CGTalk Calculate angle from vector.
 05-17-2013, 06:38 AM #1 Tawashi New Member portfolio Masanori Tsutsumi Tokyo, Japan   Join Date: Jun 2009 Posts: 1 Calculate angle from vector. Hi,I'm trying to calculate angle from vector. It seems simple. my test code is here: Code: ``` proc test(){ vector \$a = <<0, 1, 0>>; vector \$b = <<0.5, 0.5, 0>>; float \$c = \$a * \$b; float \$mag_a = mag(\$a); float \$mag_b = mag(\$b); float \$theta = (\$a*\$b)/(\$mag_a * \$mag_b); \$theta = \$theta * 180 / 3.14; print ("theta = " + \$theta + "\n"); }test;``` [result] theta = 40.53478363 I think it`s 45.0 in mathematically,but The result ange is uncorrect. It`s nearly 45.0 . Is there are any items missing? or formula is uncorrect? Please give me advice. Sorry for my poor English. share quote
 05-27-2013, 01:52 PM #2 hazmondo Expert   portfolio Harry Rigging TD Axis Animation Glasgow, United Kingdom   Join Date: Jan 2013 Posts: 329 Hello, It seems like your saying that θ = (a*b)/(|a|*|b|) but that equation is incorrect, the correct equation is cosθ = (a*b)/(|a|*|b|) --> θ = arccos((a*b)/(|a|*|b|)). Hope this helps, -Harry Last edited by hazmondo : 05-27-2013 at 07:00 PM. share quote
 06-15-2013, 02:14 PM #3 ogbonna Veteran portfolio Nathaniel Anozie Baltimore, USA   Join Date: Dec 2008 Posts: 70 Hi, if using Maya might want to checkout the built-in angleBetween Node or MEL/Python command. Hope this is helpful. Cheers! -Nate share quote
 06-21-2013, 10:40 PM #4 DangerAhead Rigger Lover   portfolio Geordie Martinez Character TD - Rigger - Massive TD Industrial Light & Magic San Francisco, USA   Join Date: Jun 2003 Posts: 437 PyMEL could really clear this up in a quick way. here is what you were doing. it was indeed 45 degrees: Code: ``` import pymel.core as pm # make vectors vec1= pm.dt.Vector(0,1,0) vec2= pm.dt.Vector(0.5,0.5,0.0) # get angle between in radians radians = vec1.angle(vec2) #get degrees degrees = pm.dt.degrees(radians)``` __________________ animrig.com Check out my "Intro to PyMEL Training Video" at cgcircuit.com -- maya python the OOP way! share quote
 06-21-2013, 10:40 PM #5 CGTalk Moderation Lord of the posts   Join Date: Sep 2003 Posts: 1,066,479 Thread automatically closed This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum. __________________ CGTalk Policy/Legalities Note that as CGTalk Members, you agree to the terms and conditions of using this website. share quote