Re: [Algorithms] Undershooting in spherical harmonics generated by cubemap convolution

[Fabian G. <f.g...@49...>]

Hi Alen,

> So to ask a concrete question: Is it normal for SH approximation
> errors in such "spiky" cases to generate undershooting in directions
> that are not directly opposite to the brightest point?

If you look at the basis functions for l=2:

   http://web.uniovi.es/qcg/harmonics/harmonics.html

you should see what's going on. For first order SH, you will indeed only 
get undershooting in the opposite direction, since all the functions are 
point-symmetric around zero. The second order SH basis functions aren't 
(and their symmetries are rotations by multiplies of 90 degrees, not 
180, around the Z axis), so you'll get undershooting in other places too.

Kind regards,
-Fabian Giesen