Hello, everyone. I've been using POVRay for 5-10 of the 13 years that I've
lived now, and I ran into a great buttress of a problem with the scene I've
been recently working on. This problem is so unusual that I'm now executing
what I had earlier held as a last resort: registering here on the newsgroup
to ask you people (Don't worry, it's nothing personal. ;-) ).

Here's my problem. I have the camera in a dark room, facing a window. I need
heavy rain on the outside of the window, and a lightning flash shining in
through the window.

I tried an excessively bright point light outside the window for the
lightning, and I tried reflection with a bozo normal _on_ the window for
the rain, but those both take it in the entirely wrong direction. I sifted
through the tenuousness of Google searches already, but I uncovered nothing
save Chambers' dandelion
(http://news.povray.org/povray.binaries.images/thread/%3C43fe52d0@news.povray.org%3E/).
The problems with following how Chambers
accidentally made it look like rain on the window are various:
 1): His looked like light rain, not heavy rain.
 2): His window was at a tight angle, and mine is straight on. I imagine
that would make a difference.
 3): He has things outside the window in the background, whereas I have
nothing but the lightning flash.

Can any of you help me figure out how to go about this?

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"Quartz" <nomail@nomail> wrote in message
news:web.442c0a2541c1995dfd52120@news.povray.org...
> Hello, everyone. I've been using POVRay for 5-10 of the 13 years that I've
> lived now, and I ran into a great buttress of a problem with the scene I've
> been recently working on. This problem is so unusual that I'm now executing
> what I had earlier held as a last resort: registering here on the newsgroup
> to ask you people (Don't worry, it's nothing personal. ;-) ).
>
> Here's my problem. I have the camera in a dark room, facing a window. I need
> heavy rain on the outside of the window, and a lightning flash shining in
> through the window.
>
> I tried an excessively bright point light outside the window for the
> lightning, and I tried reflection with a bozo normal _on_ the window for
> the rain, but those both take it in the entirely wrong direction. I sifted
> through the tenuousness of Google searches already, but I uncovered nothing
> save Chambers' dandelion
>
(http://news.povray.org/povray.binaries.images/thread/%3C43fe52d0@news.povray.or
g%3E/).
> The problems with following how Chambers
> accidentally made it look like rain on the window are various:
>  1): His looked like light rain, not heavy rain.
>  2): His window was at a tight angle, and mine is straight on. I imagine
> that would make a difference.
>  3): He has things outside the window in the background, whereas I have
> nothing but the lightning flash.
>
> Can any of you help me figure out how to go about this?

Do you mean you want the lightning flash to "light up" the rain on the window?

If so, the main thing that causes this to happen in real life is of course all
of the tiny droplets refracting the lightning strike, so with that in mind you
need a very strong normal or an isosurface that models the thousands of
droplets, and then a very bright object to refract, as well as a bright light to
create specular highlights on all of the droplets.

In this example a big white box represents the visible lightning, and a light
adds to the specular highlights on the (poorly modelled) rain drops.  (render
with AA enabled)

camera {location <0,0,-3> look_at <0,0,0>}
light_source {<-5,3,-10> rgb <0.8,0.8,1>*10}
box {<-1,-1,-0.05> <1,1,0>
 texture {
  pigment {color rgbf <1,1,1,0.7>}
  finish {specular 1 roughness 0.001 ambient 0 diffuse 0 reflection 0.1}
  normal {
   bumps
   slope_map {
    [0 <0,0>]
    [0.95 <0,1>]
    [1 <0.1,1>]
   }
  }
  scale <0.02,.1,.1>*.3
  rotate <45,0,0>
 }
 interior {ior 1.5}
}
box {<0,5.1,4> <-10,30,7>
 texture {
  pigment {
   gradient x
   color_map {
    [0 color rgb 1]
    [.7 color rgb <0.5,0.5,1>]
   }
  }
  finish {ambient 80}
 }
}


I hope this helps...

Cheers,

Lance.

thezone - thezone.firewave.com.au

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"render with AA enabled" -Lance Birch

.....I'm sorry, perhaps this is a stupid question, since I've made myself
appear to be very good at POVRay, but what is "AA"?

"I hope this helps..." -Lance Birch

Holy whoa! I just rendered this, and it's _perfect_!! Thank you so much! :-D
Let me see now if I can adapt it to my scene...

---------------------
http://malexmedia.net/ _Media for the People_

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"Quartz" <nomail@nomail> wrote in message
news:web.442c2d5b3ce9a4dadfd52120@news.povray.org...
> "render with AA enabled" -Lance Birch
>
> .....I'm sorry, perhaps this is a stupid question, since I've made myself
> appear to be very good at POVRay, but what is "AA"?
>
>

Antialiasing

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"Antialiasing" -Ross

Oh, of course. I see. Thanks.

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.... ...This window you gave me, Lance Birch, is good, but... I can't do the
lightning flash. Whenever I try it, the sky outside looks like an overcast
day, and the light being cast on the objects in the room looks all wrong...

The light shining from the lightning flash into the room looks sharp white,
except on a green book I have on a table in front of the window. On the
book, it looks yellow, which lightning does not do. I don't know how to
simulate the lightning at all.

There are five elements here:
 1): The texture of the objects inside the room that the lightning is
shining on.
 2): The texture of the windows.
 3): The texture of the water on the outside of the windows, which Lance
Birch gave me.
 4): The pigment of the sky_sphere.
 5): The color of the light_source I'm trying to use as lightning.

Somehow I'm not using the right combinations or the right values for them,
and it's coming out wrong. I need more help. Should I post the source code
for you?

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Quartz wrote:

> .... ...This window you gave me, Lance Birch, is good, but... I can't do
> the lightning flash. Whenever I try it, the sky outside looks like an
> overcast day, and the light being cast on the objects in the room looks
> all wrong...
> 
> The light shining from the lightning flash into the room looks sharp
> white, except on a green book I have on a table in front of the window. On
> the book, it looks yellow, which lightning does not do. I don't know how
> to simulate the lightning at all.
> 
> There are five elements here:
>  1): The texture of the objects inside the room that the lightning is
> shining on.
>  2): The texture of the windows.
>  3): The texture of the water on the outside of the windows, which Lance
> Birch gave me.
>  4): The pigment of the sky_sphere.
>  5): The color of the light_source I'm trying to use as lightning.
> 
2 things about lightning

1) lightning is a very large light source. ie. it's very long
2) Lightning light is slightly blue-ish


> Somehow I'm not using the right combinations or the right values for them,
> and it's coming out wrong. I need more help. Should I post the source code
> for you?

-- 
Ger

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"Quartz" <nomail@nomail> wrote:

> The light shining from the lightning flash into the room looks sharp white,
> except on a green book I have on a table in front of the window. On the
> book, it looks yellow, which lightning does not do.

When light sources are made extra-bright, the colors of objects can get a
bit...strange. The individual RGB color values start saturating, the final
result depending on the individual color components.  A (very simple)
example would be an object with a color like <.2,1,.4>, lit by a light
source of, say, <1,1,1>*3.  Depending on the ambient and diffuse values in
the object's texture, what that does to the object's color is, very
roughly, like this: <3*.2, 3*1,3*.4>, or <.6,3,1.2>.  Since an individual
RGB color component can't be "brighter than 1" (full brightness), the
result is really <.6,1,1>--not the color you started out with.

Ken

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Thanks for all the tips, everyone. I think I've got it figured out now. :-)

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