Hello!

What is a concise and preferred way to apply transformation to instance of ParametrizedLine class?
Something like Hyperplane::transform.

Ok, lets look at some code:

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#include <Eigen/Geometry>
#include <iostream>

int main()
{
  using namespace Eigen;
  // line
  ParametrizedLine<double, 3> line(Vector3d(0, 0, 0), Vector3d(1, 0, 0));
  // transformation
  Affine3d transform = Affine3d::Identity();
  transform.rotate(AngleAxisd(EIGEN_PI/2, Vector3d(0, 0, 1)));
  transform.translate(Vector3d(1, 2, 3));
  // apply transformation to line
  line.origin() = transform*line.origin();                // <== any way to simplify this?
  line.direction() = transform.linear()*line.direction(); //
  // print transformed line
  std::cout << "origin: " << line.origin().transpose()
            << "\ndirection: " << line.direction().transpose() << std::endl;
}


Is there any more concise way?

Nothing shorter for now, but feel free to propose a patch adding ParametrizedLine::transform methods similar to HyperPlane::transform with respective unit tests in test/geo_parametrizedline.cpp.

Hello, here is the proposed patch.

Thank you for the patch. For the record, it is now applied in the default branch.

By the way I have a question about Hyperplane::transform implementation. Lets look at this code:

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#include <Eigen/Geometry>
#include <iostream>

using namespace Eigen;

int main()
{
  Vector3d a(1, 0, 0);
  Vector3d b(0, 1, 0);
  Vector3d c(0, 0, 1);
  Vector3d z(0, 0, 0);
  auto p = Hyperplane<double, 3>::Through(a, b, c);
  auto print = [&] {
    std::cout << "normal: " << p.normal().transpose()
              << ", norm: " << p.normal().norm()
              << ", dist: " << p.signedDistance(z) << std::endl;
  };
  print();
  auto t = Affine3d::Identity();
  t.scale(0.5);
  p.transform(t);
  print();
}


It prints the following to screen:

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normal: -0.57735 -0.57735 -0.57735, norm: 1, dist: 0.57735
normal: -1.1547 -1.1547 -1.1547, norm: 2, dist: 0.57735

Here we apply scaling transformation to Hyperplane and the resulting plane doesn't have unit normal vector. It leads to incorrect distance calculation from transformed plane to a point. Is this correct behavior?

You are right, it is missing a normalized.

Fixed in default, 3.3, and 3.2