[Radiance-general] AGI 32 vs Radiance

[Shrikar Bhave]

Hi Kera and Rob,

Thanks a lot both for your input! I was only aware of the two items.
1. Radiosity vs. Raytracing
2. Limitations in modeling specular reflection

Good to know the details.

Shri



On Fri, Mar 13, 2015 at 11:41 AM, Guglielmetti, Robert <
Robert.Guglielmetti at nrel.gov> wrote:

> Wow Kera, all that info, and from your iPhone?! Impressive. Kera hit all
> the points, I think. I would only add that I think AGI *can* produce
> pretty convincing images, within the limitations of the radiosity approach
> (i.e. no true specular reflection model). In fact the brains behind AGI
> (Ian Ashdown) recently contributed to a thread on a LinkedIn forum about
> how AGI is the only commercial lighting simulation tool that can render
> chromatic adaptation (constancy), which is pretty damned impressive and
> goes along way toward "true to life" renderings.
>
> Shri, your specific case of wanting accuracy in the translucent realm is
> what finally drove me from Radiance dabbler to Radiance user many moons
> ago. Since then however, AGI has matured quite a bit. In my book, the
> inability to do climate based simulations and metrics is a non-starter,
> though.
>
>
> - Rob
>
>
> On 3/13/15, 9:19 AM, "Kera Lagios" <keralagios at gmail.com> wrote:
>
> >Hi Shri,
> >
> >Perhaps you know this already, but the major difference between AGI
> >and Radiance is that AGI uses radiosity rather than raytracing to
> >calculate light, and therefore does not calculate specularity or
> >specular light transmission. You can raytrace individual views in AGI,
> >but that applies Ray tracing to the direct component only and it does
> >not affect any calculated point grids. Qualitatively, visualizations
> >are less true to life. Ability to control your calculation parameters
> >in AGI is also limited.
> >
> >Another limitation with AGI is the ability to define complex
> >materials. In general the parameters are limited to tramsittance or
> >transparency and color. There is an option to add a texture, but I
> >think these are just image maps, although I would have to check. If
> >you are planning on using a complex definition for your materials, AGI
> >does not support that.
> >
> >Lastly, AGI doesn't support climate-based metrics/annual calculations or
> >DGP.
> >
> >I have heard that there are several papers and studies out there that
> >try to compare AGI, Radiance, and other softwares, but I don't have
> >any specific reference to give you.
> >
> >None of this is to say that AGI is not accurate, especially within
> >it's given capabilities, and in your case if the translucent material
> >you are using is 100% diffusing, and you do not need to address
> >specularity, daylight autonomy or DGP, you would likely get reasonable
> >results as far as the light transmission through the glazing. But in
> >the end, Radiance has much greater capacity to simulate daylight,
> >glare, materials, etc.
> >
> >I hope that helps,
> >Kera
> >
> >
> >Sent from my iPhone
> >
> >> On Mar 12, 2015, at 4:37 PM, Shrikar Bhave <shrikarbhave at gmail.com>
> >>wrote:
> >>
> >> Hello All,
> >> I have been put in an unusual situation of convincing someone that
> >>radiance is better and more scientifically accurate at simulating a
> >>daylighting scene which includes large application of translucent
> >>glazing. I haven't used AGI 32 at all to understand the nuances myself.
> >>
> >> Could someone please provide salient features comparing the two and/or
> >>point me to the correct resources? What I have found online hasn't been
> >>convincing. May be I am not searching in the right place.
> >>
> >> So that you know, the audience is not technically sound. But
> >>understands light well in the architectural context.
> >>
> >> Thanks in advance,
> >>
> >> Shri
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