Question

我正在尝试实施一个弧形风格的相机。我使用glm :: lookAt让相机指向目标，然后使用方位角/倾斜角度围绕球体表面移动它来旋转视图。

我遇到了一个问题，当方位角接近90度时，视图会颠倒翻转。

以下是相关代码：

获取投影并查看好消息。在主循环中运行

void Visual::updateModelViewProjection()
{
    model = glm::mat4();
    projection = glm::mat4();
    view = glm::mat4();

    projection = glm::perspective
        (
        (float)glm::radians(camera.Zoom),
        (float)width / height, // aspect ratio
        0.1f, // near clipping plane
        10000.0f // far clipping plane
        );

    view = glm::lookAt(camera.Position, camera.Target, camera.Up);
}

鼠标移动事件，用于相机旋转

void Visual::cursor_position_callback(GLFWwindow* window, double xpos, double ypos)
{
    if (leftMousePressed)
    {
       ...
    }

    if (rightMousePressed)
    {
        GLfloat xoffset = (xpos - cursorPrevX) / 4.0;
        GLfloat yoffset = (cursorPrevY - ypos) / 4.0;

        camera.inclination += yoffset;
        camera.azimuth -= xoffset;
        if (camera.inclination > 89.0f)
            camera.inclination = 89.0f;
        if (camera.inclination < 1.0f)
            camera.inclination = 1.0f;

        if (camera.azimuth > 359.0f)
            camera.azimuth = 359.0f;
        if (camera.azimuth < 1.0f)
            camera.azimuth = 1.0f;

        float radius = glm::distance(camera.Position, camera.Target);
        camera.Position[0] = camera.Target[0] + radius * cos(glm::radians(camera.azimuth)) * sin(glm::radians(camera.inclination));
        camera.Position[1] = camera.Target[1] + radius * sin(glm::radians(camera.azimuth)) * sin(glm::radians(camera.inclination));
        camera.Position[2] = camera.Target[2] + radius * cos(glm::radians(camera.inclination));

        camera.updateCameraVectors();
    }

    cursorPrevX = xpos;
    cursorPrevY = ypos;
}

计算相机方向矢量

void updateCameraVectors()
{
    Front = glm::normalize(Target-Position);
    Right = glm::rotate(glm::normalize(glm::cross(Front, {0.0, 1.0, 0.0})), glm::radians(90.0f), Front);
    Up = glm::normalize(glm::cross(Front, Right));
}

我很确定这与我计算相机右侧矢量的方式有关，但我无法弄清楚如何补偿。

有没有人遇到过这个？有什么建议？

Answer 1

使用lookAt旋转相机是一个常见的错误。你不应该。向后/向右/向上方向是视图矩阵的列。如果您已经拥有它们，那么您甚至不需要lookAt，它会尝试重做您的一些计算。另一方面，lookAt并不能帮助您首先找到这些向量。

首先将视图矩阵构建为翻译和旋转的组合，然后从其列中提取这些向量：

void Visual::cursor_position_callback(GLFWwindow* window, double xpos, double ypos)
{
    ...
    if (rightMousePressed)
    {
        GLfloat xoffset = (xpos - cursorPrevX) / 4.0;
        GLfloat yoffset = (cursorPrevY - ypos) / 4.0;

        camera.inclination = std::clamp(camera.inclination + yoffset, -90.f, 90.f);
        camera.azimuth = fmodf(camera.azimuth + xoffset, 360.f);

        view = glm::mat4();
        view = glm::translate(view, glm::vec3(0.f, 0.f, camera.radius)); // add camera.radius to control the distance-from-target
        view = glm::rotate(view, glm::radians(camera.inclination + 90.f), glm::vec3(1.f,0.f,0.f));
        view = glm::rotate(view, glm::radians(camera.azimuth), glm::vec3(0.f,0.f,1.f));
        view = glm::translate(view, camera.Target);

        camera.Right = glm::column(view, 0);
        camera.Up = glm::column(view, 1);
        camera.Front = -glm::column(view, 2); // minus because OpenGL camera looks towards negative Z.
        camera.Position = glm::column(view, 3);

        view = glm::inverse(view);
    }
    ...
}

然后从updateModelViewProjection和updateCameraVectors中删除计算视图和方向向量的代码。

免责声明：此代码未经测试。您可能需要在某处修改减号，操作顺序或约定可能不匹配（Z为up或Y为up等等）。

弧球相机以90度方位角反转

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