[Raytrace] Raytrace List Origins (Long)
John D. Upton
jd-upton@texas.net
Thu, 06 Dec 2001 18:17:58 -0600
List Members,
Welcome.
As background material, I am posting excerpts from some of the
off-line email conversations that lead to the generation of this list. My
cuts of non-pertinent material are denoted by "[snip]".
Ken Lowther was the driving force behind getting the list started. I
didn't find out about being appointed list administrator until after the
list was created. Thanks Ken. (...I think...) To repay the honor(?), my
first duty was to make Ken alternate administrator. :^)
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At 12:55 PM 11/27/01 -0500, Ken Lowther wrote on the ATM List:
>Please consider 'donating' your spec files to the atm site so that others
>can use them for reference. Having these files could be a useful starting
>point for some of us that are less adept at these programs.
At 07:57 AM 11/28/01 -0600, John D. Upton wrote off-list:
> I don't mind sending you the OSLO file I used, but I don't think it
> would be of use to anyone. There are already several OSLO and ZEMAX
> files on the ATM Site. They represent unusual or sometimes "complex"
> designs that may be of use to others. A file describing a single
> paraboloidal mirror for a Newtonian seems of little use to me.
>
> What *is* needed is a set of tutorials for each of OSLO, ZEMAX and
> MODAS that explain how folks can get the information that was discussed
> in this thread on the ATM List. The useful data is not in the file -- it
> is in which buttons you push (and commands you use) to try to get some
> insight into the problem at hand. [snip]
At 05:15 PM 11/28/01 -0500, Ken Lowther wrote off-list:
>[snip] When W=B put out the book on lens design with computers I bought it
>and downloaded OSLO. It was a very frustrating experience. I put a lot
>of time into it with very little in the way of results. Maybe start with
>the Newtonian and see how it goes? If you want to collaborate I can set
>up a quick email group. I'm sure we could get a few people from the list
>to offer input. [snip]
At 04:56 PM 11/29/01 -0500, Ken Lowther wrote off-list:
>I could set up a list and see who is interested in learning a little OSLO
>and seeing if we could turn the most common questions and problems into a
>FAQ or tutorial. If it works fine. If there isn't enough interest, you
>have saved yourself a lot of work. ;-)
At 06:32 PM 11/29/01 +1000, Peter John Smith wrote off-list:
>I have found the level of help provided with Raytracing software as
>pathetic and I fully relate to Ken's comments.
>
>This includes Zemax. [snip] The instructions do tersely cover features
>but one needs much more because one needs to understand how to use the
>program before the terse comments make any sense............
>
>I eventually taught myself to use Zemax (well - a useful portion of its
>features. Doubt anyone could understand all) by using some demo files
>which came with it and a real menagerie of mainly old optics books. [snip]
>
>In my opinion you need
>
>1/ example files of a large range of types of optical instruments. This
>is especially true when the ray path inverts and rays pass some surfaces
>more than once.
>
>2/ some optical background. Preferably a lot. But the ironic thing is
>that a lot of good work can be done with a good modern optimising
>raytracer with limited optics theory.
>
>3/ more specific info on the ways modern raytracers have
>developed. There is almost a set of jargon relating to them. It is not
>in the books to my knowledge and is probably best overcome by good tutorials.
>
>I found the most useful technique to work outwards from example
>files. Then substitute other specs for other example designs available to
>me by modifying these files. The two best books for this I had which gave
>enough examples and some assessment of them were 'Telescope Optics -
>Evaluation and Design' by Rutten and VenRooij and Warren J Smith's
>'Modern Lens Design - A Resource Manual'. Also published designs in S&T
>over the years often gave some assessment as well as specs and were
>generally correct. Smith's book is mainly a collection of Patent Specs
>and some others. It is not on modern design methods. But it includes
>examples of most types of optics designs WITH A SHORT RUNDOWN ON THEIR
>ASSESSMENT which is really valuable. There is also an introduction to the
>book which matched a lot of what I wanted to know. It is not aimed at any
>one raytracer which is a both a limitation and a strength. Being general
>sounds like a good idea but it is amazing how slight variations in the way
>each raytracer presents and accepts info is such a block to a newcomer.
>
>The least useful books were on raytracing theory.
>
>One real trap was that many designs I had collected were simply wrong or
>afflicted with typos. When one has no confidence to recognize this it has
>a huge negative impact. You would be amazed at how many prescriptions are
>bandied around that are simply wrong.
>
>Unfortunately I cannot see a way to solve this problem easily because -
>
>1/ Most top line raytracers with a nice user interface with any
>reputation are expensive and need a dongle to run. Thus there is little
>point in their files being made readily available. Vary few 'free'
>programs include optimisation in a simple enough interface for it to be
>useable. With all of its limitations, OSLO still stands out here as being
>useful. [snip]
>
>2/ Files for one program are not readily available to to others. Despite
>the fact that some will 'import' others files, I have found this of very
>limited use. As raytracers grow in sophistication features are added.
>Unless everyones import features are all updated these now become
>unreadable to many other programs. This is the reason I have not placed
>more files in the ATM space. I have had many requests from people for
>help because they could not import my files and have lately taken more
>to ------.txt files of prescriptions for intercommunication. This is
>pathetic but it always works. Of course the recipient must have enough
>experience to use them. One product I think should be more well known is
>OPTIX which will translate raytracing file formats reasonably. The writer
>has a good simple product and seems to intend extending the freeware LT
>version to a fully optimising program which will then cost a significant
>amount. It is a little like a Zemax lookalike. But, realistically, is
>there room for another professional raytrace on the market. At the moment
>the LT version is useful as a file viewer with some assessment capability
>but unless kept up to date as other programs evolve will lose its usefulness.
>
>At one time I thought of placing files for every design on my web site in
>the ATM space and am willing to do this (partly done) but is it
>worthwhile in Zemax format ? . Every one of my web articles contains a
>txt prescription.
>
>[snip]
>
>As a matter of interest, on the Zemax web site there are many files for
>download.
>
>To download go to: http://www.focus-software.com/file_exchange/
>
>Many of these are of weird setups - things that would take you ages to
>figure out how to set up in the lens editor. In fact, some are people
>showing off their expertise I think. But many could be the basis for
>other work. One set of these files corresponds for all the examples in
>Wilson's books on reflective telescope optics. Maybe we should have links
>to any sites like this in the ATM space..
>
>You can also download a demo version of Zemax which contains many many
>useful examples.
>
>I think a few more 'Tutorials' like that done by John Upton may be useful
>but that requires a huge amount of work. [snip] And all this work may
>become void with changes in the user interface or file structure of the
>raytracing software.
>
>Articles on any design could include some discussion of evaluation
>techniques and the evolution of the design.
>
>As a matter of interest, I have not started a new Zemax file in years. I
>always modify an existing file of something similar. Has its good and bad
>points. Is very easy but sometimes contains an obscure artifact that
>becomes a problem. But it is a powerful approach which suits my lazy
>inclination.
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John D. Upton
Georgetown, TX
<http://www.atm-workshop.com/> "The ATM's Workshop"
<http://members.aol.com/RonWin20/> "Ronchi For Windows Home Page"