JE42 - 8 months ago 23

C++ Question

Is there a shorter way to apply the transform?

`auto vecs = Matrix<float, Dynamic, 3>(); //vector in each row.`

Affine3f transform = ...; // some Affine3 transform

for (int r = 0; r < vecs.rows(); r++) {

Vector3f v = vecs.row(r);

v = transform * v;

vecs.row(r) = v;

}

Answer

@JE42 is right, for loops are almost never necessary with Eigen.
It is certainly possible to simplify. However, note that `transform * v`

in your case is not a simple multiplication but an affine transformation equivalent to `transform.linear() * v + transform.translation()`

. https://eigen.tuxfamily.org/dox-devel/group__TutorialGeometry.html

Also, your "points" are rows, so additional transposes are needed.

In sum, (without actually compiling or testing it) your calculation should be equivalent to

```
vecs.transpose() = (transform.linear() * vecs.transpose()).array() + transform.translation();
```