Metal Detector Animation

[Ena Marklund]

Mypuppet's arms do not seem to be responding correctly to the limb ik behavior - they are not bending as expected. When I move the arms up, the forearm show switches to pointing up. It kind of works when I drag the arm toward the body. Also, the limb ik seems to affect each arm separately. This could be because my arms are not exactly identical. Side note: is it possible or useful to put the ik limb behavior separately on each arm if they need different settings?

That works! I wish I understood how Limb IK work "under the hood", then I'd have a better understanding of how the tweaking affects performance. I'm not always a big fan of twisting and sliding things until something works. lol.. Do you have any advice about your thinking that led you to these settings?

I, 100% agree, CA is like navigating a field of land mines without a metal detector. Animation takes a long time, as we all know, and spending weeks, days, or even hours, troubleshooting (moving sliders, moving behaviors from one part to another, adjusting origin points, etc,) with zero documentation is a workflow killer. Not to mention the slow processing of every action. Even just clicking undo on a fast rig takes like 5 secs. There needs to be documentation of the theory and logic of building puppets. Just like with anything else. You don't sit down to do calculus without knowing it or being instructed. You are basically forcing users to "write the rules" for you. You did this in the early years of Flash and it was a nightmare. Make developer style documentation, not videos on how to use the premade puppets. We all want to know how it works under the hood so we can have formed logic to our processes and workflows. Some of us don't want to play with the software, some of us want a tool that HELPS us achieve our goals. In it's current state, CA is nothing more than a toy.

Also noticed in the Limb IK tutorial, Dave showed his method for dialing in the elbow flip threshold. He put the puppet in a T pose then started adjusting the elbow flip threshold. At a certain point, the elbow began to bend and this became his setting. When I try this, my puppet's arms don't respond at all no matter which direction or how much a adjust the elbow flip threshold. By the way, he had his IK limb behavior on the puppet layer instead of each arm (I've tried both).

I'm using a technique where you extend the arm at different angles and drag the hand inward toward the shoulder. (Here's a video screen capture) This will reveal any problem areas, which you can then adjust bend strength or elbow flip threshold ... whichever one has the most effect. In this case, it was bend strength. (this is actually an improvement to the last settings I sent)

I know this is an older post, but it helped me solve a similar issue now that Body Tracker is out, so thanks. Because I had the shoulders tagged in Body and not in the arms, Limb IK wouldn't work correctly. It needs shoulders, elbows and wrists in the arms, while Body Tracker needs them (or at least some of them) in the Body. So I tagged the arm origin points as shoulders too, and everything's fine.

You Literally saved me so much stress! I couldn't figure it out because I watched a tutorial saying to tag the body as left/right shoulder. I did what you did and tagged it in the arms as well and now it works! Thank you!

THIS!!!! Most of the videos seem to be giving me misinformation. Adding shoulders and hips to the body didn't work. Adding them to the limbs did. I also discovered that adding handles to the legs doesn't work, but adding them to the body does. Can someone on the CA dev team write up some documentation explaining all of this stuff?

If you've ever made an electromagnet by wrapping a coil of wirearound a nail and hooking it up to a battery, you'll know thatmagnetism and electricity are like anold married couple: whenever you find one, you'll always find the other, not very far away.

Different metal detectors work in various different ways, but here'sthe science behind one of the simpler kinds. A metal detector contains acoil of wire (wrapped around the circular head at the end of thehandle) known as the transmitter coil. When electricity flowsthroughthe coil, a magnetic field is created all around it. As you sweep thedetector over the ground, you make the magnetic field move aroundtoo. If you move the detector over a metal object, the movingmagnetic field affects the atoms inside themetal. In fact, itchanges the way the electrons (tiny particles "orbiting" aroundthose atoms) move. Now if we have a changing magnetic field in themetal, the ghost of James Clerk Maxwell tells us we must also have anelectric current moving in there too. In other words, the metal detectorcreates (or "induces") some electrical activity in the metal. But then Maxwell tellsus something else interesting too: if we have electricity moving in apiece of metal, it must create some magnetism as well. So, when youmove a metal detector over a piece of metal, the magnetic fieldcoming from the detector causes another magnetic field to appear aroundthe metal.

It's this second magnetic field, around the metal, that the detector picks up.The metal detector has a second coil of wire in its head (known asthe receiver coil) that's connected to a circuit containing aloudspeaker. As you move the detectorabout over the piece of metal,the magnetic field produced by the metal cuts through the coil. Nowif you move a piece of metal through a magnetic field, you makeelectricity flow through it (remember, that's how a generator works).So, as you move the detector over the metal, electricity flowsthrough the receiver coil, making the loudspeaker click or beep. Heypresto, the metal detector is triggered and you've found something!The closer you move the transmitter coil to the piece of metal, thestronger the magnetic field the transmitter coil creates in it, the stronger themagnetic field the metal creates in the receiver coil, the more current thatflows in the loudspeaker, and the louder the noise.

As we saw up above, magnetic fields are produced by changing electric fields, which oscillate at a particularfrequency. Different frequencies give better or worse results depending on what kind ofmetal you're looking for, how deep in the ground you're searching, what kind of material the ground is made from(sand or soil or whatever), and so on.

Photo: This foldable VLF mine detector (a US Army Vallon VMW1) can be used on land or underwater at depths up to 30m (100ft). Photo by Kimberly Trumbull courtesy of US Army, published on Wikimedia Commons.

Photo: Clearing mines. This army mine detector (a CyTerra AN/PSS-14) combinesa super-sensitive, pulsed metal detector and a ground-penetrating radar (GPR) in a single,handheld unit. It can detect mines with low metallic content and distinguish between mine metal, irrelevant metal clutter, and soil with high metal content. Photo courtesy of US Army published on Flickr under a Creative Commons (CC BY 2.0) licence.

Metal detectors aren't just used to find coins on the beach. Youcan see them in walk-through scanners at airports (designed to stoppeople carrying guns and knives onto airplanes or into other secureplaces such as prisons and hospitals) and in many kinds of scientificresearch. Archeologists often frown on untrained people using metaldetectors to disturb important artifacts but, used properly and withrespect, metal detectors can be valuable tools in historic research.

Photo: This wand-type detector, called a SuperScanner and made by Garrett Metal Detectors,is being used to check people at a traffic control point in Iraq.It runs off a built-in 9-volt battery that provides about 60 hours of continuous operation.If you find metal, the detector lets you know with a combinationof flashing LED lights and a warbling noise.It's 42cm (16.5 in) long and weighs 500g (17.6 oz).Detectors like this cost about $200 (100).Photo by Ali Hargis courtesy of Joint Combat Camera Center Iraq and DVIDS.

Metal detectors apparently date back to the shooting of US President James A. Garfield in July 1881. One of the bullets aimed at the President lodged inside his body and couldn't be found. Telephone pioneer Alexander Graham Bell promptly cobbled together an electromagnetic metal-locating device called an induction balance, based on an earlier invention by German physicist Heinrich Wilhelm Dove.Although the bullet wasn't found and the President later died, Bell's device did work correctly, and many people credit it as the very first electromagnetic metal locator.

Artwork: Left: Find that bullet! This sketch by William A. Skinkle, from Frank Leslie's illustrated newspaper of August 20, 1881, shows rather a lot of doctors (!) using Bell's induction balance to find the bullet lost in the President's body. The room on the left contains the equipment, on the table-top, which is labelled "interrupter," "condenser," and "battery" (the boxes at the back of the table). You can just make out wires that stretch around the bottom of the picture through to the President's bed on the right. Presumably Alexander Graham Bell is the bearded man talking on the telephone on the right?Courtesy of US Library of Congress.

Artwork: The Metalloscope patented by Gerhard Fischer (Fisher) in 1937, which I've colored to make it easier to follow. The transmitter coil is in the red box at the front; the receiver coil is in the blue box at the back. The transmitter uses inaudible 30,000 Hz signals; the receiver sends out audible signals (with a frequency of about 500 Hz) to headphones, as in a modern metal detector. The transmitter and receiver coils are mounted at right angles to one another so the receiver doesn't pick up signals directly from the transmitter. Artwork courtesy of US Patent and Trademark Office.

Treasure hunters will always value metal detectors like these because, historically, valuable things were usually made of metal.But in the world of security, it's no longer enough to rely on metal detectors as our sole line ofdefence. The kinds of people who like to smuggle weapons through security, for example, are well awarethat they'll have to walk through metal detectors, and they're likely to try alternatives like ceramic,plastic, or carbon-fiber knives. Although reputable manufacturers do take pains to ensure there are small metallic parts in the handles of "non-metallic" knives, for exactly this reason, there's nothing to stop anyone sharpening a piece of plastic toimprovize a knife, as the police have repeatedly found. How, then, do we detect nonmetallic threats?

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