RE: [Algorithms] Solid angle calculation

[Peter-Pike S. <pp...@mi...>]

I believe this is just the differential solid angle for the sphere map
parameterization.  Using sin(theta) would only be correct for a lat/long
parameterization...

-Peter-Pike

(I don't think this has anything to do with low pass filters...)

-----Original Message-----
From: Ber...@ma... [mailto:Ber...@ma...]=20
Sent: Wednesday, September 18, 2002 4:48 AM
To: gda...@li...
Subject: RE: [Algorithms] Solid angle calculation



> > > domega =3D (2*PI/width)*(2*PI/width)*sinc(theta) ;
> > >=20
> > > I understand where the / width comes from since you are
> > integrating in
> > > steps of 1/width over the sphere, but I fail to understand what
> > > sinc(theta) means.

> We know what sinc _is_ - Joris even gave the code for it. The
> question is
> why is it being used here?

On a hunch : because they are using proper monte carlo integration
around (rather than just taking a single point=20
sample at) the angle of interest, during which they
use the sync as a lowpass filter to remove frequencies=20
beyond the nyquist limit ?

So that would basically be a misleading name -- it's not
just the differential angle required by the numerical integration, it's
also carrying the value of the filter being convolved with.

I would expect to see a double loop, whereas the net
samples you mention that don't use sinc, only have
one loop.

Or maybe not :)

Bert


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