Finite State Machines Advice and Finite State Analysis

(New posting on 2016-06-04; originally posted as /archives/4698)

By Dainis (Own work) [Public domain], via Wikimedia Commons
If your business logic starts getting complicated, it might mean that you should use finite state analysis and design. This technique is very popular for the artificial intelligence systems used in video games, and there are a number of finite state machine frameworks out there for Java, but they are all pretty heavyweight.

How does one create a lightweight state machine, and what is finite state analysis anyway? The ACM published a paper called “The Art of the State” by John F. Cigas in 1992.

In the paper Professor Cigas describes how to do finite state analysis, and how to implement your state machines via a loop surrounding a switch statement… that’s it… its that simple.

Please read the paper. If it doesn’t make any sense, then ask me how this is used, and I will show you. Please go to this page to get the PDF: The technique basically orders complex if-this-or-that-or-this-or-that type logic into the simplest form possible, and its really easy to do.

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Lens Compression and Lens Distortion

(Originally published 2016-03-16 as /archives/10930)

This lens-compression-thing: we all agree on it correct?

Lens Compression

The definition of lens compression is this: if you use a longer focal length, then the background will appear to be closer to the subject. There are numerous examples of images that “prove” this out there (including the GIF below), but guess what? Lens compression doesn’t actually exist.

Here’s how the prove-it examples work:

  1. First the photographer makes a photo of a subject, standing in front of a background object, with a short focal length lens (wide angle, less magnification).
  2. Then the photographer takes the same picture, of the same subject, at the same distance from the camera, but with a longer focal length lens (telephoto, more magnification).
  3. Then we compare the two images, and note that the background object appears to be closer to the subject in image #2.Here’s the kicker:
  4. If we then crop image #1, so that the subject takes up the same amount of space in each image, we will note that the subject now looks to be the same exact distance from the background object as in image #2.

In other words: lens compression is just an optical illusion.

Lens distortion

Barrel Distortion, Pincushioning, Bokeh, etc., may be different with each of the two lenses. Generally the wider angle lens (shorter focal length, less magnification) will distort the image more and cause more foreshortening relative to the telephoto lens (longer focal length, more magnification), but not always. A lot depends on lens design, and post processing software is really good at removing distortion these days.

The following GIF was shared at “reddit /r/educationalgifs How different lenses affect portraits“. It shows the foreshortening issue and the so-called-lens-compression-issue at various focal lengths of a telephoto super zoom lens. For many people this will be proof that lens compression is real. It still isn’t real, and not all wide angle lenses will cause such drastic foreshortening.

OK: so if the focal length is changing, then why is the subject’s head mostly the same size? Because the photographer is moving physically closer to the subject, for the wider angle shots, and farther away for the telephoto shots.

Here’s the GIF:
XBIOEvZ - Imgur

Back to the Lens Compression Example

OK, so Paul must be wrong about lens compression. I mean look at how that tree in the background of that GIF moves closer to the subject: right?

In the following video, Dieter Schneider does the steps (from above) to prove that lens compression does not exist.

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The Fastest Woman On Earth Attempt -and- Where Will Our Future Pilots Come From?

(Originally posted Aug 1, 2015 on as /archives/10506)

Here’s a video about becoming the fastest woman on Earth

I dig land speed record videos.

What’s with the fighter-pilot-oxygen-mask?

Is it for cooling (not oxygen) like on a racing helmet?

Pilots use oxygen to fly unpressurized planes at high altitudes. Why do that? If there’s a stronger tailwind up there, then they can save time and fuel. I read a story about a check-delivery-pilot that did this, but became oxygen-deprived by mistake. Most military flying requires oxygen masks too.

A commercial pilot is not what many people think it is.

(The rest of this post is USA-centric.)

The people that fly for the airlines, need an Air Transport Pilot License (ATPL). The ATPL requires 750 to 1500 hours (depending on your training) of flying. The people that we usually call “commercial pilots”, are actually ATPs. The commercial pilots license is different.

Where will our future pilots come from?

That check-delivery-story reminded me of my concerns about where the USA will get its future pilots.

How does a pilot get 750 to 1500 hours of experience, which is just one of the requirements for the ATPL?

  • Delivering our checking-acount-checks from bank-to-bank at night. The “Check 21 Act” of 2003, made it legal to send scans of checks. So no more “flying checks”. Two-billion dollars of flights (per year?) are now gone: “poof”.
  • Fly as an airline co-pilot, but now they also need an ATPL (as-of July 15, 2013).
  • As a flight instructor
  • Charters
  • Corporate aviation
  • Plane rental, but that’s expensive; 1500 hours costs $112,500 to $600,000. (at $75 to $400 per hour for small non-turbine planes).
  • The military
  • Etc.

Without check deliveries, and non-ATP co-pilots, where will get enough pilots with enough hours? I have no idea, but it will become a problem without some future change.

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