Re: [ggt-devel] Question about EulerAngleZXY, XYZ, ZYX

[Doug M. <mc...@ia...>]

Allen Bierbaum wrote:
> Doug McCorkle wrote:
> 
>> Allen Bierbaum wrote:
>>
>>> Doug McCorkle wrote:
>>>
>>>> Allen Bierbaum wrote:
>>>>
>>>>> Allen Bierbaum wrote:
>>>>>
>>>>>> Unfortunately, it looks like there are some bugs in the conversion 
>>>>>> somewhere.  My guess is that there are some border cases in the 
>>>>>> extraction of the euler angles from the Matrix.
>>>>>>
>>>>>> I have added a new test case that exhaustively tests all Euler 
>>>>>> getting and setting to find these issues. The test can be found in 
>>>>>> the MatrixGenTest test case.  If anyone has some time to look into 
>>>>>> this, you can use this test case to reproduce the problem.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> I just commited some changes that should fix the errors. (at least 
>>>>> it fixes the ones the test case found :)
>>>>>
>>>>> Give it a spin and let me know.
>>>>>
>>>> Just do a cvs checkout I assume?
>>>>
>>> Yep.
>>>
>>>> Thanks for the prompt response. This was going to be my evening 
>>>> project but I guess I can do some testing instead. I appreciate the 
>>>> help.
>>>
>>>
>>>
>>>
>>> I wasn't planning on working on it, but I had some down time waiting 
>>> for some builds and I found a good solid algorithm in a reference so 
>>> I just gave it a try.
>>>
>> Ok. It appears that things are better but not quite right. If 
>> rotations are purely about an individual axis X,Y,Z everything works 
>> fine. If rotations become compounded things begin to act odd. This 
>> affect may be due to us not understanding how rotations are applied in 
>> OSG though so I would like to do more testing. Some things do appear 
>> to working better but one odd thing did occur. With EulerXYZ under the 
>> old version of gmtl  the compound rotations appeared to work correctly 
>> no mater what had been done. This does not appear to be working now. I 
>> will continue to test and try to provide better feedback.
> 
> 
> One point of feedback.  Because Euler angles are non-unique, sometimes 
> the angles returned do not appear to be continuous.  There is really no 
> way around this.  The test code I wrote sets a matrix using a set of 
> euler angles and then extracts the euler angles and uses the extracted 
> eulers to make a new matrix.  Then it tests if the two matrices are 
> equal.  Note, that this does not require that the original euler values 
> and the extracted euler values must match.  It only requires that the 
> values are functionally equivalent.  The test shows that this works for 
> all angles in the range of -190 degrees to +190 degrees for x,y, and z 
> in all 3 euler types.
> 
That is what I am seeing. The angles are not continuous. Is there a 
better way to handle this? I need to extract rotations for XYZ out of a 
matrix. I thought that EulerAngle would be the best way. Is there a 
better way?

> -Allen
> 
>>
>>> -A
>>>
>>>>
>>>>> -A
>>>>>
>>>>>>
>>>>>> -Allen
>>>>>>
>>>>>> Doug McCorkle wrote:
>>>>>>
>>>>>>>  Hello,
>>>>>>>      When using gtml I noticed that when I pass an identity 
>>>>>>> Matrix44f into
>>>>>>>  make< gmtl::EulerAngleZXY >( identity ) that I get back 90,0,90. 
>>>>>>> If I
>>>>>>>  ask for an EulerAngleXYZ I get back 0,0,0 and ZYX return 0, nan, 
>>>>>>> 0. Is
>>>>>>>  this the correct behavior of EulerAngle? I thought that no 
>>>>>>> matter what
>>>>>>>  Euler combination that I ask for should return 0,0,0 for an 
>>>>>>> identity
>>>>>>>  matrix. Thanks for the help in understanding this better. I am 
>>>>>>> using
>>>>>>>  gmtl 0.4.5.
>>>>>>>
>>>>>>>