无法使FreeType呈现

Question

使用OpenGL，GLM，GLAD，GLFW和FreeType尝试获得字体渲染。我已经确保在渲染时没有发生OpenGL错误，没有发布错误代码，但是没有渲染到屏幕上。我也不确定我是否正确地使用了glm的正交函数，因为我不确定在哪里实际使用该变量：

glm::mat4 projection = glm::ortho(0.0f, 800.0f, 0.0f, 600.0f);

这是我的绘制循环，它在场景初始化后调用：

void GameLoop::Run()
{
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glClearColor(0.2f, 0.3f, 0.3f, 1.0f);

    while (!glfwWindowShouldClose(m_game_window))
    {
        // Do That thing where you draw everything
    }
}

将字体加载到纹理中的Font构造函数：

Salem::Graphics::Font::Font(std::string p_font_path)
{
    FT_Library ft;
    if (FT_Init_FreeType(&ft))
    {
        std::cout << "Error loading FreeType library" << std::endl;
    }

    FT_Face face;
    if (FT_New_Face(ft, p_font_path.c_str(), 0, &face))
    {
        std::cout << "Error loading font;\n" << p_font_path << std::endl;
    }

    FT_Set_Pixel_Sizes(face, 0, 28);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1); // Disable byte-alignment restriction

    for (GLubyte c = 0; c < 128; c++)
    {
        if (FT_Load_Char(face, c, FT_LOAD_RENDER))
        {
            std::cout << "Failed to load a character glyph." << std::endl;
            continue;
        }

        GLuint texture;
        glGenTextures(1, &texture);
        glBindTexture(GL_TEXTURE_2D, texture);
        glTexImage2D(
                GL_TEXTURE_2D,
                0,
                GL_RED,
                face->glyph->bitmap.width,
                face->glyph->bitmap.rows,
                0,
                GL_RED,
                GL_UNSIGNED_BYTE,
                face->glyph->bitmap.buffer);

        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);

        Character character = {
                texture,
                glm::ivec2(face->glyph->bitmap.width, face->glyph->bitmap.rows),
                glm::ivec2(face->glyph->bitmap_left, face->glyph->bitmap_top),
                face->glyph->advance.x
        };

        m_characters.insert(std::make_pair(c, character));
    }

    FT_Done_Face(face);
    FT_Done_FreeType(ft);
    std::cout << "Font loaded. " << std::endl;
}

My text的初始化函数：

void Text::Initialize()
{
    glm::mat4 projection = glm::ortho(0.0f, 800.0f, 0.0f, 600.0f);
    glGenVertexArrays(1, &m_vao);
    glGenBuffers(1, &m_vbo);

    glBindVertexArray(m_vao);
    glBindBuffer(GL_ARRAY_BUFFER, m_vbo);

    glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 6 * 4, nullptr, m_draw_method);

    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), nullptr);

    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);
}

和我的文本的绘图函数：

void Text::Draw()
{
    glm::mat4 projection = glm::ortho(0.0f, 800.0f, 0.0f, 600.0f);

    shader()->Use();
    glUniform3f(glGetUniformLocation(shader()->id(), "textColor"), m_color.x, m_color.y, m_color.z);
    glActiveTexture(GL_TEXTURE0);
    glBindVertexArray(m_vao);

    for (std::string::const_iterator c = m_text.begin(); c != m_text.end(); ++c)
    {
        Character ch = m_font.characters()[*c];

        GLfloat xPosition = m_position.x + ch.Bearing.x * m_scale;
        GLfloat yPosition = m_position.y - (ch.Size.y - ch.Bearing.y) * m_scale;

        GLfloat width = ch.Size.x * m_scale;
        GLfloat height = ch.Size.y * m_scale;

        GLfloat vertices[6][4] = {
                {xPosition,         yPosition + height, 0.0, 0.0},
                {xPosition,         yPosition,          0.0, 1.0},
                {xPosition + width, yPosition,          1.0, 1.0},

                {xPosition,         yPosition + height, 0.0, 0.0},
                {xPosition + width, yPosition,          1.0, 1.0},
                {xPosition + width, yPosition + height, 1.0, 0.0}
        };

        glBindTexture(GL_TEXTURE_2D, ch.TextureID);
        glBindBuffer(GL_ARRAY_BUFFER, m_vbo);
        glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices);
        //glBindBuffer(GL_ARRAY_BUFFER, 0);

        glDrawArrays(GL_TRIANGLES, 0, 6);

        m_position.x += (ch.Advance >> 6) * m_scale;
    }

    glBindVertexArray(0);
    glBindTexture(GL_TEXTURE_2D, 0);
}

不希望文章太长，如果需要我的着色器，请让我知道。

Answer 1

分解代码后，我发现了一个有用的资源，它将我引向了我的问题。从https://learnopengl.com/#!In-Practice/Text-Rendering项目源代码中，我发现我的正交投影变量必须在我构造字体时传递给我的着色器程序。我通过将以下代码添加到我的Font构造函数中来完成此操作：

glm::mat4 projection = glm::ortho(0.0f, 800.0f, 0.0f, 600.0f);
p_shader->Use();
glUniformMatrix4fv(glGetUniformLocation(p_shader->id(), "projection"), 1, GL_FALSE, glm::value_ptr(projection));