RE: [Algorithms] Intensity gamma correction of spherical harmonics
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RE: [Algorithms] Intensity gamma correction of spherical harmonics
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From: Peter-Pike S. <pp...@wi...> - 2006-02-27 17:33:26
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That won't actually work. Gamma is a non-linear function, so you have to do something else (same goes for any non-linear function...) The easiest thing to do is to blow things out to the spatial domain, do the operation, and project back to SH. =20 Things like products are different (and are just linear - either via the generic triple product tensor or the "signal specialized" product matrix.) -Peter-Pike -----Original Message----- From: gda...@li... [mailto:gda...@li...] On Behalf Of Jarkko Lempiainen Sent: Monday, February 27, 2006 8:17 AM To: gda...@li... Subject: RE: [Algorithms] Intensity gamma correction of spherical harmonics I don't think raising each SH coeff to power works - atleast the way you expect. For raising spherical function to power in spatial domain you essentially want to apply "shadow function" over another function as descriped in "Spherical Harmonic Lighting: The Gritty Details", Page 19, Equations 8 & 9. In your case the shadow function b(s) is the function itself (in case of power of 2), but I don't think that the sum over j of M_ij becomes a_i, though there's high propability I'm wrong since I didn't verify it ;) Anyway, using that shadow function equation it should be relatively easy to derive the correct equation for the power operation, if that's the operation you want in the first place. Jarkko -----Original Message----- From: gda...@li... [mailto:gda...@li...] On Behalf Of Pau...@sc... Sent: February 27, 2006 4:55 AM To: gda...@li... Subject: Re: [Algorithms] Intensity gamma correction of spherical harmonics gda...@li... wrote on 26/02/2006 16:23:01: > Our engine uses spherical harmonics to encode incoming lighting information. >=20 > Is there a way to make dark areas of the SH sphere darker and bright areas > brighter > without converting harmonics to image space and applying color correction > and than coverting it back to harmonics ? What about just raising each coefficient to a power? A bit arbitrary, but might work ok... Cheers, Paul. ********************************************************************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify pos...@sc... This footnote also confirms that this email message has been checked for all known viruses. ********************************************************************** Sony Computer Entertainment Europe ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=3Dlnk&kid=3D110944&bid=3D241720&dat=3D= 121642 _______________________________________________ GDAlgorithms-list mailing list GDA...@li... https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list Archives: http://sourceforge.net/mailarchive/forum.php?forum_id=3D6188 ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=3Dk&kid=110944&bid$1720&dat=121642 _______________________________________________ GDAlgorithms-list mailing list GDA...@li... https://lists.sourceforge.net/lists/listinfo/gdalgorithms-list Archives: http://sourceforge.net/mailarchive/forum.php?forum_ida88 |