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25 Dec 2024 01:55:32 EST (-0500)
  Wallpaper/background (Message 1 to 10 of 10)  
From: John Smith
Subject: Wallpaper/background
Date: 20 Nov 2002 18:23:57
Message: <3ddc198d@news.povray.org>
Is there a provision in POVRay for using a wallpaper (an image) for the
background. That is, I would like to reference a bitmap that would match the
viewport size and orientation no matter how I move the camera. No shadows or
lighting on it either.
Thanks.


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From: hughes, b 
Subject: Re: Wallpaper/background
Date: 20 Nov 2002 18:45:53
Message: <3ddc1eb1@news.povray.org>
"John Smith" <me### [at] nospamcom> wrote in message
news:3ddc198d@news.povray.org...
> Is there a provision in POVRay for using a wallpaper (an image) for the
> background. That is, I would like to reference a bitmap that would match
the
> viewport size and orientation no matter how I move the camera. No shadows
or
> lighting on it either.

You could use Screen.inc, found in the includes directory (folder), to keep
a image file showing in the camera frame. It was made to fix elements into
the view, although I don't know of any example of a fixed background. It
would need to be large and more distant than any other scene element, with a
ambient 1 diffuse 0 in the finish statement of the texture used as the
image_map.

Preventing shadows would probably require that you light_group the whole
scene yet leave the background plane out of that grouping.

--
Farewell,
Bob


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From: Christopher James Huff
Subject: Re: Wallpaper/background
Date: 20 Nov 2002 19:29:32
Message: <chrishuff-7AFC4F.19275020112002@netplex.aussie.org>
In article <3ddc1eb1@news.povray.org>,
 "hughes, b." <omn### [at] charternet> wrote:

> Preventing shadows would probably require that you light_group the whole
> scene yet leave the background plane out of that grouping.

It only requires setting diffuse to 0 and ambient to 1.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


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From: Philippe Debar
Subject: Re: Wallpaper/background
Date: 20 Nov 2002 19:56:03
Message: <3ddc2f23$1@news.povray.org>
"Christopher James Huff" <chr### [at] maccom> wrote in message
news:chr### [at] netplexaussieorg...
> In article <3ddc1eb1@news.povray.org>,
>  "hughes, b." <omn### [at] charternet> wrote:
>
> > Preventing shadows would probably require that you light_group the whole
> > scene yet leave the background plane out of that grouping.
>
> It only requires setting diffuse to 0 and ambient to 1.

That only prevents shadows on the object.

If you want also to prevent shadows from the wallpaper onto the other
objects, use no_shadow (it is not a finish thing like diffuse and ambient,
but an object modifier).


(BTW, does anybody know of a way to use this kind of setting in a radiosity
scene but to have no lighting from the image on the rest of the scene, as
ambient 1 is bond to produce ?)


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From: Christopher James Huff
Subject: Re: Wallpaper/background
Date: 20 Nov 2002 22:04:33
Message: <chrishuff-D3859A.22025120112002@netplex.aussie.org>
In article <3ddc2f23$1@news.povray.org>,
 "Philippe Debar" <phd### [at] wanadoobe> wrote:

> That only prevents shadows on the object.
> 
> If you want also to prevent shadows from the wallpaper onto the other
> objects, use no_shadow (it is not a finish thing like diffuse and ambient,
> but an object modifier).

Shadows could only be cast on something behind the object from the light 
source's point of view. If the "background" is behind everything, 
including light sources...
Making it shadowless would probably slightly speed shadow calculations 
up though.


> (BTW, does anybody know of a way to use this kind of setting in a radiosity
> scene but to have no lighting from the image on the rest of the scene, as
> ambient 1 is bond to produce ?)

Some kind of no_radiosity flag might be useful, I don't know of any way 
to do this now. Save radiosity data from a rendering without the object, 
render with always_sample off with the object?
This really isn't a suitable technique for a background anyway, the only 
use I can think of would be for modelling an object from a reference 
image. Reflections and refractions just don't work with it. The best 
alternative would be a sky_sphere.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


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From: hughes, b 
Subject: Re: Wallpaper/background
Date: 21 Nov 2002 01:56:47
Message: <3ddc83af@news.povray.org>
"Christopher James Huff" <chr### [at] maccom> wrote in message
news:chr### [at] netplexaussieorg...
> In article <3ddc1eb1@news.povray.org>,
>  "hughes, b." <omn### [at] charternet> wrote:
>
> > Preventing shadows would probably require that you light_group the whole
> > scene yet leave the background plane out of that grouping.
>
> It only requires setting diffuse to 0 and ambient to 1.

Oops, yeah. No diffuse , no contribution from light sources.


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From: Philippe Debar
Subject: Re: Wallpaper/background
Date: 21 Nov 2002 05:02:57
Message: <3ddcaf51@news.povray.org>
Christopher James Huff wrote:
> Shadows could only be cast on something behind the object from the light 
> source's point of view. If the "background" is behind everything, 
> including light sources...
> Making it shadowless would probably slightly speed shadow calculations 
> up though.

I was still thinking radiosity, with a sky_sphere giving off light.


About the unwanted backdrop-lighting-the-scene problem, I have thought 
of two possible solutions :

* backdrop alone  in a light_group (but I do not know if this works with 
ambient light emmission in radiosity).

* use a no_image, no_reflection clone with ambient -1 (but I fear ugly 
lighting artifacts)

Povingly,

Philippe


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From: Christopher James Huff
Subject: Re: Wallpaper/background
Date: 21 Nov 2002 11:45:17
Message: <chrishuff-3A3582.11433921112002@netplex.aussie.org>
In article <3ddcaf51@news.povray.org>,
 Philippe Debar <phd### [at] wanadoobe> wrote:

> * backdrop alone  in a light_group (but I do not know if this works with 
> ambient light emmission in radiosity).

I don't think that will have any effect at all.


> * use a no_image, no_reflection clone with ambient -1 (but I fear ugly 
> lighting artifacts)

No need for a -1 ambient, a plain black texture with ambient and diffuse 
0 should do to hide the backdrop from radiosity, assuming no_image 
doesn't also make it invisible to radiosity. As I mentioned though, a 
better solution would just be to not use a backdrop, you'll never get 
correct radiosity, reflections, or refraction that way. A sky_sphere is 
a much better choice.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


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From: gonzo
Subject: Re: Wallpaper/background
Date: 21 Nov 2002 16:15:09
Message: <web.3ddd4c7254c2b915a0c272b50@news.povray.org>
Christopher James Huff wrote:
>In article <3ddcaf51[at]news.povray.org>,
> Philippe Debar <phd### [at] wanadoobe> wrote:
>
>> * backdrop alone  in a light_group (but I do not know if this works with
>> ambient light emmission in radiosity).
>
>I don't think that will have any effect at all.
>

I just did this in a scene I'm working on and it seemed to work fine. I had
a background that I wanted to illuminate with a colored light, but didn't
want the colored light or background to influence the radiosity, so I made
the light & background a light_group with global lights turned off, and it
seems to do exactly what I wanted.


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From: Christopher James Huff
Subject: Re: Wallpaper/background
Date: 22 Nov 2002 12:28:01
Message: <chrishuff-6BEAF4.12262222112002@netplex.aussie.org>
In article <web.3ddd4c7254c2b915a0c272b50@news.povray.org>,
 "gonzo" <rgo### [at] lansetcom> wrote:

> I just did this in a scene I'm working on and it seemed to work fine. I had
> a background that I wanted to illuminate with a colored light, but didn't
> want the colored light or background to influence the radiosity, so I made
> the light & background a light_group with global lights turned off, and it
> seems to do exactly what I wanted.

An object isn't a light though...this is the right way to make sure the 
light only directly illuminates the backdrop, but it shouldn't have any 
effect on radiosity. I suspect it just doesn't show a visible effect in 
your scene.

Again, this kind of camera-aligned backdrop is useless for any kind of 
realistic effect. The background should give a radiosity effect, and 
should show up in reflections or refractions, so it needs to surround 
the whole scene. You might be able to use a sky_sphere with the same 
general color of the backdrop, and a random pattern that will look "good 
enough" in reflections. Then the radiosity of the real backdrop won't 
matter much, and the lighting of the scene will be closer to correct.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


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