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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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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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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What about:
(Hit [CTRL]-[F] and search for "tornado" )

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

?

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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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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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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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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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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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> 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.

A sphere is the simple option, as it has a constant radius of curvature 
everywhere. There are other shapes though - the curves used on modern 
car body panels are very good examples of complex shapes with no visible 
seams.

clipka mentioned it already, you need a shape that not only has no 
abrupt changes in surface normal direction (eg using a cylinder to join 
two planes), but also no abrupt changes in the rate of change of surface 
normal. This is especially true if your shape is in anyway reflective 
(including specular highlights). You may even want to make sure the 2nd 
or 3rd derivative of surface normal direction has no jumps in it to 
ensure you are completely seam-free.

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