[Radiance-general] ambient occlusion map ?

[Mark Stock]

That was my first suspicion as well, but the halo remained even after 
dropping specularity to zero.

Computers have been doing extremely weird stuff for me these last few 
days. Is there a big solar flare or something?

Mark

On Fri, 15 Mar 2013, Greg Ward wrote:

> Hi Mark,
>
> I suspect you are seeing specular samples from low angles on your black 
> frame.  If the frame has a roughness below 0.001 or so and non-zero 
> specularity, the Fresnel coefficient will cause the specularity to go to 
> nearly 1 as you approach grazing.  This is correct behavior, but in 
> regions near the inside edge, this will cause stray, bright sample 
> values in your ambient calculation.  The only way to fix it is to set 
> roughness above 0.002 or set specularity to zero on your surface.
>
> I haven't downloaded your model to confirm the material parameters, so 
> I'm really just guessing.
>
> Cheers,
> -Greg
>
> Sent from my iPad
>
> On Mar 15, 2013, at 9:53 AM, Andrew McNeil <amcneil at lbl.gov> wrote:
>
>> Brajesh,
>>
>> This is expected behavior.  As Chris pointed out glow sources are sampled using the ambient calculation.  This is because glow was intended to model the sky, a very large area source.  It is much more efficient and accurate to sample the sky using the stochastic ambient calculation compared of the deterministic direct calculation.
>>
>> With -ab 0 you get no light in your image from the glow (unless you can see the glow geometry in your view).  Setting -ab 1 when using a glow source is equivalent to a direct only calculation (ie without any inter-eflection effects).
>>
>> Andy
>>
>>
>> On Fri, Mar 15, 2013 at 9:39 AM, Brajesh Lal <brajeshlal at yahoo.com> wrote:
>>>
>>> I render the image from camera point of view as i captured the real world scene.
>>> and if i put any distant liht source e.g. sun -   then i can see the scene. but  can see the scene if we use object as light source...
>>>
>>>
>>> Best Regards, Brajesh Lal
>>> From: Christopher Rush <Christopher.Rush at arup.com>
>>> To: Radiance general discussion <radiance-general at radiance-online.org>
>>> Sent: Friday, March 15, 2013 4:57 PM
>>> Subject: Re: [Radiance-general] ambient occlusion map ?
>>>
>>> Are you tracing the pixels from a view point looking at the black surface, to show the irradiance caused by the glow source, which is behind your view point contributing onto the black mesh surface? And the view point is a parallel projection?
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