RE: [Algorithms] Solid angle calculation

[Tom F. <to...@mu...>]

I assumed that was a typo, and they mean "sine(theta)". But I didn't worry
about it too hard since, using cube-maps and just ignoring the spherical
distortion (i.e. every sample is evenly weighted) seemed to work just fine -
at least to within the tolerance of my eye :-). It also bins all the angle
stuff and uses the SH components directly (since you already have x,y,z to
plug into the component calculations), so there's no trig anywhere in any
equations. Which is very good news for speed.


Tom Forsyth - purely hypothetical Muckyfoot bloke.

This email is the product of your deranged imagination,
and does not in any way imply existence of the author.

> -----Original Message-----
> From: Joris Mans [mailto:jor...@pa...]
> Sent: 12 September 2002 02:17
> To: gda...@li...
> Subject: [Algorithms] Solid angle calculation
> 
> 
> Hi
> 
> I am currently trying to understand/implement the integration scheme
> used in "An efficient rep. for Irradiance env maps" and I 
> think my math
> skills have some holes in them, because I don't understand the formula
> for calculating the solid angle.
> This is the c sample code:
> 
> domega = (2*PI/width)*(2*PI/width)*sinc(theta) ;
> 
> 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. 
> 
> FYI:
> 
> float sinc(float x) {               /* Supporting sinc function */
>   if (fabs(x) < 1.0e-4) return 1.0 ;
>   else return(sin(x)/x) ;
> }
> 
> How does this term calculate the solid angle?
> 
> Thanks
> 
> Joris
> 
> 
> 
> -------------------------------------------------------
> In remembrance
> www.osdn.com/911/
> _______________________________________________
> GDAlgorithms-list mailing list
> GDA...@li...
> https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list
> Archives:
> http://sourceforge.net/mailarchive/forum.php?forum_id=6188
>