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  #1  
Old 03-19-2013, 12:00 PM
mape2k mape2k is offline
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Join Date: Mar 2013
Posts: 60
Varying rotation speed with spinTo

Hello,

I am using the spinTo command in a for loop to spin to different view angles during an experiment. I want the rotation speed to be constant, independent from the actual and desired view angle.
However, the spinTo command gives me different rotation speeds when I use it. Sometimes its faster, and sometimes its slower, even though I specify a constant speed angle.

I have attached a working minimum example. Here, the speed will vary, seemingly at random.

Code:
import viztask
import viz
import vizact

angles = [-120,150,100,150,-170,50,90,150]

viz.addChild('piazza.osgb')
view=viz.MainView

def run():
	
	for k in angles:
		print str(k)
		yield viztask.waitKeyDown(' ')
		yield viztask.addAction(view, vizact.spinTo(euler=[k,0,0],speed=80,interpolate = vizact.linear))

viztask.schedule(run())
viz.go()
Thank you for your help in advance!
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  #2  
Old 03-20-2013, 09:23 AM
farshizzo farshizzo is offline
WorldViz Team Member
 
Join Date: Mar 2003
Posts: 2,849
This appears to be a bug with how the rotational differences are computed. It doesn't seem to be using the shortest distance in all cases. This will be fixed in the next release. In the meantime you can add the following code to the beginning of your script to get the correct behavior:
Code:
import math
import vizmat
def QuatDiff(q1,q2):
	w = abs((vizmat.Quat(q1) * vizmat.Quat(q2).inverse()).w)
	return viz.degrees(math.acos(w) * 2.0)
vizmat.QuatDiff = QuatDiff
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  #3  
Old 03-22-2013, 08:48 AM
mape2k mape2k is offline
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Join Date: Mar 2013
Posts: 60
Thank you for your quick reply and the hot-fix!
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