On Tue, 09 May 2000 16:25:15 +0200, Sigmund Kyrre Aas
<as### [at] studntnuno> wrote:

>Actually it's 120 times per second.. Ok I'll go away :)

Actually, a common houshold lamp can't flash that quickly. The
filament won't cool off enough between the rapid pulses of current. So
this isn't purely a simple case of Persistence Of Vision, it's also
partially a case of "Persistence of Illumination" as well.

Later,
Glen Berry

( Remove the "7" from 7no### [at] ezwvcom to email me. )

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Glen Berry wrote:
> 
> Actually, a common houshold lamp can't flash that quickly. The
> filament won't cool off enough between the rapid pulses of current. So
> this isn't purely a simple case of Persistence Of Vision, it's also
> partially a case of "Persistence of Illumination" as well.

Go to the movies for a better effect ;) Actually I had a lab project with a
light sensing thing and an oscilloscope some years ago. We could easily
identify the variation of the light from a light bulb. A gas lamp produced a
very weird noise curve.

sig

(followup to off-topic)

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Dear Folks,

Peter wrote:
[snip]
> what *is* persistence of vision?

Ken wrote:
[snip]
> Let us use an example to describe the persistence of vision effect.
> ...The reason the light appears persistent is because
> the light receptors in our eyes cannot react quickly enough to
> resolve the individual on off cycles.

This is a very clear explaination of this effect.  But, to continue this
off-topic discussion, why did the creators of this renderer choose this
name for the program that is mostly used to produce still life
snapshots?

This is a question that people have asked me after I've explained
ray-tracing.

Blessings,
          Brendan

-- 
Michael Brendan Hurley
POV: http://www.geocities.com/mbrendanh/
FAMILY: http://www.saber.net/~mbhcgc/
mbh### [at] sabernet

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Brendan Hurley wrote:

> This is a very clear explaination of this effect.  But, to continue this
> off-topic discussion, why did the creators of this renderer choose this
> name for the program that is mostly used to produce still life
> snapshots?

A good question. I'll see if I can find out.

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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Ken wrote:

> I used the example for purely illustrative purposes. Obviously is does
> take a filament time to cool down and in fact they are specifically
> designed not to. But if we were to model the filament to have a perfect
> heat discharge that followed the current cycle through it in the form
> of a shape edged square wave the example would fit the explaination.
> LED's in fact come much closer and that is why I also mentioned them
> in my example. I just didn't expect you to come along and nit pick.
> If you have a better example to offer I am sure Peter would be happy
> to hear it.

IMAX projector
how's that ;)

> Not on a 30hz system.

-?- where do you have 30Hz?

--
David Fontaine     <dav### [at] faricynet>     ICQ 55354965
Please visit my website: http://www.faricy.net/~davidf/

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Brendan Hurley wrote:

> This is a very clear explaination of this effect.  But, to continue this
> off-topic discussion, why did the creators of this renderer choose this
> name for the program that is mostly used to produce still life
> snapshots?

Artistic license.

--
David Fontaine     <dav### [at] faricynet>     ICQ 55354965
Please visit my website: http://www.faricy.net/~davidf/

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David Fontaine wrote:

> > Not on a 30hz system.
> 
> -?- where do you have 30Hz?

As an electronics engineer I can create just about any duty cycle I
want :)

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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Ken wrote:
> 
> Brendan Hurley wrote:
> 
> > This is a very clear explaination of this effect.  But, to continue this
> > off-topic discussion, why did the creators of this renderer choose this
> > name for the program that is mostly used to produce still life
> > snapshots?
> 
> A good question. I'll see if I can find out.

Here follows two quotes on the subject.  The first is a reply by 
Chris Young, after I told him about Varley's "Persistence of Vision"
I found on a flea market.

************************************************************************************************************
Varley is one of my favorite authors and I've owned that book long
before POV-Ray existed.  POV-Ray was originally going to be called
Starlight or StarLite or something similar but somebody else, I don't
know who, said we'd get in trademark trouble over some existing
product.  Drew Wells was team leader and he picked Persistence of Vision
based on the properties of the human visual system. I also felt there
was a double meaning in that POV-Ray was the continuation (or
persisence) of David K. Buck's DKB-Trace.  I warned Drew about Varley's
book but book titles aren't as messy as product names.  Note also that
Public Broadcasting System has a documentary series called POV but that
stands for Point Of View which is the filmmaking term for hand-held
camera, cinema-verite style used in many documentaries.

I wanted to take our team name from the Fractint Stone Soup Group and
call us the Crystal Soup Group but I got voted down.
        Chris Young, POV-Team Coordinator

************************************************************************************************************
After the recent thread on the starting time I POV-Ray I did
a search and found this post to this very news group from
David Buck himself. The message places the birth of the POV-Ray
project to be in May of 1991. A very historic event!

I hope I'm not stepping on toes by re-posting
it  :-)

Harold

Sun, 19 Feb 1995 19:14:44 GMT
(STEERPIKE) says:
>        I had always presumed that Persistance of Vision was a
>pun on the name of Salvador Dali's painting "The Persistance of Memory".
>Is this right, and if not, how did POV-Ray come to have such a poetic
>name? :)

The POV-Ray project started in May 1991 when I first proposed the idea
to a group of people on CompuServe.  They liked my DKBTrace raytracer
but didn't like the fact that I was too slow adding new features to
it.  They were going to re-write a raytracer from scratch, but I
suggested that after version 2.12 of DKBTrace, they could take the
code as is and develop it from there into a new raytracer.  The first
name was STAR - an acronym for something or other.  Then someone in
the group came up with "Persistance of Vision".  We liked it because
of its reference to Dali (I believe the painting was actually called
Persistance of Vision - am I mistaken?).  Moreover, it seemed to
symbolize the team who "Persisted" to achieve their "Vision".  The
third reference was to the phychological effect that seeing an image
flashed on a screen causes you to retain that image in short term
memory.  Thus, your memory was a representation of reality but not
really reality.  They all seemed to fit together to make a nice name.
Early on, we were abbreviating the name to PVRay, but we were
concerned about a commercial product called PV-Wave.  We agreed to
change the abbreviation to POV-Ray and standardize on the spelling.

>David Buck dbu### [at] ccscarletonca
************************************************************************************************************

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Fabien Mosen wrote:
> 
> Ken wrote:
> >
> > Brendan Hurley wrote:
> >
> > > This is a very clear explaination of this effect.  But, to continue this
> > > off-topic discussion, why did the creators of this renderer choose this
> > > name for the program that is mostly used to produce still life
> > > snapshots?
> >
> > A good question. I'll see if I can find out.
> 
> Here follows two quotes on the subject.  The first is a reply by
> Chris Young, after I told him about Varley's "Persistence of Vision"
> I found on a flea market.

Thank you for posting this. It's amazing what people will archive away
waiting for that obscure moment at some future time when it might be
needed.

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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Ken wrote:
> 
> Brendan Hurley wrote:
> 
> > This is a very clear explaination of this effect.  But, to continue this
> > off-topic discussion, why did the creators of this renderer choose this
> > name for the program that is mostly used to produce still life
> > snapshots?
> 
> A good question. I'll see if I can find out.

Yes. When I first heard of POV-ray, I thought the POV stood for
Point Of View. Still seems more appropriate than Persistence Of Vision.

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