You are viewing the course site for a past offering of this course. The current offering may be found here.
Lecture 14: Material Modeling (16)

Is there a reason why w_i is pointed outwards away from the surface as opposed to pointed towards the surface — is it just so that the equation is easier to understand/comprehend? I thought w_i, being the incoming ray, should be pointed towards the incident surface


wiw_i and wow_o are simply the two distinct equal-length outward-pointing vectors along the path of a reflected light. The point of the left diagram is to show that a perfect reflection will satisfy wo=wi+2(win)nw_o = -w_i + 2(w_i \cdot \vec{n})\vec{n}. I can see why this could be confusion since lights would travel in the direction of wiw_i and wo-w_o (or wi-w_i and wow_o).


To emilyzhong, fywu85: I believe wiw_i points outwards away from the surface so that cosθcos \theta is equal to the dot product between wiw_i and n\vec{n}. If it pointed towards the surface, then we can get the same result by replacing wiw_i with wi-w_i.

You must be enrolled in the course to comment