I wrote a mouse look feature that works similarly to most spectator camera systems. Every frame the mouse cursor is locked to the center of the viewport.
Whenever the mouse moves, I want to know the difference vector so I can determine how to orient the camera. I found myself having to use offsets such as -4 for the x value and -30 for the y value in order to get it to work. I am using the ScreenToClient Function so I would think that offsets wouldn't be needed. Furthermore, while my -30 offset works for all the windows platforms I have run my demo on, my X offset seems to need to be changed from platform to platform. For example, on Windows 7, the -4 offset works fine however on XP it causes the camera to be continually rotated. However on XP, a value of -8 works while on Windows 7 I get the same issue. I assume this is due to that fact that each OS has different sized menu bars which contribute to the overall position of the mouse however as I stated, I am using the ScreenToClient function which I thought was suppose to handle this issue. Any additional information would be highly appreciated!




if(GetAsyncKeyState(VK_RBUTTON) & 0x8000)
{
GetCursorPos(&m_pntCurrentCursorPosition);
ScreenToClient(m_hWnd, &m_pntCurrentCursorPosition);

double fXDiff = m_pntCurrentCursorPosition.x - ((iScreenWidth/2)-4); // On Windows 7, 4 should be 8 but on Windows XP, it should be 4.
double fYDiff = m_pntCurrentCursorPosition.y - ((iScreenHeight/2)-30);
...
}


Where do you get iScreenWidth and iScreenHeight? From the client rect? If you get them from the window rect, that's where the extra offsets come from.

Hmm... ok so I modified the code to look like this but still to no avail...



if(GetAsyncKeyState(VK_RBUTTON) & 0x8000)
{
RECT rectWindow;
RECT rectScreen;
GetCursorPos(&m_pntCurrentCursorPosition);
ScreenToClient(m_hWnd, &m_pntCurrentCursorPosition);
GetWindowRect(m_hWnd, &rectWindow);
GetClientRect(m_hWnd, &rectScreen);

double dXOffset = rectWindow.right - rectScreen.right;
double dYOffset = rectWindow.bottom - rectScreen.bottom;

double fXDiff = m_pntCurrentCursorPosition.x - ((rectScreen.right/2) - dXOffset);
double fYDiff = m_pntCurrentCursorPosition.y - ((rectScreen.bottom/2) - dYOffset);
...
// Lock the cursor back in place.
SetCursorPos((rectScreen.right/2), (rectScreen.bottom/2));
}


Thanks but the camera is still rotating with your proposed changes.

Ah I fixed it! Stupid error... I forgot to take out the


ScreenToClient(m_hWnd, &m_pntCurrentCursorPosition);


Everything works now. Thanks!