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:
>>>>
>>>>> 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?
> 
> 
> Depends upon why you need them to be continuous.  You could always use 
> Quaternions if you needs something that has numbers that look more 
> continuous.
> 
Well, functionally should be ok it just doesn't appear that that is what 
is happening. I think I may be messing up how OSG is expecting the 
angles to be applied to the transform. I need to do more testing. Thanks 
again for the help.

Doug

> -Allen
> 
>>
>>> -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.
>>>>>>>>>
>>>>>>>>>
>>
>