Why is the scale of this MouseY set to -1?


First person shooter programming - to achieve mouse camera control, why is this MouseY’s scale set to -1?
I used the blueprint for the output, the mouse forward, the value of axis value is positive.Multiplied by -1 into negative.pitch is negative.Why not toward the bottom?

It’s just a convention. I suppose it comes from the fact that the top left of the screen is designated as (0,0) and the bottom right is (ResX,ResY). I suppose it started a very long time ago (2D), where moving the mouse forwards meant you’re moving the cursor upwards (decreasing the Y value).

Thank you very much, but I don’t know whether it is correct.

I see the code, whether it is because it multiply by scale again.