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Showing posts from January 10, 2010

Euler Angles And Gimbol Lock

perm url with updates: http://xahlee.org/math/gimbol_lock.htmlEuler Angles And Gimbol LockAm reading Second Life's doc about rotation (at Source). One interesting thing it mentioned is this:The main advantage of using quaternions is that they are not susceptible to gimbal lock.That is interesting. Look at Wikipedia about gimbol lock: Gimbal Lock. The essence is that, simple gimbols system cannot track motion continuously in some situations. For example, suppose you have a telescope. The base can rotate around freely, and the scope can rotate up and down. If you track some flying object that flew from eastern horizon to directly above your head (noon sun), and then suppose it made a sudden change of direction towards north, then your telescope will have problem to follow it. You'll have to twist the base 90° first before you can move the scope down.The continuous tracking is important in many applications. Suppose your telescope is a gun turret, and the flying object is a ufo y…

fraud in physics; academic review system

Discovered: Jan Hendrik Schoen, “biggest fraud in physics in the last 50 years”.I discovered this from this blog Three myths about scientific peer review (2009-01-08) by Michael Nielsen Source. Michael Nielsen turns out to be a known writer who was a academic in physics. Some of the more interesting articles i found in his blog are: Quantum computing for everyoneSource, Why the world needs quantum mechanicsSourceSee also Wikipedia Quantum computer etc.

Avatar movie review

perm url with updates: http://xahlee.org/Periodic_dosage_dir/skina/avatar.htmlAvatar (film) ReviewXah Lee, 2010-01-07Went to watch the movie Avatar (2009 film) in theater today.Boo. On a scale of 1 to 10, i'd say this is no more than 7. This is totaly predicable, steoreotypical, intellectually shallow. The 3D effect isn't impressive at all, and about the only thing that is positive about this movie is the imaginative floura and fauna.This movies garnered raving reviews, both by critics as well as being a highly successful money maker. But it's so disappointing to me that i have to think about where to begin.3D EffectOk, lets begin at some easy criticisms, the 3D tech. I recall, back in late 1970s or early 1980s when i was about 10 or so, my mom's mom took me to see one of the first 3D film, in Taiwan, a kung fu film. I vividly recall that i literally dodged when the weapons swung towards me from the screen. Yeah, a lot people did that. That, is the effect of good 3D on…