OpenTK/OpenGL的 - 旋轉的攝像頭，鼠標

Question

背景

目前，我有我顯示，將永遠是在原點的對象。我有我的遞增x和y的角度，然後計算出新的X，Y的函數，Z爲攝像機座標：

Public Sub update_rotation() 
    If cam.manual_lookat = True Then 
     If camangley >= 360 Then 
      camangley = camangley - 360 
     End If 

     If camanglex >= 360 Then 
      camanglex = camanglex - 360 
     End If 

     If camangley < 0 Then 
      camangley = 360 + camangley 
     End If 

     If camanglex < 0 Then 
      camanglex = 360 + camanglex 
     End If 

     If camangley > 90 And camangley <= 270 Then 
      cam.invert_y = True 
     Else 
      cam.invert_y = False 
     End If 


     camx = distance * -Sin(camanglex * (PI/180)) * Cos((camangley) * (PI/180)) 

     camy = distance * -Sin((camangley) * (PI/180)) 

     camz = distance * Cos((camanglex) * (PI/180)) * Cos((camangley) * (PI/180)) 

     cam.Position.X = camx 
     cam.Position.Y = camy 
     cam.Position.Z = camz 
     cam.lookat.X = 0 
     cam.lookat.Y = 0 
     cam.lookat.Z = 0 

     ' Label2.Text = camanglex & "," & camangley 
    End If 

End Sub 

我有這樣的設置爲使用鍵盤事件.. X按鈕添加到camanglex變量，Y按鈕添加到camangley變量，Z按鈕添加到距離變量。

一切正常，這樣做，使用鍵盤。

問題

我想現在使用鼠標來處理旋轉，而不是鍵盤。我相信這只是一個數學問題，但我該如何計算新的camanglex和camangley變量，或者直接計算新的camx，camy，camz以建立我的相機新位置？

我有一個鼠標功能，它將捕捉鼠標座標，但我有計算部分的麻煩。

Answer 1

如果你想圍繞物體轉動，你可以追蹤你的鼠標在假球上的路徑（有時稱爲跟蹤球）。有a working example of orbit controls。

這裏是類似的東西的僞草圖：

mouseDownEventFunction(event) { 
    computeDragPoint (event.mouseX, event.mouseY, &oldDragPoint); 
    isMouseDown = true; 
} 
mouseUpEventFunction(event) { 
    isMouseDown = false; 
} 
mouseMoveEventFunction(event) { 
    if (isMouseDown) { 
     computeDragPoint (event.mouseX, event.mouseY, &newDragPoint); 
     rotateCamera (oldDragPoint, newDragPoint); 
     oldDragPoint = newDragPoint; 
    } 
} 

在這裏，我們找到軌跡球點：

/* we want to ray trace a point on face side of fake sphere. 
dragPoint* is our result*/ 

computeDragPoint(int x, int y, Vector3* dragPoint) { 
    /* normalize x and y to [-1, 1] so they match flat circle position on screen. 
    And assign this to dragPoint->x and dragPoint->y. 
    This part depends on what you want to achieve and input units of x, y. 
    Keep in mind aspect ratio */ 
    dragPoint->x = (2*x/screenWidth - 0.5) * (screenHeight/screenWidth); 
    dragPoint->y = 2*y/screenHeight - 0.5; 
    dragPoint->x /= sqrt(dragPoint->x*dragPoint->x + dragPoint->y*dragPoint->y); 
    dragPoint->y /= sqrt(dragPoint->x*dragPoint->x + dragPoint->y*dragPoint->y); 

    /* Then having two values in [-1,1] compute corresponding z */ 
    float tmp = dragPoint->x*dragPoint->x + dragPoint->y*dragPoint->y; 
    if (tmp > 1) { 
     dragPoint.x /= sqrt(tmp); 
     dragPoint.y /= sqrt(tmp); 
    } 

    dragPoint->z = -sqrt (1 - dragPoint->x^2 - dragPoint->y^2) || 0; 
} 

和旋轉的數學可以用四元數來完成（或者從歐拉只是矩陣如果角度你不想使用季銨鹽）：

rotateCamera(oldDragPoint, newDragPoint) { 
    Quaternion quat = new Quaternion (Config.AngleX, Config.AngleY, Config.AngleZ); 
    quat.normalize(); 

    Quaternion deltaQuat = new Quaternion(); 
    deltaQuat = deltaQuat.setFromUnitVectors(oldDragPoint, newDragPoint); 

    quat = quat.multiply(deltaQuat); 
    quat.normalize(); 

    Vector3 resultAngles = Vector3(); 
    resultAngles.setFromQuaternion(quat); 

    setCameraPositionFromAngles(resultAngles); 
} 

而且在setCameraPositionFromAngles（resultAngles）通過將three basic rotations應用於初始相機位置來設置最終的X，Y，Z座標。所以你的主要參數是resultAngles。你更新角度，然後設置位置。

也許this working example會解釋得更好。