TITLE: Orthonormal
NAME: Tekno Frannansa
COUNTRY: UK
EMAIL: tek@evilsuperbrain.com
WEBPAGE: http://www.evilsuperbrain.com
TOPIC: Architecture
COPYRIGHT: I SUBMIT TO THE STANDARD RAYTRACING COMPETITION COPYRIGHT.
JPGFILE: orthnorm.jpg
ZIPFILE: orthnorm.zip
RENDERER USED:
POV-Ray for Windows v3.5
TOOLS USED:
POV-Ray editor
RENDER TIME:
2 minutes 16 seconds
HARDWARE USED:
Athlon 2200 512MB RAM
IMAGE DESCRIPTION:
I've been fascinated by this kind of illusion since I was a kid, looking at
Escher's drawings. I remember thinking about it and working out that if you had
shadows or reflections or similar real-world details then the illusion would
fall apart and you'd see how it was done, so I decided to make a scene to prove
myself wrong! Everything's slightly reflective and there's lots of shadows, and
yet the image still has that wierd disorienting feel that an escher picture can
give.
Incidentally, the title "Orthonormal" is a slight abuse of a mathematical term
for a type of matrix. I felt it was appropriate because of the widespread use
of unit cubes and it's similarity to the word "abnormal" :)
Viewing reccomendation: to avoid headaches I suggest covering the right side of
the image and just looking at the left, and then revealing the left gradually.
Also it's entertaining to put it in a paint program and rotate it 180 degrees,
only the pattern on the marble changes, nothing else moves.
DESCRIPTION OF HOW THIS IMAGE WAS CREATED:
Okay, this is the spoiler. The trick is I create half a scene, with all lighting
as part of a light group, then I copy it and rotate the copy through 180
degrees around the camera's axis.
Still not clear? Okay, well there's a few things to understand here. Ignoring
shadows and reflections, a cube viewed from an angle where you can see 3 faces
looks exactly identical to an inverted cube (i.e. the 3 other faces) lit from
the opposite side, if there's no perspective. I think I just explained that
really badly! This isn't just true of cubes, lots of other shapes work just as
well, but it's easier to find situations involving "inverted" cubes.
The really simple explanation (skip this if you get it already): Think of
buttons on windows your computer pops up, notice how the top and left sides are
coloured light, and the bottom and right sides are dark? Well that's just a
convention suggesting there's some imaginary light off the top left of the
screen. The illusion works by having some things lit from that side, and some
things lit the other side so they look like pushed in buttons even though
they're not. Mix them together just right and you can't tell if you're looking
at a point on a cube that points towards you or away from you.
Now, within this system of cubes I construct a few objects that cannot be made
to look like their inverse. This gives you a few points to focus on that
clearly contradict each other, so your brain tries to find the break between
these two worlds (the up world and the down world) and when it can't you get
that strange sensation that increases sales of aspirin.
On top of that I added my website logo as a little sculpture, which I rotated so
that the "up" and "down" versions look the same as their closest counterpart,
apart from the lighting. And then I added shadows and reflections, with a lot
of tweaking to avoid the many errors that are inevitable in this kind of
scene.
I've provided the full source code, just one pov file, so you can turn on my
debug code and see where the edge is.