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From: Mike Horvath
Subject: Cloth backdrop
Date: 4 Sep 2016 03:11:43
Message: <57cbc92f$1@news.povray.org>
Many times in photography you see smooth backdrops behind small objects 
so you don't see a sharp crease where a floor might meet a wall. How 
would I create one of these in POV-Ray? It would need to be circular 
since I might use any camera angle.

Thanks!


Mike


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From: Alain
Subject: Re: Cloth backdrop
Date: 4 Sep 2016 03:53:50
Message: <57cbd30e@news.povray.org>
Le 16-09-04 à 03:11, Mike Horvath a écrit :
> Many times in photography you see smooth backdrops behind small objects
> so you don't see a sharp crease where a floor might meet a wall. How
> would I create one of these in POV-Ray? It would need to be circular
> since I might use any camera angle.
>
> Thanks!
>
>
> Mike

Simple case:
The floor and wall are planes. You connect them using a clipped cylinder.

If the wall is curved, you replace the cylinder by a clipped torus.

In both cases, you can make the curvature of the link as small or large 
as you want.


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From: Mike Horvath
Subject: Re: Cloth backdrop
Date: 4 Sep 2016 08:24:38
Message: <57cc1286$1@news.povray.org>
On 9/4/2016 3:53 AM, Alain wrote:
> Le 16-09-04 à 03:11, Mike Horvath a écrit :
>> Many times in photography you see smooth backdrops behind small objects
>> so you don't see a sharp crease where a floor might meet a wall. How
>> would I create one of these in POV-Ray? It would need to be circular
>> since I might use any camera angle.
>>
>> Thanks!
>>
>>
>> Mike
>
> Simple case:
> The floor and wall are planes. You connect them using a clipped cylinder.
>
> If the wall is curved, you replace the cylinder by a clipped torus.
>
> In both cases, you can make the curvature of the link as small or large
> as you want.

Is there a smoother shape than a torus? I can still see a fuzzy seam.


Mike


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From: clipka
Subject: Re: Cloth backdrop
Date: 4 Sep 2016 08:49:20
Message: <57cc1850$1@news.povray.org>
Am 04.09.2016 um 09:11 schrieb Mike Horvath:
> Many times in photography you see smooth backdrops behind small objects
> so you don't see a sharp crease where a floor might meet a wall. How
> would I create one of these in POV-Ray? It would need to be circular
> since I might use any camera angle.

I'd probably use a cubic spline lathe; alternatively, a f(x)=pow(x,1/n)
surface of revolution might also work.

Cylinder&Torus-based solutions are probably prone to so-called mach
banding at the transition between the shapes (the illusion of brighter
or darker bands, related to the fact that the human eye is not only
sensitive to abrupt changes in brightness, but also to abrupt changes in
the the rate of change in brightness).


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From: Bald Eagle
Subject: Re: Cloth backdrop
Date: 4 Sep 2016 09:15:01
Message: <web.57cc1dc48f7556c45e7df57c0@news.povray.org>
What about:
(Hit [CTRL]-[F] and search for "tornado" )

http://bugman123.com/Renderings/index.html

?


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From: LanuHum
Subject: Re: Cloth backdrop
Date: 4 Sep 2016 16:05:00
Message: <web.57cc7dd68f7556c47a3e03fe0@news.povray.org>
Mike Horvath <mik### [at] gmailcom> wrote:
> Many times in photography you see smooth backdrops behind small objects
> so you don't see a sharp crease where a floor might meet a wall. How
> would I create one of these in POV-Ray? It would need to be circular
> since I might use any camera angle.
>
> Thanks!
>
>
> Mike

superellipsoid with cubic pattern: good room. Door and window:CSG


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From: Sherry K  Shaw
Subject: Re: Cloth backdrop
Date: 5 Sep 2016 11:18:38
Message: <57cd8cce$1@news.povray.org>
Mike Horvath wrote:
> Many times in photography you see smooth backdrops behind small objects
> so you don't see a sharp crease where a floor might meet a wall. How
> would I create one of these in POV-Ray? It would need to be circular
> since I might use any camera angle.
>
> Thanks!
>
>
> Mike

Perhaps a mesh...?  Estimate the sort of curve you need and use nested 
loops to generate an array of points.  It has the advantage of being 
fairly easy to tweak.

--Sherry K. Shaw

-- 
#macro T(E,N)sphere{x,.4rotate z*E*60translate y*N pigment{wrinkles scale
.3}finish{ambient 1}}#end#local I=0;#while(I<5)T(I,1)T(1-I,-1)#local I=I+
1;#end camera{location-5*z}plane{z,37 pigment{granite color_map{[.7rgb 0]
[1rgb 1]}}finish{ambient 2}}//                                   TenMoons


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From: Mike Horvath
Subject: Re: Cloth backdrop
Date: 5 Sep 2016 17:23:35
Message: <57cde257$1@news.povray.org>
On 9/5/2016 11:18 AM, Sherry K. Shaw wrote:
> Mike Horvath wrote:
>> Many times in photography you see smooth backdrops behind small objects
>> so you don't see a sharp crease where a floor might meet a wall. How
>> would I create one of these in POV-Ray? It would need to be circular
>> since I might use any camera angle.
>>
>> Thanks!
>>
>>
>> Mike
>
> Perhaps a mesh...?  Estimate the sort of curve you need and use nested
> loops to generate an array of points.  It has the advantage of being
> fairly easy to tweak.
>
> --Sherry K. Shaw
>

I think the only way to get rid of the seam completely is to create a 
giant sphere with the light source in the middle, then put the scene 
objects on the bottom inner surface of the sphere. But that will create 
weird shadows and a lot of objects getting clipped by the sphere.

Mike


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From: Mike Horvath
Subject: Re: Cloth backdrop
Date: 5 Sep 2016 17:25:15
Message: <57cde2bb$1@news.povray.org>
On 9/4/2016 9:12 AM, Bald Eagle wrote:
> What about:
> (Hit [CTRL]-[F] and search for "tornado" )
>
> http://bugman123.com/Renderings/index.html
>
> ?
>
>
What?


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From: StephenS
Subject: Re: Cloth backdrop
Date: 5 Sep 2016 18:51:07
Message: <57cdf6db$1@news.povray.org>
On 04/09/2016 3:11 AM, Mike Horvath wrote:
> Many times in photography you see smooth backdrops behind small objects
> so you don't see a sharp crease where a floor might meet a wall. How
> would I create one of these in POV-Ray? It would need to be circular
> since I might use any camera angle.
>
> Thanks!
>
>
> Mike
Try:
prism{
  bezier_spline
  ...
}
to simulate one side of a cloth hanging from cieling and draped on floor.

or

lathe{
  bezier_spline
  ...
}

With the bezier_spline you can have true flat surface to place objects 
and curve without seam.

Stephen S


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