dipityPix app

Wednesday, July 29, 2015

Testing near Brewster's angle

Yesterday's picture had specular reflections that were way off.  I tried a bunch of tests on my Fresnel equations and they seemed ok.   I tried Brewster's Angle for the glass and this found one big problem: my model!   Note that with LCD screens, no polarizers are needed to see Brewster's angle in action!  Here's two photographs of the iPad at Brewster's Angle:

The ipad produces almost perfectly polarized light, and at Brewster's Angle only one of the polarizations is reflected.   By rotating the iPad you can change the polarization of the incident light 90 degrees.
It occurred to me that maybe I just had the polarization 90 degrees wrong in my input model.   That definitely is one of my problems!   So more complete testing tomorrow.
Rendered images.   Left: my incorrect input with polarization exactly wrong.   Right: fixed model.   Not exactly at Brewster's angle so some reflection is visible.

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