我使一个物体在相机前面移动。我将旋转矩阵乘以对象矩阵，以使对象重复进行摄影机转换。问题在于，倾斜摄像机时，物体也会倾斜。倾斜相机时，物体不应相对于屏幕旋转。怎么办？
此代码段。
void UpdateCamera()
{
// Rotate target around camera
camRotationMatrix = XMMatrixRotationRollPitchYaw(camPitch, camYaw, 0);
camTarget = XMVector3TransformCoord(DefaultForward, camRotationMatrix );
camTarget = XMVector3Normalize(camTarget);
XMMATRIX RotateYTempMatrix;
RotateYTempMatrix = XMMatrixRotationY(camYaw);
// Walk
camRight = XMVector3TransformCoord(DefaultRight, RotateYTempMatrix);
camForward = XMVector3TransformCoord(DefaultForward, RotateYTempMatrix);
camUp = XMVector3Cross(camForward, camRight);
// Free Cam
camRight = XMVector3TransformCoord(DefaultRight, camRotationMatrix);
camForward = XMVector3TransformCoord(DefaultForward, camRotationMatrix);
camUp = XMVector3Cross(camForward, camRight);
camPosition += moveLeftRight*camRight;
camPosition += moveBackForward*camForward;
moveLeftRight = 0.0f;
moveBackForward = 0.0f;
camTarget = camPosition + camTarget;
// Third Person Camera
// Set the cameras target to be looking at the character.
camTarget = charPosition;
camTarget = XMVectorSetY(camTarget, XMVectorGetY(camTarget)+5.0f);
// Rotate camera around target
camRotationMatrix = XMMatrixRotationRollPitchYaw(-camPitch, camYaw, 0);
camPosition = XMVector3TransformNormal(DefaultForward, camRotationMatrix );
camPosition = XMVector3Normalize(camPosition);
// Set our cameras position to rotate around the character.
// to be "standing" on (0,0,0), instead of centered around it ;) Well target her head here though
camPosition = (camPosition * charCamDist) + camTarget;
camForward = XMVector3Normalize(camTarget - camPosition); // Get forward vector based on target
camForward = XMVectorSetY(camForward, 0.0f); // set forwards y component to 0 so it lays only on
// the xz plane
camForward = XMVector3Normalize(camForward);
// To get our camera's Right vector, we set it's x component to the negative z component from the
// camera's forward vector, and the z component to the camera forwards x component
camRight = XMVectorSet(-XMVectorGetZ(camForward), 0.0f, XMVectorGetX(camForward), 0.0f);
// Our camera does not "roll", so we can safely assume that the cameras right vector is always
// in the xz plane, so to get the up vector, we just get the normalized vector from the camera
// position to the cameras target, and cross it with the camera's Right vector
camUp =XMVector3Normalize(XMVector3Cross(XMVector3Normalize(camPosition - camTarget), camRight));
camView = XMMatrixLookAtLH( camPosition, camTarget, camUp );
}
void DetectInput(double time)
{
DIMOUSESTATE mouseCurrState;
BYTE keyboardState[256];
DIKeyboard->Acquire();
DIMouse->Acquire();
DIMouse->GetDeviceState(sizeof(DIMOUSESTATE), &mouseCurrState);
DIKeyboard->GetDeviceState(sizeof(keyboardState),(LPVOID)&keyboardState);
if(keyboardState[DIK_ESCAPE] & 0x80)
PostMessage(hwnd, WM_DESTROY, 0, 0);
float speed = 10.0f * time;
bool moveChar = false;
XMVECTOR desiredCharDir = XMVectorSet(0.0f, 0.0f, 0.0f, 0.0f);
if(keyboardState[DIK_A] & 0x80)
{
desiredCharDir += (camRight);
moveChar = true;
}
if(keyboardState[DIK_D] & 0x80)
{
desiredCharDir += -(camRight);
moveChar = true;
}
if(keyboardState[DIK_W] & 0x80)
{
desiredCharDir += (camForward);
moveChar = true;
}
if(keyboardState[DIK_S] & 0x80)
{
desiredCharDir += -(camForward);
moveChar = true;
}
if((mouseCurrState.lX != mouseLastState.lX) || (mouseCurrState.lY != mouseLastState.lY))
{
camYaw += mouseLastState.lX * 0.002f;
camPitch += mouseCurrState.lY * 0.002f;
// Normalize our destinated direction vector
desiredCharDir = XMVector3Normalize(desiredCharDir);
if (XMVectorGetX(XMVector3Dot(desiredCharDir, oldCharDirection)) == -1)
oldCharDirection += XMVectorSet(0.02f, 0.0f, -0.02f, 0.0f);
// Get our current characters position in the world, from it's world matrix
charPosition = XMVectorSet(0.0f, 0.0f, 0.0f, 0.0f);
charPosition = XMVector3TransformCoord(charPosition, playerCharWorld);
// Rotate our character smoothly when changing direction (from the GPG series)
float destDirLength = 10.0f * frameTime; // Change to the speed you want your character to rotate. This uses the game timer from an earlier lesson
// The larget this value, the faster the character rotates
currCharDirection = (oldCharDirection)+(desiredCharDir * destDirLength); // Get the characters direction (based off time, old position, and desired
// direction), by adding together the current direction and the old direction
// to get vector that smoothly turns from oldCharDir to denstinationDirection
currCharDirection = XMVector3Normalize(currCharDirection); // Normalize the characters current direction vector
// the opposite of what it currently is, giving us the result in -1 PI to 1 PI.
float charDirAngle = XMVectorGetX(XMVector3AngleBetweenNormals(XMVector3Normalize(currCharDirection), XMVector3Normalize(DefaultForward)));
if (XMVectorGetY(XMVector3Cross(currCharDirection, DefaultForward)) > 0.0f)
charDirAngle = -charDirAngle;
// Now we update our characters position based off the frame time, his old position, and the direction he is facing
float speed = 15.0f * frameTime;
charPosition = charPosition + (desiredCharDir * speed);
// Update characters world matrix
Scale = XMMatrixScaling(0.25f, 0.25f, 0.25f);
Translation = XMMatrixTranslation(XMVectorGetX(charPosition), 0.0f, XMVectorGetZ(charPosition));
playerCharWorld = Scale * XMMatrixRotationRollPitchYaw(-camPitch, camYaw, 0) * Translation;
// Check that the camera doesn't go over the top or under the player
if(camPitch > 0.85f)
camPitch = 0.85f;
if(camPitch < -0.85f)
camPitch = -0.85f;
mouseLastState = mouseCurrState;
}
我设置了角色世界矩阵
playerCharWorld = Scale * XMMatrixRotationRollPitchYaw(-camPitch, camYaw, 0) * Translation;
为使角色重复相机的旋转，我乘以XMMatrixRotationRollPitchYaw（-camPitch，camYaw，0）倾斜相机时，角色也会倾斜。倾斜相机时如何使角色不倾斜？