How does view direction node work?

Unity Engine
1

I’m following this youtube tutorial:

Why is it that view direction minus position gives you the result seen in the preview?
Isn’t view direction calculated as position from the camera minus vertex position?
But if that was the case, substracting the position to the view direction would give back the camera position.

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Thanks!

2

Probably the subtraction is made as the further the vertex is from the center of the object, the larger the result returned with the distance node. And the view direction is used to relate the process to the camera. I suppose it is a fresnel approximation.