TITLE: Kansas
NAME: Skip Talbot
COUNTRY: USA
EMAIL: skipt1@aol.com
WEBPAGE: http://www.skip.cc
TOPIC: Epic Proportions
COPYRIGHT: I SUBMIT TO THE STANDARD RAYTRACING COMPETITION COPYRIGHT.
JPGFILE: kansas.jpg
RENDERER USED: 
    POV-Ray 3.6

TOOLS USED: 
    Rhinoceros, Colefax Mesh Compression

RENDER TIME: 
    19 hours

HARDWARE USED: 
    Pentium IV 1.8 GHz 512 MB

IMAGE DESCRIPTION: 

It_s May in western Kansas, just before sunset.  The usually quiet expanse of
the Great Plains is now a world of chaos and turmoil.  Towering a thousand feet
above the ground, a black funnel cloud descends from a rotating storm base. 
The twister plows through the dusty fields just beyond a deserted farm house. 
The only witness to the event is a prairie dog, standing up at attention. 
Although he can not quite comprehend the ominous black monster lurking on the
horizon, the winds make him uneasy and he won't stray from his burrow for
long.

DESCRIPTION OF HOW THIS IMAGE WAS CREATED: 

The concept for this image is based off of my passion for storm chasing.  The
tornado depicted is similar to an F1 tornado I saw April 20 of this year in
Illinois: a dark funnel backlit by an orange sky.

The first stage in the development of this image was choosing a camera angle and
aspect ratio that would highlight the _epic proportions_ of a tornado.  A tall
image allows the funnel to fill most of the frame.  The camera is set very far
from the scene with a low lens angle so that the scaling effects of a
perspective camera aren_t quite as strong.

The funnel is composed of a mesh filled with constant density media.  After
researching many tornado funnels I learned that they have a sharp edge.  The
blurred edge is not usually caused by a density gradient but by focal blur. 
Focal blur and scattering media did not fit my render time budget so I opted
for a density function.  A sphere_sweep tornado would allow me to use spherical
density but would still be far too slow.  I also opted out of any sort of
isosurface as well.  I settled on a mesh funnel with a constant density media. 
The edges of the tornado are flared to a point simulating a density as long as
the camera is perpendicular to the funnel.

The base of the storm is a scattering media with a turbulent cylindrical density
and is meant to stimulant the ragged underside of a wall cloud, or the lowered
updraft region of a supercell thunderstorm.

The debris cloud is also scattering media.  The intersection of the funnel and
debris just would not cooperate so I rendered the image in two passes.  The
first pass being the background, funnel, and storm base, and then, without
processing, I mapped that rendering to the background of the final pass which
included the debris cloud and foreground.  The debris cloud is an isosurface
with a function density utilizing the f_helix function and turbulence warps. 
Other densities were used to keep the media contained.

A little fog thrown in for depth and to simulate the dust that gets kicked up in
the inflow winds of a storm.

I had planned for a detailed and lit foreground but I just did not have time
with work and school to put it all together.  To finish the image I reverted to
a lighting that would cast the foreground in silhouette.  Much of my image is
sacrificed as a result. However, quite a bit of work did go into the
foreground

The farmhouse and windmill were modeled in Rhinoceros with textures adequate for
the scale at which they appear in the image.  The details and textures are lost
in the silhouette, though.

The prairie dog was also modeled in Rhinoceros.  Chris Colefax_s mesh compressor
and hair macro was used to create a believable prairie dog.  However, I could
not get the lighting to work for the prairie dog in this scene, which was one
of the main reasons I had to revert to the silhouette.