Original Usenet thread from alt.ascii-art, started 8 Oct 1996.
Random Dot Stereograms
alt.ascii-art
· 8 messages · 8 Oct 1996 - 22 Nov 1996
Hi! Are there any ASCII gurus out there willing to try and make an ASCII RDS? :-) I'm sure we'd all be /very/ impressed if anybody can manage it! Jonathan
Jonathan Hunter <mch...@afs.mcc.ac.uk> writes: >Hi! >Are there any ASCII gurus out there willing to try and make an ASCII >RDS? :-) >I'm sure we'd all be /very/ impressed if anybody can manage it! Well, it's not particularly easy to get decent resolution in ASCII using just dots. I have seen some nice SIRTS before -- Single-Image Random Text Stereograms. These use a field of random characters as their background. Much more common are normal SITS -- Single-Image Text Stereograms. These are stereographic ASCII line drawings. I've drawn a couple of the latter myself, but my lack of talen at ASCII in general prevented them from being very good :) -- /<-= -=-=- -= Admiral Jota =- -=-=- =->\ __/><-=- http://www.tiac.net/users/jota/ =-><\__ \><-= jot...@mv.mv.com -- Finger for PGP =-></ \<-=- -= -=- -= -==- =- -=- =- -=->/
Does anyone more talented/artistic than me (like that's difficult! :-D) have a ascii of a panther? I'm looking for a sideview, stalking. Please reply direct to me - I only check the newsgroup once a week or so. Sig-less in cyberspace, Sheena
>Jonathan Hunter <mch...@afs.mcc.ac.uk> writes: > >>Hi! >>Are there any ASCII gurus out there willing to try and make an ASCII >>RDS? :-) >>I'm sure we'd all be /very/ impressed if anybody can manage it! Here's an illustration of how it's done: . , . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I've made it easier for newbies by showing two of the dots as commas. -- John Savage koala � sydney.dialix.com.au
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In article <56a406$dc...@info.nask.pl>, gio...@warman.com.pl (Gl. Insp.
Ochrony Srodowiska) wrote:
> X X X X
--"Hi" snipped--
Awesome! Post more! Was that created manually or with the help of some software?
Fip
I just had to add to what Fipples <ful...@osu.edu (Fipples)> had to say about this. >In article <56a406$dc...@info.nask.pl>, gio...@warman.com.pl (Gl. Insp. >Ochrony Srodowiska) wrote: > >> X X X X >--"Hi" snipped-- > >Awesome! Post more! Was that created manually or with the help of some software? > >Fip I'm sorry, but just what exactly am I supposed to be looking at? Is it encoded? "I haven't lost my mind....it's backed up on hard-disk somewhere!".
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: I'm sorry, but just what exactly am I supposed to be looking
: at? Is it encoded?
Maybe this helps
Humans have two eyes, roughly Critical Design
level and separated by only a few Feature
centimetres, but it is this 'design
feature' that lets us see in three ->| |<- 6-8cm
dimensions.
|||||||
The key to stereoscopic or three / \
dimensional vision is the ability | (o) (o) |
to 'line up' the separate views of | . |
an object seen from each eye to form \ \_/ /
a single image. \_____/
Normally, when looking at something, the brain is presented with two
images, one from each eye. In order to make sense of the information it
is receiving, the brain alters the angle of the two eyes until the images
overlap. The brain then uses the muscles that surround the eyeballs to
alter their shape to create a sharp image. Using the eyeballs to provide
a sharp image is an independent action from lining up the eyes and does
not contribute to the 3D effect, just the clarity. This is known as
focusing. The brain then measures the angle between the eyes and using
simple trigonometry, calculates the distance to the object in focus. The
point at which the two images overlap is called the focal point and the
distance is referred to as the focal distance.
The two pictures below show how the eyes normally see an image on a
monitor. The right-hand '3-D' seen by the right eye overlaps with the
right-hand '3-D' seen by the left eye (same for the left-hand one) and
the brain locks the eyes as the image is focused. The diagram on the left
shows the angle between the eyes whilst focusing on a screen image. The
diagram on the right shows what the brain sees and what distance it
perceives it to be.
screen ________3-D___3-D________ ________3-D___3-D________
.
. .
. .
. .
eye level <O> <O> <O> <O>
The problem for the brain is that it can only focus by comparing the
two images that it sees. It needs two images of an object to focus upon it
properly (making it difficult to focus on a point in mid air). Normally,
the brain is only presented with two images of each object, so is able to
overlap them easily. It is when the brain is unable to decide at what
point the images should overlap that it can be fooled.
As stated earlier, aligning the two eyes onto an object and obtaining a
sharp image are separate functions for the brain. This means that the eyes
can view an object clearly without locking onto it.
If we use the same two images as above, the brain will normally focus
correctly on the screen. However with a little training, it is possible to
let the eyes 'drift' outwards, so that they are effectively focusing on a
point *behind* the screen.
The best way to learn how to 'unfocus' is to stand at arms' length in
front of a wall, keep your elbows against your chest and hold both hands
in front of your face, with both index fingers extended vertically.
If you focus on your fingers, _ _
you should simply see them both |_| |_|
as shown on the right. The wall |L| |R|
behind will be blurred and out | | | |
of focus. Solid Solid
Now focus on the wall. You will _ _ _ _
probably see four translucent |_| |_| |_| |_|
(semi-transparent) fingers (don't |L| |L| |R| |R|
worry, they're alright!). This is | | | | | | | |
because the brain is now aligning
the images of the wall instead of Translucent Translucent
your fingers.
Next, keep focusing on the wall, _ _ _
but step backwards or forwards |_| |_| |_|
until the two centre fingers meet |L| |L| |R|
and overlap, forming a solid finger | | |R| | |
in the middle. Even though you are
still looking at the wall, it should ^ ^ ^
be possible to see the 'combined' | Solid |
finger clearly. '-Translucent-'
It is this skill, being able to look behind an object but still keeping
it in focus, that allows the brain to be fooled into seeing 3D pictures.
Returning to our screen with our new-found (and practiced!) skill, we
allow the eyes to focus behind the screen as shown below. Initially, the
brain sees two different images. However, as the eyes focus further back,
the right-eye's view of the left-hand '3-D' and the left-eye's view of the
right-hand '3-D' overlap (Yes, go back and re-read that again!). At this
point the brain becomes confused. It sees a solid combined image at the
centre of its vision (the only bit it is interested in) despite the rest
of the image being jumbled. If the viewer holds his or her eyes in that
position, the brain simply resolves the paradox by deciding that it has
locked on correctly to the object in front.
virtual screen ________3-D___3-D________
.
. . 3D image-> 3-D
real screen ________3-D___3-D________
. .
. .
. .
. .
eyes <O> <O> <O> <O>
Now convinced that it has the correct lock-on angle, the brain will
focus the eyeballs for a clear image and then recalculate the distance to
the object, but with an incorrect angle. Because the eyes are at a wider
angle, *everything* appears further back (although it might not seem that
way) but more importantly, the combined image appears in front of all the
other screen images - the brain appears to view everything unfocused as
being even further back.
It is worth noting again that crossing your eyes achieves a 3D effect
in reverse. This is not advised because the eyes have difficulty in
focusing on the two images and if the wind changes, you'll stay that way!
And now...
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