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This tutorial about radiosity:
http://wiki.povray.org/content/HowTo:Use_radiosity#Step_5:_Find_Your_Error_Bound
says:
> Sometimes radiosity can cause artifacts, one of the most common
causes of artifacts is infinite radiosity rays. A good rule is to place
any radiosity scene inside a large inverse sphere to avoid any ray
colliding with the background or sky_sphere.
What is an inverse sphere? And how is it useful/beneficial in this
situation? Thanks.
Michael
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On 5/28/2019 2:52 PM, Mike Horvath wrote:
> This tutorial about radiosity:
>
> http://wiki.povray.org/content/HowTo:Use_radiosity#Step_5:_Find_Your_Error_Bound
>
>
> says:
>
> > Sometimes radiosity can cause artifacts, one of the most common
> causes of artifacts is infinite radiosity rays. A good rule is to place
> any radiosity scene inside a large inverse sphere to avoid any ray
> colliding with the background or sky_sphere.
>
> What is an inverse sphere? And how is it useful/beneficial in this
> situation? Thanks.
>
>
> Michael
Oops! That link should be:
http://wiki.povray.org/content/HowTo:Use_radiosity#Artifacts
Michael
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Mike Horvath <mik### [at] gmail com> wrote:
> What is an inverse sphere?
It's a spherical cavity inside the [solid] infinite POV-Ray space.
A solid sphere's inverse.
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Le 28/05/2019 à 22:45, Bald Eagle a écrit :
>
> Mike Horvath <mik### [at] gmailcom> wrote:
>
>> What is an inverse sphere?
>
> It's a spherical cavity inside the [solid] infinite POV-Ray space.
>
> A solid sphere's inverse.
>
and for the code oriented, it looks like:
sphere { 0, 1e+5 inverse ...
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On 29-5-2019 7:48, Le_Forgeron wrote:
> Le 28/05/2019 à 22:45, Bald Eagle a écrit :
>>
>> Mike Horvath <mik### [at] gmailcom> wrote:
>>
>>> What is an inverse sphere?
>>
>> It's a spherical cavity inside the [solid] infinite POV-Ray space.
>>
>> A solid sphere's inverse.
>>
>
> and for the code oriented, it looks like:
>
> sphere { 0, 1e+5 inverse ...
>
alternatively, although less elegant: sphere {0, 1e+5 hollow ...} gives
the same result.
--
Thomas
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Le 19-05-28 à 14:52, Mike Horvath a écrit :
> This tutorial about radiosity:
>
> http://wiki.povray.org/content/HowTo:Use_radiosity#Step_5:_Find_Your_Error_Bound
>
>
> says:
>
> > Sometimes radiosity can cause artifacts, one of the most common
> causes of artifacts is infinite radiosity rays. A good rule is to place
> any radiosity scene inside a large inverse sphere to avoid any ray
> colliding with the background or sky_sphere.
>
> What is an inverse sphere? And how is it useful/beneficial in this
> situation? Thanks.
>
>
> Michael
It can be a sphere with the «inverse» attribute, or a sphere with the
hollow attribute.
The use of inverse or hollow is to allow the use of fog and media.
In my experience, I have never encountered any case where infinite rays
have caused any artifacts.
My guess is it's a leftover from the early radiosity implementation that
still had a max_distance setting that imposed a cutoff distance when
testing for radiosity samples.
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