[Radiance-general] Shadow above highlight?

[Andrew McNeil]

I agree with John that the root cause of the shadow is the sampling behavior
of Radiance.  With only one ambient bounce the black hole in the window, and
the walls in general shouldn't affect the luminance of the ceiling.

If there were more than one bounce, than the black hole would be a factor,
but it would probably be much less defined as all surfaces in the room see
the hole. 

One way to test is to fill in the hole and create a polygon with glow
material to replace the sun patch on the floor.

Andy



On 8/17/09 10:52 AM, "schwaj3 at rpi.edu" <schwaj3 at rpi.edu> wrote:

> I might agree with you, but I think if it was the window, then not only
> the ceiling, but also the right and left walls would probably have dark
> spots on them as well (maybe also the backwall?). It should be noted that
> the dark spot is always directly above the highlight on the floor as the
> time of day changes. I don't really understand what you mean by coupling,
> but I don't believe that the shadow is related to the window, rather it
> is related to the highlight on the floor. If I change the shape of the
> aperture to an asymmetrical shape, such as a square with a triangle on
> top, then the shadow on the ceiling seems to be a mirror image of the
> highlight on the floor, rather than a projection of the window. Note that
> the two would have the triangle shape on opposite sides of the ceiling
> shadow. I'm not sure if that helps answer your question.
> 
> The radiosity program I am using does not create a shadow in that
> location, (or on other walls either). I believe if anything, radiosity
> might simply be darker/lighter in general.
> 
> --John
> 
> ==============Original message text===============
> On Mon, 17 Aug 2009 13:24:46 EDT "Zack Rogers" wrote:
> 
> Hi John,
> 
> Even without this funny sampling behavior I think there could be a
> slightly darker patch on the ceiling due to the 1/3 x 1/3 square on the
> adjacent wall that has a 0% reflectance.  That dark portion of the
> ceiling could just have a stronger coupling to the 0% reflectance surface
> than the other surfaces around.  Do your radiosity renderings show any
> darker spots on the ceiling?
> 
> Cheers,
> Zack
> 
> 
> ________________________________
> 
>   ZACK ROGERS, P.E., LEED AP, IESNA
>  
> INTEGRATED DESIGN ASSOCIATES, INC
> 437 Main Street
> Longmont, CO 80501
> tel: 303.848.8299, fax: 303.848.8290
> www.ideasi.com 
> 
> -----Original Message-----
> From: radiance-general-bounces at radiance-online.org
> [mailto:radiance-general-bounces at radiance-online.org] On Behalf Of Thomas
> Bleicher
> Sent: Friday, August 14, 2009 2:58 AM
> To: Radiance general discussion
> Subject: Re: [Radiance-general] Shadow above highlight?
> 
> On Fri, Aug 14, 2009 at 12:44 AM, Greg Ward <gregoryjward at gmail.com> wrote:
>> 
>> Hi John,
>> 
>> I spent a little time looking at your model, and there are some
> irregularities that I'm not sure are intentional.  Specifically, I
> rendered a view from the darker region of the ceiling looking down like so:
> 
> [...]
> 
>> The light patch is the one seen at the bottom of your original view,
> but the dark patch below it (actually towards the camera in your first
> view) is peculiar.  It appears to be an opening, where light goes but
> does not return.  Was this what you meant to do?  Are you radiosity
> calculations OK with this?  Infinite rays may cause some oddities in the
> interpolation, which I think is at least part of what we are seeing in
> the 10-20% level drop in the dark patch on the ceiling.
> 
> 
> The dark patch should be the window opening. The ground glow has been
> removed from the sky description so you look into the ...
> 
> ... cold dark void. [cue flash and rolling thunder]
> 
> Thomas ;)
> 
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