TITLE: Ghost Light
NAME: Bill Pragnell
COUNTRY: UK
EMAIL: billpragnell@hotmail.com
WEBPAGE: http://www.infradead.org/~wmp/
TOPIC: Absence
COPYRIGHT: I SUBMIT TO THE STANDARD RAYTRACING COMPETITION COPYRIGHT.
JPGFILE: wp_ghost.jpg
ZIPFILE: wp_ghost.zip
RENDERER USED: 
    MegaPOV 1.21

TOOLS USED: 

DAZ Studio for figure pose
Blender for figure fine-tuning
PoseRay for figure conversion
InkScape for lathe splines
GIMP for image map preparation

RENDER TIME: 
    4 hours for first radiosity pass, 8 hours for final render

HARDWARE USED: 
    MacBook 1.8GHz 512MB RAM

IMAGE DESCRIPTION: 

Is a ghost a presence? Or an absence? Even if it is a presence, it must
signify somebody's absence. Perhaps if I were absent through death, but
sill present in some form, I would have a brief look at my absence. Perhaps
I wouldn't. Perhaps I would remain absent. This young woman, however, is
clearly inspecting her absence with great interest...


DESCRIPTION OF HOW THIS IMAGE WAS CREATED: 

My starting point for this image is fairly unique; I typed the topic,
'Absence', into Google Images, and one of the first hits was a picture of
an empty armchair. The rest followed from there... :)

The chair, table, sideboard, shelves, walls, fireplace, fire grate,
ashtray, lamp, mirror-ball and picture frames were all built using normal
CSG techniques (with rounded edges where possible). I wrote a macro to
build picture frames given an arbitrary cross-section object. The pictures
are adapted from my own photographs to avoid permission issues - the
panorama is a Scottish loch and the sepia print is Venice, Italy (both
pictures I took whilst on holiday earlier this year). The small picture on
the mantelpiece is actually Aiko herself, screen-grabbed from the DAZ
Studio viewport.

The bottles, vases and wineglass are all lathes employing bezier splines
created using the excellent InkScape. The bottle labels are image_maps of
random wine labels downloaded with the help of Google Images (I can't
remember the sources, so I can't credit them... but you can't really see
them well enough to tell what they are, anyway).

The books on the shelves are of two types, generated using my own book
macro. The paperbacks have randomly generated titles and authors (taken
from text files of names and likely title vocabulary), with semi-random
colours. The hardbacks are much more regular.

The ghost is my crowning achievement of this image, and is something I'm
extremely proud of. I took the standard Aiko 3 model and posed her in Daz
Studio. Then I ran her through PoseRay to remove all unnecessary mesh
components (tongue, teeth etc), not to mention the zero-thickness add-ons
(eyelashes, pubic hair etc). Next, I imported the resulting wavefront
object into Blender, homogenised the mesh, and properly closed the
remaining open sections (mouth and eye sockets). Then I exported two
versions of the resulting mesh to POV-Ray: one unchanged, and one very
slightly shrunk along its normals. Putting a hollow version of the former
around an opaque version of the latter and filling it with emissive media
provided the glowing 'skin' effect. The hair was exported from DAZ Studio
as a separate object, and extruded in Blender to produce a closed volume,
which was then exported to POV-Ray and also filled with media.

There are no light sources in this scene; it is lit entirely using
radiosity. The lighting in general has been a real headache, and I'm not
really satisfied with it at all. I originally used area_lights inside the
ghost, but the size and proximity to some of the objects caused strange
shadow problems... and the render time was extortionate. In the end I spent
over two weeks playing with radiosity techniques, and I've basically run
out of time. The submitted image is the best I can do, and it's far from
perfect: it looks ok, but on high-gamma displays (or after correction) the
darker areas (under the sideboard, around the shelves) exhibit some really
prominent artifacts. Even the brightly lit areas show a fair amount of
splotchiness, although this isn't so bad due to the obviously irregular
nature of the light source... It's difficult to know how to improve it
further, because the radiosity settings are already really silly - count is
maxed out for both passes, error_bound is 0.02, minimum_reuse is
miniscule and the first pass had to be performed at full resolution in
order to catch all the shadowed areas. I think the way forward is to
combine a small area_light with the radiosity and employ a much higher level
of smoothing in the final pass. This will take a very long time to render,
and the results will eventually be posted on my website (see above).

A note on the zip file: I've tried to supply everything needed to
reproduce the picture, including the ghost geometry include files produced
by PoseRay (these are very large). I haven't included the BillMacros.inc
file, but the only macro needed from this is the RoundedBox() macro, other
versions of which can be found elsewhere. Or just replace it with a normal
Cube. Obviously both radiosity passes will also need to be performed.


