在90度方位角反轉的圓球相機

Question

我正在嘗試實現一個圓球風格的相機。我使用glm :: lookAt來保持攝像機指向目標，然後使用方位角/傾斜角度將其圍繞球體表面移動以旋轉視圖。

我遇到了一個問題，當方位角接近90度時，視圖會翻轉顛倒。

下面是相關代碼：

1. 獲取投影和視圖martrices。運行在主循環

   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); 
   } 
   

2. 鼠標移動事件，相機旋轉

   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; 
   } 
   

3. 計算相機定向矢量

   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)); 
   } 
   

我敢肯定它的相關我計算相機的正確矢量的方式，但我無法弄清楚如何補償。

有沒有人遇到過這個？有什麼建議麼？

Answer 1

使用lookAt旋轉相機是一個常見的錯誤。你不應該。向後/向右/向上的方向是你的視圖矩陣的列的。如果你已經有了它們，那麼你甚至不需要lookAt，它會嘗試重做一些你的計算。另一方面，lookAt並不能幫助您找到這些載體。

而是從它的列的第一構建視圖矩陣作爲平移和旋轉的組合物，然後提取這些載體：

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); 
    } 
    ... 
} 

然後取出，其計算視圖和從updateModelViewProjection和updateCameraVectors方向矢量的代碼。

聲明：此代碼未經測試。您可能需要在某個地方修正減號，操作順序或慣例可能不匹配（Z上升或Y上升等）。