i see fog type 1 and 2 for constant and "from the floor" respectively.

i take that to mean a fog that recedes from the viewer needs some manipulation
of the scene, i.e. so it is flipped 90 degrees using fog_type 2?

-bryan

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"CapitalSpace" <bry### [at] gmailcom> wrote:
> some manipulation
> of the scene, i.e. so it is flipped 90 degrees using fog_type 2?

i am trying the up vector - seems like this should do it - but looks weird, e.g:

up <0, 0, -1>
or
up <0, 0, 1>

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On 09/15/2010 03:39 PM, CapitalSpace wrote:
> i see fog type 1 and 2 for constant and "from the floor" respectively.
> 
> i take that to mean a fog that recedes from the viewer needs some manipulation
> of the scene, i.e. so it is flipped 90 degrees using fog_type 2?
> 
> -bryan
> 
> 
check out:
http://wiki.povray.org/content/Documentation:Reference_Section_3.1#Fog

particular attention to "up" and transformations ... I believe a TDG
used this (see "Morning on the lake" in p.b.i)

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Jim Holsenback <jho### [at] povrayorg> wrote:
> check out:
> http://wiki.povray.org/content/Documentation:Reference_Section_3.1#Fog
>
> particular attention to "up" and transformations ...

yes, thanks it appears i have the test pov working with this.

however, my own scene has the camera with "up 39.00*y" - any caveats about
mixing the up vectors? the scene seems ok.

oh, and should fog play nicely with radiosity?

i originally wanted the fog to start from a certain point, so the foreground is
always unaffected by fog : but it seems "that's not how it works".

-bryan

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On 09/15/2010 04:42 PM, CapitalSpace wrote:
> Jim Holsenback <jho### [at] povrayorg> wrote:
>> check out:
>> http://wiki.povray.org/content/Documentation:Reference_Section_3.1#Fog
>>
>> particular attention to "up" and transformations ...
> 
> yes, thanks it appears i have the test pov working with this.
> 
> however, my own scene has the camera with "up 39.00*y" - any caveats about
> mixing the up vectors? the scene seems ok.

hmmm ... Don't believe I've ever used anything other than the default
"up" in a camera definition. Perhaps with such a large up vector you
might be having a granularity issue ... that is a little bit of
transformation (rotation) produces too big a change (degrees). If your
setup is something vaguely like: camera in -z looking toward +z then fog
transformation in the x (rotate) might do the trick ... rotate so that
the ground fog is below the ground plane in the foreground.

> 
> oh, and should fog play nicely with radiosity?
> 

Should ... if you have any media in containers sometimes the containers
become slightly visible if the fog intercepts

> i originally wanted the fog to start from a certain point, so the foreground is
> always unaffected by fog : but it seems "that's not how it works".
> 

Give the default camera "up" a try and experiment

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Jim Holsenback <jho### [at] povrayorg> wrote:
> If your
> setup is something vaguely like: camera in -z looking toward +z then fog
> transformation in the x (rotate) might do the trick ... rotate so that
> the ground fog is below the ground plane in the foreground.

woo hoo! this did it! i corresponded the up's like this :

camera up 39.00*y
fog up 39.00*z

and i'm a happy camper. FYI the default camera is from molscript.

thanks Jim!

-bryan

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> Jim Holsenback<jho### [at] povrayorg>  wrote:
>> check out:
>> http://wiki.povray.org/content/Documentation:Reference_Section_3.1#Fog
>>
>> particular attention to "up" and transformations ...
>
> yes, thanks it appears i have the test pov working with this.
>
> however, my own scene has the camera with "up 39.00*y" - any caveats about
> mixing the up vectors? the scene seems ok.
>
> oh, and should fog play nicely with radiosity?
>
> i originally wanted the fog to start from a certain point, so the foreground is
> always unaffected by fog : but it seems "that's not how it works".
>
> -bryan
>
>
>

Fog never interact with radiosity. As fog is not realy a media, adding 
media on have no effect. Radiosity can never illuminate any media, and 
even less fog. No light source can illuminate a fog ether.

Ground fog never goes to zero density, the density fall off as the 
inverse square of the altitude. Any area under fog_offset is constant.
If you want to exclude an area, you need to use a non-hollow plane. If 
the camera is inside that plane, you need to diference a sphere from the 
plane around the camera so that the camera is not inside a non-hollow 
object.



Alain

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"CapitalSpace" <bry### [at] gmailcom> wrote:
>
> woo hoo! this did it! i corresponded the up's like this :
>
> camera up 39.00*y
> fog up 39.00*z
>
> and i'm a happy camper. FYI the default camera is from molscript.
>
> thanks Jim!
>

Ah, so *that's* how it's done: changing the fog's up vector is the key. (I never
could get such a thing to work by just *rotating* the ground fog. No wonder!)
Re-reading the documentation, I see that the explanation is there, clear as day.
I don't know how I missed that.

Ken

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Alain <aze### [at] qwertyorg> wrote:


> ...If you want to exclude an area, you need to use a non-hollow plane. If
> the camera is inside that plane, you need to diference a sphere from the
> plane around the camera so that the camera is not inside a non-hollow
> object.
>

Another clever idea, worth trying. Thanks, Alain.

Ken

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Am 16.09.2010 18:55, schrieb Alain:

>> oh, and should fog play nicely with radiosity?
>
> Fog never interact with radiosity. As fog is not realy a media, adding
> media on have no effect. Radiosity can never illuminate any media, and
> even less fog. No light source can illuminate a fog ether.

However, the other way round, fog /does/ affect radiosity; the fog will 
effectively appear to "illuminate" the scene.

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