---- DATABASE ERROR ----Quick And Dirty: Good Enough Clouds
by Mike Kost
Introduction
Clouds are one of the trickier environment objects to render well in
Povray. Convincing clouds require media effects and long rendering
times, which is annoying when clouds are not a primary component of the
rendering. Sometimes good enough is, well, good enough. This Quick and
Dirty tutorial will show how to get some "good enough" clouds using
Povray 3.6.
When Is Good Enough Good Enough?
So when is good enough good enough? I've often wanted some clouds in
the sky to reflect off water or the infamous reflective sphere on a
plane to add some character to my rendered scene. In these cases, I
don't need a full-blown, high quality media cloud - I need something
that'll render quickly and look good enough in a reflection. Take the
scene below, example1.pov, - a few
clouds would liven up the reflection
off the sphere.
Layers Of Planes
To get quick rendering times, the first rule is make a texture and slap
it onto something. This is how my early clouds started out, but they
lacked depth and color variation that make real clouds look amazing. To
get that depth and color variation, add multiple layers of planes. With
the added planes, the clouds get true depth while allowing color or
ambient finish variations between the layers to add some complexity to
the rendering. The easiest way is build this is to declare a cloud
pigment P_Cloud and apply it onto my layers of planes.
The plane layers look something like this:
union {
plane {
<0, -1, 0> 0
texture { pigment { P_Cloud
} finish { ambient 1.0 } }
}
plane {
<0, -1, 0> 0
translate <0, 5, 0>
texture { pigment { P_Cloud
} finish { ambient 0.6 } }
}
plane {
<0, -1, 0> 0
translate <0, 10, 0>
texture { pigment { P_Cloud
} finish { ambient 0.8 } }
}
plane {
<0, -1, 0> 0
translate <0, 15, 0>
texture { pigment { P_Cloud
} finish { ambient 0.4 } }
}
translate <0, 1000, 0> // Put in correct space
in sky
}
It is important to translate the individual planes before applying the
texture. If the texture is applied, and then the planes are put in
their relative positions, they will all have the same pigment applied
since they were all at y=0. In this example, I've varied the ambient
finish values to change how dark or light the clouds look.
Adjusting P_Cloud
By creating our cloud layers with planes, we've pushed the problem into
our P_Cloud pigment. Generally, my P_Cloud's take some form similar to
#declare P_Cloud = pigment {
bozo
turbulence <1,1,1>
octaves 6
lambda 2
omega 0.5
color_map {
[0.00 color rgbt
<1.00,1.00,1.00,1.00>]
[0.45 color rgbt
<1.00,1.00,1.00,1.00>]
[0.55 color rgbt
<0.50,0.50,0.50,0.50>]
[0.00 color rgbt
<1.00,1.00,1.00,0.00>]
}
scale 1000
}
To get a P_Cloud that feel right for my rendering, I create a dummy
Povray file, observe_clouds.pov,
and render it several times, tweaking parameters each rendering. The
Povray file includes a sky_sphere to create the blue sky, the plane
layers, and my P_Clouds declaration. I have it look directly at the
clouds to get a feel for what the reflection will see. When I want to
hit the problem over the head, I use my POV-Broom
scripts to do batch renderings. I ended up with the following clouds
after playing with my settings.
The source for P_Clouds is shown below:
#declare P_Cloud = pigment {
wrinkles
turbulence <0.5, 0.5, 0.5>
octaves 7
omega 0.5
lambda 3
color_map {
[0.00 color rgbt
<1.00,1.00,1.00,1.00>]
[0.50 color rgbt
<1.00,1.00,1.00,1.00>]
[0.60 color rgbt
<0.50,0.50,0.50,0.50>]
[1.00 color rgbt
<1.00,1.00,1.00,0.00>]
}
scale <1200,1200,1200>
}
Putting It Together
After getting the clouds the way I want them, I insert the cloud layer
and P_Clouds into my original. The new example2.pov
renders and gives
reasonable cloud reflections in the sphere.
Want To Know More?
Using multiple planes to create clouds is well discussed in the Povray
community, and a few people have additional information on making
clouds.
Last Edited: 11/15/04
Copyright (C) 2004 Mike Kost