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On 07/02/2012 09:08 AM, Felix Rehrmann wrote:
<blockquote cite="mid:4FF148D7.4030901@dfki.de" type="cite">
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<div class="moz-cite-prefix">Hi all,<br>
<br>
I would like to propose to have a seperate function like
isUnitQuaternion or similiar.<br>
<br>
One says that the rotation is not set,often because only
position data are transmitted.<br>
The other one is to check only the quaternion, which can also be
non-unit for numeric reasons.<br>
</div>
</blockquote>
Do you have a real use case for non-unit quaternions? I would favour
to use unit quaternions for all base types as convention to remove
another source of errors. In that case I would add the check insight
isValidValue<br>
<br>
Alex<br>
<br>
<blockquote cite="mid:4FF148D7.4030901@dfki.de" type="cite">
<div class="moz-cite-prefix"> <br>
The user then would have the possiblity to decide what he wants
to know. Furthermore<br>
this function could have the accuracy as argument: bool
isUnitQuaternion (double accuracy = 1e-6).<br>
I would guess it could be hard to find a fixed value here. I
would consider some deviation from 1.0<br>
fine for further computation (e.g. like 0.9999something ).<br>
<br>
So long!<br>
Felix<br>
<br>
<br>
Am 29.06.2012 18:43, schrieb Janosch Machowinski:<br>
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<div class="moz-cite-prefix">Uhm, <br>
<br>
fabs(ori.squaredNorm() -1) < 1e-6<br>
<br>
Just as an idea ;-)<br>
Greetings<br>
Janosch<br>
<br>
On 29.06.2012 17:58, Javier Hidalgo Carrió wrote:<br>
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<div class="moz-cite-prefix">On 06/29/2012 05:20 PM, Alexander
Duda wrote:<br>
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<blockquote cite="mid:4FEDC7D6.6010602@dfki.de" type="cite">
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On 06/29/2012 05:02 PM, Javier Hidalgo Carrió wrote:
<blockquote cite="mid:4FEDC387.8010806@dfki.de" type="cite">
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<div class="moz-cite-prefix">+1<br>
Since Orientation is a Eigen::Quaternion we could even
use the norm() method.<br>
<br>
Javier.<br>
<br>
<table class="memname">
<tbody>
<tr>
<td class="memname"><a moz-do-not-send="true"
class="el"
href="http://eigen.tuxfamily.org/dox/classEigen_1_1QuaternionBase.html#a844358c46408e878e60c4026c52eb1e9">Scalar</a>
norm </td>
<td>(</td>
<td class="paramname"><br>
</td>
<td>)</td>
<td> const<code> [inline]</code></td>
</tr>
</tbody>
</table>
<div class="memdoc">
<dl class="return">
<dt><b>Returns:</b></dt>
<dd>the norm of the quaternion's coefficients </dd>
</dl>
<dl class="see">
<dt><b>See also:</b></dt>
<dd><a moz-do-not-send="true" class="el"
href="http://eigen.tuxfamily.org/dox/classEigen_1_1QuaternionBase.html#a8699d72c996ca6cb4673e810fe3a616c">QuaternionBase::squaredNorm()</a>,
<a moz-do-not-send="true" class="el"
href="http://eigen.tuxfamily.org/dox/classEigen_1_1MatrixBase.html#a0be1b433c65ce9d92c81a4718daf54e5">MatrixBase::norm()</a>
</dd>
</dl>
</div>
<br>
</div>
</blockquote>
I think you do not gain so much from this functions as you
will get a scalar which you have to sum anyway. Do you know
if there is a function which checks if the quaternion is
valid?<br>
<br>
</blockquote>
I don't know any valid method. Having no-normalized quaternion
is sometimes common (e.g, passing a quaternion through a EKF)
and normalization needs to be done.<br>
<blockquote cite="mid:4FEDC7D6.6010602@dfki.de" type="cite">
fabs(ori.w()*ori.w()+ori.x()*ori.x()+ori.y()*ori.y()+ori.z()*ori.z()-1.0)
< 1e-6<br>
<br>
</blockquote>
What should be the error threshold to define if a quaternion
is valid or not? Perhaps norm() does some round to 1.00...<br>
<blockquote cite="mid:4FEDC7D6.6010602@dfki.de" type="cite">
Alex<br>
<blockquote cite="mid:4FEDC387.8010806@dfki.de" type="cite">
<div class="moz-cite-prefix"> On 06/29/2012 04:53 PM,
Alexander Duda wrote:<br>
</div>
<blockquote cite="mid:4FEDC16F.7050503@dfki.de"
type="cite">
<pre wrap="">Hi,
the base type samples::RigidBodyState has a function to check if the
orientation is valid.
At the moment it only checks if the values of the quaternion
representing the orientation are different to NaN.
I propose that we also add a check that the quaternion is an unit
quaternion because otherwise wrongly initialised orientations might lead
to strange transformation matrices and vanishing objects in OSG.
Any opinions?
Alex
static bool isValidValue(base::Orientation const& ori)
{
return !base::isNaN(ori.w()) &&
!base::isNaN(ori.x()) &&
!base::isNaN(ori.y()) &&
!base::isNaN(ori.z()) &&
ori.w()*ori.w()+ori.x()*ori.x()+ori.y()*ori.y()+ori.z()*ori.z()-1e6 < 1;
}
</pre>
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<br>
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<pre class="moz-signature" cols="72">--
Dipl.-Ing. Alexander Duda
Unterwasserrobotik
DFKI Bremen
Robotics Innovation Center
Robert-Hooke-Straße 5
28359 Bremen, Germany
Phone: +49 (0)421 178-456620
Fax: +49 (0)421 178-454150
E-Mail: <a class="moz-txt-link-abbreviated" href="mailto:alexander.duda@dfki.de">alexander.duda@dfki.de</a>
Weitere Informationen: <a class="moz-txt-link-freetext" href="http://www.dfki.de/robotik">http://www.dfki.de/robotik</a>
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