POV-Ray : Newsgroups : povray.general : query - disappearing balls of fire Server Time
28 Mar 2024 13:49:48 EDT (-0400)
  query - disappearing balls of fire (Message 1 to 5 of 5)  
From: Bob Frew
Subject: query - disappearing balls of fire
Date: 13 May 2016 14:22:55
Message: <57361b7f$1@news.povray.org>
Hi all,
whilst changing an old scene to work under 3.7 I found a funny.
Have narrowed it down to the following.

using following code all is well and as expected, however if you change 
the position of the plane to +2 you lose the sphere ???
Am puzzled as to why.
Can use workaround of making image_map with negative plane and then 
rotate it 180*y

Is probably my understanding of things
			... Bob

plane {
   z, -2
   texture {
     pigment {
       image_map {
         png "test.png"
         interpolate 2 // smooth it
         once   // don't tile image, just one copy
       }
       // transform it to unit-size (-1 to +1)
       translate -0.5*(x+y) // center on the origin
       scale 2              // make it unit-sized
     }
     finish { ambient 0.3 }
   }
}

sphere { 0,1 pigment { rgbt 1 }  hollow                    // 
transparent sphere containing media
                              interior  { media { emission 20
                              density  { spherical density_map {
                                         [ 0 color rgbt <1, 0, 0,  1> ]
                                         [ 1 color rgbt <.9, 1, 0, -1> ] }
                          }   } } }


Post a reply to this message


Attachments:
Download 'p1_nbg.png' (5 KB) Download 'p1_ok.png' (6 KB)

Preview of image 'p1_nbg.png'
p1_nbg.png

Preview of image 'p1_ok.png'
p1_ok.png


 

From: Jaime Vives Piqueres
Subject: Re: query - disappearing balls of fire
Date: 13 May 2016 16:59:35
Message: <57364037$1@news.povray.org>
El 13/05/16 a las 20:22, Bob Frew escribió:
> Hi all, whilst changing an old scene to work under 3.7 I found a
> funny. Have narrowed it down to the following.
>
> using following code all is well and as expected, however if you
> change the position of the plane to +2 you lose the sphere ??? Am
> puzzled as to why.

   Because planes do have an interior too. You must make it hollow when
the media is inside (below) the plane.

--
jaime


Post a reply to this message

From: Bob Frew
Subject: Re: query - disappearing balls of fire
Date: 14 May 2016 07:15:20
Message: <573708c8$1@news.povray.org>
On 13/05/2016 21:59, Jaime Vives Piqueres wrote:
> El 13/05/16 a las 20:22, Bob Frew escribió:
>> Hi all, whilst changing an old scene to work under 3.7 I found a
>> funny. Have narrowed it down to the following.
>>
>> using following code all is well and as expected, however if you
>> change the position of the plane to +2 you lose the sphere ??? Am
>> puzzled as to why.
>
>   Because planes do have an interior too. You must make it hollow when
> the media is inside (below) the plane.
>
> --
> jaime
Hi Jaime,
many thanks for that.
I had always thought of a plane as like a piece of thin paper and the 
"inside/outside" as more of a consistency thing with other objects.

			... cheers Bob


Post a reply to this message

From: Alain
Subject: Re: query - disappearing balls of fire
Date: 14 May 2016 12:42:52
Message: <5737558c$1@news.povray.org>
Le 16-05-13 14:22, Bob Frew a écrit :
> Hi all,
> whilst changing an old scene to work under 3.7 I found a funny.
> Have narrowed it down to the following.
>
> using following code all is well and as expected, however if you change
> the position of the plane to +2 you lose the sphere ???
> Am puzzled as to why.
> Can use workaround of making image_map with negative plane and then
> rotate it 180*y
>
> Is probably my understanding of things
>              ... Bob
>

The plane have an interior. You must make it hollow or use the inverse 
option.

By the way, a disk object share the same interior as a coincident plane, 
and can affect nedias in the same way, outside of it's visible part.


Alain


Post a reply to this message

From: Warp
Subject: Re: query - disappearing balls of fire
Date: 23 May 2016 11:34:46
Message: <57432316@news.povray.org>
Bob Frew <bob### [at] ntlworldcom> wrote:
> I had always thought of a plane as like a piece of thin paper and the 
> "inside/outside" as more of a consistency thing with other objects.

A plane is a shape of infinite volume. One side is the inside, and
the other side is the outside.

If you eg. make a cube as an intersection of six planes (with their
normal vectors all pointing out of the cube), it will be a solid
shape, just like a box (in the sense that povray considers "solid";
ie. it can be used in CSG, and it won't contain media/fog by default).

-- 
                                                          - Warp


Post a reply to this message

Copyright 2003-2023 Persistence of Vision Raytracer Pty. Ltd.