| Re: [eigen] Quaternion initialization from Block/segment (Eigen 3 beta 1) |
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- To: eigen@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [eigen] Quaternion initialization from Block/segment (Eigen 3 beta 1)
- From: Gael Guennebaud <gael.guennebaud@xxxxxxxxx>
- Date: Thu, 22 Jul 2010 20:46:54 +0200
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On Thu, Jul 22, 2010 at 6:33 PM, Jens Andersen <jens.andersen@xxxxxxxxx> wrote:
> Eigen::VectorXd myvector;
> Eigen::Quaternion q(myvector.segment(3,4));
>
> I'm not sure whether this method avoids the copy?
To make it compile you have to set the vector length at compile time:
Eigen::Quaternion q(myvector.segment<4>(3));
And indeed this copy the data to a new array. In Eigen3 you can map
external memory as a Quaternion without any copy using Map:
Map<Quaterniond> q(myvector.segment(3,4).data());
or
Map<Quaterniond> q(&myvector(3));
gael