Hi,

I'm trying to overwrite the rotational part of a given Affine3d transformation with a custom Matrix3d.

Here is an example:

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Affine3d transformation=Affine3d::Identity();
transformation.translation() = Vector3d::UnitY(); //Here is everything ok

// but when I try this:
transformation.rotation() = AngleAxis<double>aa(M_PI/6,Vector3d::UnitX());


This doesn't compile, and I understand why, but I'm wondering if in the Affine3d transform is possible to reference directly the Matrix3d part (which is the top left corner of the 4x4 matrix)

I must use a workaround for this code:

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transformation.matrix().topLeftCorner<3,3>()=AngleAxis<double>aa(M_PI/6,Vector3d::UnitX()).toRotationMatrix();


but I think this is very ugly and probably slower...

Is there a simpler way to modify directly the rotational part of the affine transformation? Documentation doesn't say much about this argument...

Thanks in advance, and again compliments for the spectacular library!

The answer is here under the Geometry Tutorial.
http://eigen.tuxfamily.org/dox/TutorialGeometry.html

Just concatenate your affine operations:

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Transform<float,3,Affine> t = Translation3f(p) * AngleAxisf(a,axis) * Scaling3f(s);

Waxwing wrote:The answer is here under the Geometry Tutorial.
http://eigen.tuxfamily.org/dox/TutorialGeometry.html

Just concatenate your affine operations:

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Transform<float,3,Affine> t = Translation3f(p) * AngleAxisf(a,axis) * Scaling3f(s);

Ok, I know this can be a solution but I didn't want to create a temporary here, only overwrite a piece of a matrix with another given matrix..

linello wrote:

Waxwing wrote:The answer is here under the Geometry Tutorial.
http://eigen.tuxfamily.org/dox/TutorialGeometry.html

Just concatenate your affine operations:

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Transform<float,3,Affine> t = Translation3f(p) * AngleAxisf(a,axis) * Scaling3f(s);

Ok, I know this can be a solution but I didn't want to create a temporary here, only overwrite a piece of a matrix with another given matrix..

Ok, I found the solution:

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transformation.linear() = (AngleAxis<double>(M_PI/6,Vector3d::UnitY())*AngleAxis<double>(M_PI/6, Vector3d::UnitX())).toRotationMatrix();


This acts only on the linear part of the transformation, that in the case of an Affine transformation is the rotation

Good.

Btw, you can use AngleAxisd instead of the more cumbersome AngleAxis<double>.

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transformation.linear() = ( AngleAxisd(M_PI / 6, Vector3d::UnitY()) * AngleAxisd(M_PI / 6, Vector3d::UnitX()) ).toRotationMatrix();