hello, I'm a new user and for a project in class we're creating a scene of our
choice, I want to create a scene of a storm, with lightning hiting the ground,
a tornado and storm clouds in the sky. How could I create this?
thank you

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> hello, I'm a new user and for a project in class we're creating a scene of our
> choice, I want to create a scene of a storm, with lightning hiting the ground,
> a tornado and storm clouds in the sky. How could I create this?
> thank you
> 
> 
> 

That looks like an ambitious, and time consuming, project for someone 
that is learning.

For the clouds, normaly, you'd use some object filled with a mesia and 
use some pattern or function to modulate that media. The media to use in 
this case, is a scattering media. Watch out, your render time will get 
prety long. NEVER use the "intervals" keyword. Use "samples" instead to 
get smoother results. Keep it low during the early stages to keep the 
render times needed during the devlopment phase to a reasonable level. 
Increace the samples count for your close to and final renders.

For the lightning, you can also use some media, but emissive media. Use 
a cylinder filled with emissive media that use the cylindrical pattern 
to whitch you apply some turbulence. For this, you need to create the 
container around the origin then rotate, scale and translate it to the 
desired location.
Emissive media is the fastest rendering media.
Emissive media don't illuminate it's surrounding, it's just visible 
without any light shining on it nor any background to see it against.

If you want your lightning to illuminate the area, then, you'll need to 
add some light_source along it's path. Be sure to make those light 
fading light by adding fade_power 2 and fade_distance <some distance> to 
the deffinitions. (that's the "fast" way, but less acurate)
The Slow, but more acurate, way is to use radiosity with the "media on" 
option. This way, the emissive media can actualy illuminate it's 
surrounding. But, as I said, radiosity is slow! Also, there are many 
settable parameters whose function and effects are not always obvious or 
easy to set.

Now, the trick is to create and locate the containers to create your 
clouds, find the best, to your taste, pattern for the clouds. Tweak the 
turbulence to give your clouds a more convincing look.

You'll probably need a complex container filled by several medias and 
also, possibly medias with more than one dencitys.

If you are tight on time, may I suggest looking to some other kind of 
scene...



Alain

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"mhc91" <nomail@nomail> wrote in message 
news:web.4a64b0da304dff418e079a6f0@news.povray.org...
> hello, I'm a new user and for a project in class we're creating a scene of 
> our
> choice, I want to create a scene of a storm, with lightning hiting the 
> ground,
> a tornado and storm clouds in the sky. How could I create this?
> thank you
>

As Alain said, this is ambitious for someone new to POV-Ray, but that's not 
necessarily a bad thing, it depends how much time and energy you've got.

I'd say that there are some easier approaches than using media, although 
media would probably give the best results, I would argue that it's easier 
to learn if you keep the render times as short as possible, so that you can 
do more test renders.

There are various tutorials for creating clouds on the Internet, though 
storm clouds are likely to be quite tricky. The example below just uses a 
simple 'wrinkles' pattern with turbulence for the clouds (but doesn't look 
very stormy)l.

For the lightning I'd recommend butting together some simple thin cone 
shapes. Turn the ambient setting up high for the lightning cones and down 
for everything else to give quite a moody feel.

The simple example below may serve as a starting point. It uses 3 white 
cones with ambient turned up high. There are 5 lights distributed up the 
middle of the lightning object using 'fade' settings to prevent the light 
from travelling very far. The no_shadow keyword on the lightning object 
enables light to pass out and prevents the cones from casting shadows on 
other objects in the scene.

I've used RGB values to specify colours here. If you prefer to use the names 
of predefined colours you should add:

#include "colors.inc"



camera {location <0, 1, -5> look_at <0,2,0>}
#declare MyLightSource = light_source {<0,0,0> color rgb 2
  fade_distance 0.4
  fade_power 2
}

// Lightning
union {
  cone {<0,0,0>,0.00,<3,3,3>,0.02}
  cone {<3,3,3>,0.01,<1,6,1>,0.03}
  cone {<2,1,0>,0.00,<2,2,2>,0.01}
  no_shadow
  pigment {rgb 1}
  finish {ambient 2}
}

// Lights inside the lightning object
light_source {MyLightSource}
light_source {MyLightSource translate <1,1,1>}
light_source {MyLightSource translate <3,3,3>}
light_source {MyLightSource translate <2,1,0>}
light_source {MyLightSource translate <1,5,1>}


// Ground
plane {y,-0.1 pigment {rgb <0,0.2,0>} finish {ambient 0}}

// Sky
plane {y,5.2
  finish {ambient 0}
  pigment {
    wrinkles
    turbulence <0.5, 0.5, 0.5>
    octaves    7
    omega      0.5
    lambda     3
    color_map {
      [0.0 color rgb <1.00,1.00,1.00>]
      [0.4 color rgbt 1]
      [0.5 color rgbt 1]
      [1.0 color rgb <1.00,1.00,1.00>]
    }
  }
}




Regards,
Chris B.

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Alain <aze### [at] qwertyorg> wrote:
> For the lightning, you can also use some media, but emissive media. Use
> a cylinder filled with emissive media that use the cylindrical pattern
> to whitch you apply some turbulence. For this, you need to create the
> container around the origin then rotate, scale and translate it to the
> desired location.

You may also want to give it a more distinctly zig-zagging appearance, by using
multiple such cylinders touching at their ends, using rand() in a smart fashion
to pick the in-between points more or less randomly.


> If you want your lightning to illuminate the area, then, you'll need to
> add some light_source along it's path. Be sure to make those light
> fading light by adding fade_power 2 and fade_distance <some distance> to
> the deffinitions. (that's the "fast" way, but less acurate)

Note that this *may* give bands in shadows; if you want to avoid these, using a
series of well-placed 1-dimensional "area" lights with the "jitter" keyword may
help.


> The Slow, but more acurate, way is to use radiosity with the "media on"
> option. This way, the emissive media can actualy illuminate it's
> surrounding. But, as I said, radiosity is slow! Also, there are many
> settable parameters whose function and effects are not always obvious or
> easy to set.

Note that a lightning will probably be too thin to be captured by radiosity
effectively, resulting in ugly blotchy lighting.


> If you are tight on time, may I suggest looking to some other kind of
> scene...

Yup - I definitely second this advice.

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