使用 GLM 正确旋转 Open GL 相机答案

【问题标题】：Rotating a Open GL camera correctly using GLM使用 GLM 正确旋转 Open GL 相机
【发布时间】：2012-08-27 08:40:43
【问题描述】：

我有一个相机类，它是这样初始化的：

CameraFP::CameraFP()  {
    this->aspect_ratio = 800.0f / 600.0f;
    this->fov = 45.0f;
    this->near_plane = 0.1f;
    this->far_plane = 1000.0f;
    this->position = glm::vec3(0, 0, 0);
    this->target = position + glm::vec3(0, 0, -1);
    this->up = glm::vec3(0, 1, 0);
    this->m_rotation = glm::mat4(1.0);

    m_view = glm::lookAt(position, target, up);
    m_projection = glm::perspective(fov, aspect_ratio, near_plane, far_plane);
}

还有其他导入功能：

void CameraFP::update(sf::Window *app)  {
    process_keyboard(app);
    process_mouse(app);

    calculate_view();
}

void CameraFP::process_keyboard(sf::Window *app)  {
    const sf::Input *input = &app->GetInput();

    up = m_rotation * glm::vec3(0, 1, 0);

    glm::vec3 forward = glm::vec3(0, 0, -1);
    glm::vec3 forward_rotated = m_rotation * forward;

    glm::vec3 right = glm::vec3(1, 0, 0);
    glm::vec3 right_rotated = m_rotation * right;

    if (input->IsKeyDown(sf::Key::W))  {
        position += forward_rotated;
    }
    if (input->IsKeyDown(sf::Key::S))  {
        position -= forward_rotated;
    }
    if (input->IsKeyDown(sf::Key::A))  {
        position -= right_rotated;
    }
    if (input->IsKeyDown(sf::Key::D))  {
        position += right_rotated;
    }
}

void CameraFP::process_mouse(sf::Window *app)  {
    // TODO: Make the below constants, and take framerate into account
    GLfloat SPEED_X = 0.000001f;
    GLfloat SPEED_Y = 0.000001f;

    GLfloat mouse_x = app->GetInput().GetMouseX();
    GLfloat mouse_y = app->GetInput().GetMouseY();

    GLfloat mouse_x_delta = old_mouse_x - mouse_x;
    GLfloat mouse_y_delta = old_mouse_y - mouse_y;

    if (mouse_x_delta != 0 ||
        mouse_y_delta != 0)  {
        if (mouse_x_delta != 0)  {
            y_rot += mouse_x_delta * SPEED_X;

            m_rotation = glm::rotate(m_rotation, y_rot, glm::vec3(0, 1, 0));
        }
        if (mouse_y_delta != 0)  {
            x_rot += mouse_y_delta * SPEED_Y;

            m_rotation = glm::rotate(m_rotation, x_rot, glm::vec3(1, 0, 0));;
        }
    }

    this->old_mouse_x = mouse_x;
    this->old_mouse_y = mouse_y;

    app->SetCursorPosition(app->GetWidth() / 2, app->GetHeight() / 2);
}


void CameraFP::calculate_view()  {
    glm::vec3 forward = glm::vec3(0, 0, -1);
    glm::vec3 forward_rotated = m_rotation * forward;

    target = position += glm::normalize(forward_rotated);

    m_view = glm::lookAt(position, target, up);
}

我的问题是，当我编译项目时，编译器输出一个错误说：

\CameraFP.cpp|59|error: no match for 'operator*' in '((CameraFP*)this)->CameraFP::m_rotation * glm::detail::tvec3<float>(((const int&)((const int*)(&0))), ((const int&)((const int*)(&1))), ((const int&)((const int*)(&0))))'|

据我了解 vec = mat4 * vec 应该产生一个旋转向量？由于无法测试这段代码，不知道功能是否正常。

编辑

根据 cmets 和 awnsers 更新了代码。我现在的问题是我在渲染函数的某个地方得到了一个 BSOD...

void CameraFP::process_keyboard(sf::Window *app)  {
    const sf::Input *input = &app->GetInput();

    up = m_rotation * glm::vec4(0.0f, 1.0f, 0.0f, 0.0f);

    glm::vec4 forward = glm::vec4(0.0f, 0.0f, -1.0f, 0.0f);
    glm::vec4 forward_rotated = m_rotation * forward;

    glm::vec4 right = glm::vec4(1.0f, 0.0f, 0.0f, 0.0f);
    glm::vec4 right_rotated = m_rotation * right;

    if (input->IsKeyDown(sf::Key::W))  {
        position += forward_rotated;
    }
    if (input->IsKeyDown(sf::Key::S))  {
        position -= forward_rotated;
    }
    if (input->IsKeyDown(sf::Key::A))  {
        position -= right_rotated;
    }
    if (input->IsKeyDown(sf::Key::D))  {
        position += right_rotated;
    }
}

void CameraFP::process_mouse(sf::Window *app)  {
    // TODO: Make the below constants, and take framerate into account
    GLfloat SPEED_X = 0.000001f;
    GLfloat SPEED_Y = 0.000001f;

    GLfloat mouse_x = app->GetInput().GetMouseX();
    GLfloat mouse_y = app->GetInput().GetMouseY();

    GLfloat mouse_x_delta = old_mouse_x - mouse_x;
    GLfloat mouse_y_delta = old_mouse_y - mouse_y;

    if (mouse_x_delta != 0 ||
        mouse_y_delta != 0)  {
        if (mouse_x_delta != 0)  {
            y_rot += mouse_x_delta * SPEED_X;

            m_rotation = glm::rotate(m_rotation, y_rot, glm::vec3(0.0f, 1.0f, 0.0f));
        }
        if (mouse_y_delta != 0)  {
            x_rot += mouse_y_delta * SPEED_Y;

            m_rotation = glm::rotate(m_rotation, x_rot, glm::vec3(1.0f, 0.0f, 0.0f));;
        }
    }

    this->old_mouse_x = mouse_x;
    this->old_mouse_y = mouse_y;

    app->SetCursorPosition(app->GetWidth() / 2, app->GetHeight() / 2);
}

void CameraFP::calculate_view()  {
    glm::vec4 forward = glm::vec4(0.0f, 0.0f, -1.0f, 0.0f);
    glm::vec4 forward_rotated = m_rotation * forward;

    target = position += forward_rotated;

    m_view = glm::lookAt(v4tov3(position), v4tov3(target), v4tov3(up));
}

glm::vec3 v4tov3(glm::vec4 v1)  {
    return glm::vec3(v1.x, v1.y, v1.z);
}

编辑 2

现在的问题是用鼠标旋转相机，它只是不起作用，由于某种原因，x 轴上的变化经常影响 y 轴上的变化，反之亦然。此外，如果我在 x 轴（y 旋转）上向右或向左移动鼠标，相机将向左旋转...

void CameraFP::process_mouse(sf::Clock *clock, sf::Window *app)  {
    // TODO: Make the below constants, and take framerate into account
    GLfloat SPEED_X = 0.25f;
    GLfloat SPEED_Y = 0.25f;

    GLfloat screen_x = app->GetWidth();
    GLfloat screen_y = app->GetHeight();

    GLfloat mouse_x = float(screen_x / 2 - app->GetInput().GetMouseX());
    GLfloat mouse_y = float(screen_y / 2 - app->GetInput().GetMouseY());

    GLfloat mouse_x_delta = old_mouse_x - mouse_x;
    GLfloat mouse_y_delta = old_mouse_y - mouse_y;

    GLfloat current_time = clock->GetElapsedTime();
    GLfloat delta_time = current_time - last_time;

    this->last_time = current_time;

    if (mouse_x_delta != 0 ||
        mouse_y_delta != 0)  {
        if (mouse_x_delta != 0)  {
            y_rot += glm::radians(delta_time * SPEED_X * mouse_x);

            m_rotation = glm::rotate(m_rotation, y_rot, glm::vec3(0.0f, 1.0f, 0.0f));

            std::cout << "Y Rotation: " << y_rot << "\n";
        }
        if (mouse_y_delta != 0)  {
            x_rot += glm::radians(delta_time * SPEED_Y * mouse_y);

            m_rotation = glm::rotate(m_rotation, x_rot, glm::vec3(1.0f, 0.0f, 0.0f));

            std::cout << "X rotation: " << x_rot << "\n";
        }
    }

    app->SetCursorPosition(screen_x / 2, screen_y / 2);

    this->old_mouse_x = float(screen_x / 2 - app->GetInput().GetMouseX());
    this->old_mouse_y = float(screen_y / 2 - app->GetInput().GetMouseY());
}

【问题讨论】：

未找到 mat4*vec3 的运算符 *。 m_rotation 是 mat4，forward 是 vec3。我认为应该是vec4。
@AquilaRapax 但是，我不是打算将位置表示为 vec3s 吗？我认为我不应该一直在 glm::vec3 和 glm::vec4 之间进行转换。我应该使用 glm::mat3 来表示我的旋转吗？
通常使用齐次坐标，因此所有向量和矩阵的维度都是 4。对于向量，最后一个坐标称为 w-coordinate 并且必须为 1。所以你不需要将 vec3 转换为 vec4。只需使用 vec4 并将第 4 个坐标设置为 1。有关更多信息，请查看 en.wikipedia.org/wiki/Homogeneous_coordinates

标签： c++ opengl matrix camera glm-math

【解决方案1】：

替换所有 glm::vec3(0, 1, 0);通过 glm::vec3(0.0f, 1.0f, 0.0f);

至于 vec-mac 乘法，AquilaRapax 是正确的，因为您只能将 mat4 与 vec4 相乘。但是由于您要乘以方向，因此第 4 个坐标应该是 0.0f，而不是 1.0f。这将产生忽略翻译的效果（1.0 会将它们考虑在内，这是您不想要的）

有关矩阵的详细信息，请参阅http://www.opengl-tutorial.org/beginners-tutorials/tutorial-3-matrices/。

但是，保留 vec3 而不是 vec4 通常是个好主意，主要是为了清楚起见（即，使用 glm::vec3 mPosition 而不是 glm::vec4 mPosition）。因此，拥有 2 个这样的功能（未经测试）很方便：

glm::vec3 TransformDirection(glm::vec3 pDirection, glm::mat4 pMatrix){
    return pMatrix * glm::vec4(pDirection, 0.0f);
}

glm::vec3 TransformPosition(glm::vec3 pDirection, glm::mat4 pMatrix){
    return pMatrix * glm::vec4(pDirection, 1.0f);
}

【讨论】：

@Calvin1602 所以我必须将我的位置（以及我所有的其他向量）设为 vec4？例如，由于我需要通过旋转矩阵变换前向向量，因此我需要将旋转后的向量应用于位置。对于方向，我必须将 0.0f 作为最后一个参数，对于位置和目标，1.0f？
@Calvin1602 例如。在 calculate_view 函数中，我将不得不这样做：pastebin.com/6F0gh8dG ...我的计算机在运行时崩溃：|
@Calvin1602 哇！它不会给我蓝屏！谢谢...我现在的问题似乎是鼠标，无论我在x轴上向哪个方向移动鼠标我总是向右转，无论我在y轴上向哪个方向移动鼠标，它总是向下看.. . 嗯...
查看编辑。对于鼠标： old_mouse 是错误的。将其完全删除并改用尺寸/2。或者删除 SetCursorPosition()。
@Calvin1602 好的，完成了。我现在更加困惑，因为当我向左移动鼠标时，它会向右移动！当我向右移动时，它会向下移动相机……我真的很困惑……pastebin.com/PyVYC9X1

【解决方案2】：

在process::mouse 的末尾，您将坐标保存在old_mouse_x 和old_mouse_y 中，然后将光标移动到屏幕中间。如果您这样做，old_mouse_x 和 old_mouse_y 将无效。您需要做的是在重新定位光标后设置这些变量：

app->SetCursorPosition(app->GetWidth() / 2, app->GetHeight() / 2);
this->old_mouse_x = app->GetWidth() / 2;
this->old_mouse_y = app->GetHeight() / 2;

【讨论】：