I was trying to figure out how to do some things with the mouse, and what better way then trying stuff out so I did this on a local script
Mouse=game.Players.LocalPlayer:GetMouse()
print(Mouse.hit)
the output printed as
0, 0, 0, NAN, NAN, NAN, NAN, NAN, NAN, NAN, NAN, NAN
NAN is short for "Not A Number". C (ROBLOX stuff) calls it this -- Lua calls it something like "#INDEF" (indefinite).
Operations like 0/0 will cause this to appear.
Any operation on NaN will produce another NaN.
NaNs are usually big problems because of this, since they will "contaminate" any other values you try to use them with. Since only a few operations can create them (inverse trig functions and division by zero and operations on infinity), you only need to be careful of a few cases (usually just division).
In this case particular case of the Hit property, it isn't your math; ROBLOX has decided these values behind-the-scenes.
It probably means that the camera is not defined correctly or the mouse hasn't "loaded" yet (the player hasn't pointed at anything or is not pointed at anything).
Regardless, those NaNs are okay, though, because the orientation of the Hit property isn't ever important, only the position .p is, which is the first three numbers - and those are not NaN.
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