[Bf-cycles] GSoC - Spectral Rendering

Agustin Benavidez agustinbenavidez at gmail.com
Wed Apr 10 03:36:03 CEST 2013

Hi, my humble opinion is that this idea somehow doesn't fit into the Cycles
philosophy and focus which is be the best balance between speed and
realism/accuracy and animation oriented, We already got great render
engines capable of that integrated in blender like Luxrender, spending a
Summer Of Code slot to re-do what others complementary OOS projects do best
is not worth.

Here is what you can already do with a relative simple node setup:


I understand dispersion is not only about little rainbows, but I agree with
Dalai, and don't see this improving Cycles general usage.
Anyway We need to be open and will be nice to see some examples of the
quality boost that this could bring :)
Best regards.

2013/4/9 Gavin Howard <gavin.d.howard at gmail.com>

>      David,
>      Cycles has a subsurface scatter node in the development builds,
> correct? If that's the case, I will see if I can render some scenes in
> Cycles and LuxRender to show the difference. It's not going to be the
> best, but it should show something.
>      Gavin H.
> On Tue, Apr 9, 2013 at 5:20 PM, David <erwin94 at gmx.net> wrote:
> > On Apr 10, 2013, at 12:55 AM, Brecht Van Lommel wrote:
> >> On Wed, Apr 10, 2013 at 12:08 AM, David <erwin94 at gmx.net> wrote:
> >>> this is by far the best visual explanation of what separates spectral
> >>> rendering from normal RGB rendering that I have seen:
> >>>
> >>>
> http://www.luxrender.net/wiki/LuxRender_Textures_Spectrum#Gaussian_spectrum
> >>>
> >>> All lamps in this image would be the same RGB color, and produce the
> >>> same result with non-spectral rendering.
> >>
> >> I don't think that's true? The exact result depends on the wavelength
> >> to RGB conversion function, but a wider gaussian distribution across
> >> the wavelength should give different RGB values than a narrow one? As
> >> the distribution gets wider there will a more even distribution across
> >> the RGB channels.
> >>
> >> It wouldn't be as accurate but the lights would still render different
> I think?
> >>
> >> Brecht.
> >
> > Ah, you're right, and it is even sort of explained in the text I linked
> to, so I
> > feel especially dumb. ;)  The width of the distribution corresponds
> roughly to
> > saturation, it's basically just HSV.
> > So, the only effect that I can think of that is really not approximated
> by RGB
> > rendering is dispersion? I would love to see an image where the light
> spectrum
> > makes a noticeable difference, that isn't of a prism or a diamond...
> >
> > till then, David.
> >
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