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

[Allen B. <al...@vr...>]

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.

-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.
>>>>>>
>>>>>>
>>>>>>  Doug
>>>>>>
>