0, SOIL_LOAD_RGB);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
        glGenerateMipmap(GL_TEXTURE_2D);
        SOIL_free_image_data(image);
        glBindTexture(GL_TEXTURE_2D, 0);

        glEnable(GL_TEXTURE_2D);
}

void Video::OnResize(int w, int h)
{
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    glViewport(0, 0, w, h);

    glOrtho(0, w, 0, h, 9001, -1);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

void Video::Render()
{
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);

    glPushMatrix();
    {
        glColor4f(1, 1, 1, 1);
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, this->texid);
        // do stuff
    }
    glPopMatrix();


    SDL_GL_SwapWindow(this->window);
}

编辑：好的，我是个白痴，我实际上并没有画任何东西。我发现添加以下作品，// do stuff是。

glBegin(GL_QUADS);
glTexCoord2f(0, 0); glVertex3f(0, 0, 0);
glTexCoord2f(0, 1); glVertex3f(0, 100, 0);
glTexCoord2f(1, 1); glVertex3f(100, 100, 0);
glTexCoord2f(1, 0); glVertex3f(100, 0, 0);
glEnd();

这是最好的方法吗？

获取OpenGL将纹理渲染到屏幕

0 个答案: