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Lecture 14: Material Modeling (3)

The idea behind how bike reflectors work: the outside surface is smooth to allow light to enter while the inside surface is an array of spherical beads or prisms. The light striking the inside surface undergoes total internal reflection. Due to the orientation of the other inside surfaces, any light internally reflecting is directed back out the front of the reflector in the direction it came from. See the visual here.


Another interesting type of reflection is the mixed (specular+diffuse) reflection. Read more about it here:


I understand the general idea behind this slide but want some more intuition on what the shapes in this slide represent. Do they correspond to a probabilistic model of the reflection direction of an incoming light ray? If the incoming ray carries a light intensity of quantity x, does the shape dictate how that x quantity of light is reflected out (so in the case of ideal diffuse, each direction would get a light ray of x / Area_hemisphere intensity)?


It would be interesting to play around with the reflection function shapes for various different textures, to see the effect it gives on the texture. I'd be interested in what a "radially striped" pinwheel-type reflection fn would give. How would we create the effect of a rough course sand-papery texture via an approach like this? (As in, would it be possible to give the appearance of texture coarseness solely by using a particular reflection function, instead of other approaches we've covered in this class)?


In lecture it was mentioned that the moon has a bit of the characteristic of a retroreflector surface, but a really cool use of retroreflector surfaces is Apollo missions leaving retroflectors on the moon and aiming lasers from observatories at them to get a roundtrip duration that can be used to measure the distance between the Earth and the Moon.

Can read more about it here


Hersh, it's interesting that you bring up the reflection function for sandpaper; sandpaper was investigated for use as a Lambertian standard reference reflector for the IR spectrum back in the 80s! Check it out here:

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