Hi/Hello

Recently, I've been modifying a scene I created some time ago that outputs the
following image:
https://www.ant01.fr/images/imgAnt01/povray/radarKaboom_1280.png

which is inspired from this image:
https://www.universetoday.com/wp-content/uploads/2013/03/IMG_3857a_KaBOOM-at-KSC_Ken-Kremer.jpg

I tried to get shadows that are brighter like on the source image but the only
trick that works for that purpose was to add a second light source with the
'shadowless' keyword (inspired a little from three light point sources technique
for 3d scenes, the shadowless light source is on the side of the sene by
comparison with the light that casts shadows). I tried with a single light
source with the following for the color: 'color srgb <1, 1, 0.95>*1.2' but the
resulting shadows are too black. Of course all this imply using radiosity, so
the ambient value must be set to 0 (I use the 3.8 version of povray, so I don't
need to set ambient values to 0 with the '#default' keyword. I saw on the povray
radiosity wiki page that recursion_limit can change the indirectly-lit object
but I didn't see any changes by setting this value to 3 or 4

So my question is how do you get bright shadows with radiosity ? Do you use
several light sources or do you have others techniques ?

Post a reply to this message

"Warren" <nomail@nomail> wrote:
> Hi/Hello
>
> Recently, I've been modifying a scene I created some time ago that outputs the
> following image:
> https://www.ant01.fr/images/imgAnt01/povray/radarKaboom_1280.png

Holy crap.   I had to double/triple take to verify that THAT wasn't a photo...


> So my question is how do you get bright shadows with radiosity ? Do you use
> several light sources or do you have others techniques ?

You're trying to widen the penumbral shadow, so maybe try an area light, or a
sky sphere that has emission in the finish.  Something like that.

Really, really nice work, Warren.  :)

My inner POV-Ray devil is dancing on my shoulder and cackling, "Tell him to do
that as a NIGHT SCENE!!!"   ;)

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"Bald Eagle" <cre### [at] netscapenet> wrote: [...]

Thank you for your answer and the positive appreciation :-D. I will try the
emission finish argument and the area light components. By the way, if you like
that still, I have some more images/stills on my web site here:

https://www.ant01.fr/index.php/creation/images-povray

For the instance the only archive files corresponding to the two stills, that
can be downloaded are:
-Wild jungle river
-KaboomRadar
(just click on the corresponding still thumbnail then search the link on the
newly open page)

The other stills don't have sources download yet, but I' m currently uploading
them day after day for those who want to render them in local (the first source
available was uploaded last october 2).

Unfortunately some pov or inc files have french 'Values names'/comments. I only
started to write all in english (or at least I tried :-( ) one or two years ago.
After all, the keywords in POVRay are all in english and english is the offical
computing language nowadays.

Post a reply to this message

"Warren" <nomail@nomail> wrote:
> "Bald Eagle" <cre### [at] netscapenet> wrote: [...]
>
> Thank you for your answer and the positive appreciation :-D. I will try the
> emission finish argument and the area light components.

Sure thing  :)
I think it's the subject matter and the cloudless sky that really make it so
hard to immediately tell it's a render.

I just posted a scene for Josh where I needed to soften the well-defined shadows
- you could look at that and see how the lighting and finish affects the
shadows.

That's the other thing you can do - add "finish {diffuse #.#}" to your texture
and that ought to lighten up the shadows significantly.

> By the way, if you like
> that still, I have some more images/stills on my web site here:
>
> https://www.ant01.fr/index.php/creation/images-povray
>
> For the instance the only archive files corresponding to the two stills, that
> can be downloaded are:
> -Wild jungle river
> -KaboomRadar
> (just click on the corresponding still thumbnail then search the link on the
> newly open page)

Nice.   The island scene reminds me a bit of what I was trying to work out in
rendering Fearing Island from the Tom Swift Jr. series.   Still need to work on
some of the heightfield stuff and develop a good workflow for processing meshes
of things like helicopters and boats and airplanes....


> Unfortunately some pov or inc files have french 'Values names'/comments. I only
> started to write all in english (or at least I tried :-( ) one or two years ago.
> After all, the keywords in POVRay are all in english and english is the offical
> computing language nowadays.

Well your English is probably just as good - possibly better than mine  ;)
I grew up speaking American english, and haven't ever really _studied_ it.  So
there were often foreign students in graduate school who had a much better grasp
of things like "split infinitives" and other things that I never concerned
myself with.  :D

I had to do a fair amount of digging in the old chemical literature - where
German was the "official chemistry language" for a long time, so I know the
feeling.  Nothing like puzzling over how to make a pyrilium salt from a
Chemische Berichte paper that the librarian obtained for me through
inter-library loan from "the archives" - published in ... 1874, when bonding
theory and all sorts of things weren't exactly completely worked out...
"They want me to do what...?   With a what...?"   :O

Some things in POV-Ray are still like that for me.  :D   ;)

Post a reply to this message

Le 2019-10-06 à 07:07, Warren a écrit :
> Hi/Hello
> 
> Recently, I've been modifying a scene I created some time ago that outputs the
> following image:
> https://www.ant01.fr/images/imgAnt01/povray/radarKaboom_1280.png
> 
> which is inspired from this image:
>
https://www.universetoday.com/wp-content/uploads/2013/03/IMG_3857a_KaBOOM-at-KSC_Ken-Kremer.jpg
> 
> I tried to get shadows that are brighter like on the source image but the only
> trick that works for that purpose was to add a second light source with the
> 'shadowless' keyword (inspired a little from three light point sources technique
> for 3d scenes, the shadowless light source is on the side of the sene by
> comparison with the light that casts shadows). I tried with a single light
> source with the following for the color: 'color srgb <1, 1, 0.95>*1.2' but the
> resulting shadows are too black. Of course all this imply using radiosity, so
> the ambient value must be set to 0 (I use the 3.8 version of povray, so I don't
> need to set ambient values to 0 with the '#default' keyword. I saw on the povray
> radiosity wiki page that recursion_limit can change the indirectly-lit object
> but I didn't see any changes by setting this value to 3 or 4
> 
> So my question is how do you get bright shadows with radiosity ? Do you use
> several light sources or do you have others techniques ?
> 
> 
> 
One thing that you can do :
Have a sky_sphere with the sky as you like it.

sky_sphere{pigment{Your_Sky_Pigment}}

Now, add a large sphere around your scene, Give it the same texture as 
your sky_sphere, but with a high emission finish :

sphere{0,1 // So that you don't need to scale your pigment
  pigment{Your_Sky_Pigment}
  finish{diffuse 0 emission 3}
  // Don't interact with lights, but make it bright !
  scale 10000 // make it large
  hollow // to remove a warning and allow the use of media & fog
  no_image no_reflection // So that it don't show
}

That's not the only option.

Post a reply to this message

Op 06/10/2019 om 21:48 schreef Alain Martel:
> Le 2019-10-06 à 07:07, Warren a écrit :
>> Hi/Hello
>>
>> Recently, I've been modifying a scene I created some time ago that 
>> outputs the
>> following image:
>> https://www.ant01.fr/images/imgAnt01/povray/radarKaboom_1280.png
>>
>> which is inspired from this image:
>>
https://www.universetoday.com/wp-content/uploads/2013/03/IMG_3857a_KaBOOM-at-KSC_Ken-Kremer.jpg

>>
>>
>> I tried to get shadows that are brighter like on the source image but 
>> the only
>> trick that works for that purpose was to add a second light source 
>> with the
>> 'shadowless' keyword (inspired a little from three light point sources 
>> technique
>> for 3d scenes, the shadowless light source is on the side of the sene by
>> comparison with the light that casts shadows). I tried with a single 
>> light
>> source with the following for the color: 'color srgb <1, 1, 0.95>*1.2' 
>> but the
>> resulting shadows are too black. Of course all this imply using 
>> radiosity, so
>> the ambient value must be set to 0 (I use the 3.8 version of povray, 
>> so I don't
>> need to set ambient values to 0 with the '#default' keyword. I saw on 
>> the povray
>> radiosity wiki page that recursion_limit can change the indirectly-lit 
>> object
>> but I didn't see any changes by setting this value to 3 or 4

For open air scenes, recursion_limit can/should stay at 1; it is only 
useful to increase it for indoor scenes. Be aware that render time 
increases also somewhat in that case.

>>
>> So my question is how do you get bright shadows with radiosity ? Do 
>> you use
>> several light sources or do you have others techniques ?
>>
>>
>>
> One thing that you can do :
> Have a sky_sphere with the sky as you like it.
> 
> sky_sphere{pigment{Your_Sky_Pigment}}
> 
> Now, add a large sphere around your scene, Give it the same texture as 
> your sky_sphere, but with a high emission finish :
> 
> sphere{0,1 // So that you don't need to scale your pigment
>   pigment{Your_Sky_Pigment}
>   finish{diffuse 0 emission 3}
>   // Don't interact with lights, but make it bright !
>   scale 10000 // make it large
>   hollow // to remove a warning and allow the use of media & fog
>   no_image no_reflection // So that it don't show
> }
> 
> That's not the only option.

indeed, but yours is an easy and fast solution.

Otherwise, in the radiosity block, if you have not done so, switch 
'normal' and/or 'media' to 'on' (off by default).

-- 
Thomas

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Thanks to everybody for the hints ! I have less dark shadows now. You can see
the
result here on my web site (I replaced the "M1 Abrams" tank with a Jeep) :

https://www.ant01.fr/index.php/creation/16-creation-povray/28-radarkaboom

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